[v3,1/2] dt-bindings: watchdog: Add Spreadtrum watchdog documentation

This patch adds the documentation for Spreadtrum watchdog driver.

Signed-off-by: Eric Long <eric.long@spreadtrum.com>
Acked-by: Rob Herring <robh@kernel.org>
---
Changes since v2:
- Add acked tag from Rob.

Changes since v1:
- No updates.
---
 .../devicetree/bindings/watchdog/sprd-wdt.txt         | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/sprd-wdt.txt

On 10/26/2017 07:28 PM, Eric Long wrote:
> This patch adds the watchdog driver for Spreadtrum SC9860 platform.
> 
> Signed-off-by: Eric Long <eric.long@spreadtrum.com>
> ---
> Change since v2:
>   - Rename all the macors, add SPRD tag at the head of the macro names.
>   - Rename SPRD_WDT_CLK as SPRD_WTC_CNT_STEP.
>   - Remove the code which check timeout value at the wrong place.
>   - Add min/max timeout value limit.
>   - Remove set WDOG_HW_RUNNING status at sprd_wdt_enable().
>   - Add timeout/pretimeout judgment when set them.
>   - Support WATCHDOG_NOWAYOUT status.
> 
> Changes since v1:
>   - Use pretimeout instead of own implementation.
>   - Fix timeout loop when loading timeout values.
>   - use the infrastructure to read and set "timeout-sec" property.
>   - Add conditions when start or stop watchdog.
>   - Change the position of enabling watchdog.
>   - Other optimization.
> ---
>   drivers/watchdog/Kconfig    |   8 +
>   drivers/watchdog/Makefile   |   1 +
>   drivers/watchdog/sprd_wdt.c | 415 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 424 insertions(+)
>   create mode 100644 drivers/watchdog/sprd_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index c722cbf..4a77e17 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -787,6 +787,14 @@ config UNIPHIER_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called uniphier_wdt.
>   
> +config SPRD_WATCHDOG
> +	tristate "Spreadtrum watchdog support"
> +	depends on ARCH_SPRD || COMPILE_TEST
> +	select WATCHDOG_CORE
> +	help
> +	  Say Y here to include support watchdog timer embedded
> +	  into the Spreadtrum system.

Maybe better "supported by" instead of "embedded into". Or at least
"embedded in".

> +
>   # AVR32 Architecture
>   
>   config AT32AP700X_WDT
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 56adf9f..187cca2 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -87,6 +87,7 @@ obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
>   obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
>   obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
>   obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
> +obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
>   
>   # AVR32 Architecture
>   obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
> diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
> new file mode 100644
> index 0000000..5fc3dde
> --- /dev/null
> +++ b/drivers/watchdog/sprd_wdt.c
> @@ -0,0 +1,415 @@
> +/*
> + * Spreadtrum watchdog driver
> + * Copyright (C) 2017 Spreadtrum - http://www.spreadtrum.com
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/watchdog.h>
> +
> +#define SPRD_WDT_LOAD_LOW		0x0
> +#define SPRD_WDT_LOAD_HIGH		0x4
> +#define SPRD_WDT_CTRL			0x8
> +#define SPRD_WDT_INT_CLR		0xc
> +#define SPRD_WDT_INT_RAW		0x10
> +#define SPRD_WDT_INT_MSK		0x14
> +#define SPRD_WDT_CNT_LOW		0x18
> +#define SPRD_WDT_CNT_HIGH		0x1c
> +#define SPRD_WDT_LOCK			0x20
> +#define SPRD_WDT_IRQ_LOAD_LOW		0x2c
> +#define SPRD_WDT_IRQ_LOAD_HIGH		0x30
> +
> +/* WDT_CTRL */
> +#define SPRD_WDT_INT_EN_BIT		BIT(0)
> +#define SPRD_WDT_CNT_EN_BIT		BIT(1)
> +#define SPRD_WDT_NEW_VER_EN		BIT(2)
> +#define SPRD_WDT_RST_EN_BIT		BIT(3)
> +
> +/* WDT_INT_CLR */
> +#define SPRD_WDT_INT_CLEAR_BIT		BIT(0)
> +#define SPRD_WDT_RST_CLEAR_BIT		BIT(3)
> +
> +/* WDT_INT_RAW */
> +#define SPRD_WDT_INT_RAW_BIT		BIT(0)
> +#define SPRD_WDT_RST_RAW_BIT		BIT(3)
> +#define SPRD_WDT_LD_BUSY_BIT		BIT(4)
> +
> +/* 1s equale to 32768 counter steps */

equal ?

> +#define SPRD_WDT_CNT_STEP		32768
> +
> +#define SPRD_WDT_UNLOCK_KEY		0xe551
> +#define SPRD_WDT_MIN_TIMROUT		3

TIMROUT ot TIMEOUT ?

> +#define SPRD_WDT_MAX_TIMEOUT		60

Is that really the maximum supported timeout ? Seems a bit low.
Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?

> +
> +#define SPRD_WDT_CNT_HIGH_VALUE		16

Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
it is a shift.

> +#define SPRD_WDT_LOW_VALUE_MASK		GENMASK(15, 0)
> +#define SPRD_WDT_CNT_VALUE_MAX		GENMASK(31, 0)

Does this mask serve a useful purpose ?

> +#define SPRD_WDT_LOAD_TIMEOUT		1000
> +
> +struct sprd_wdt {
> +	void __iomem *base;
> +	struct watchdog_device wdd;
> +	struct clk *enable;
> +	struct clk *rtc_enable;
> +	unsigned int irq;
> +};
> +
> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
> +{
> +	return container_of(wdd, struct sprd_wdt, wdd);
> +}
> +
> +static inline void sprd_wdt_lock(void __iomem *addr)
> +{
> +	writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
> +}
> +
> +static inline void sprd_wdt_unlock(void __iomem *addr)
> +{
> +	writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
> +}
> +
> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> +	return val & SPRD_WDT_NEW_VER_EN;
> +}
> +
> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
> +{
> +	struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
> +
> +	sprd_wdt_unlock(wdt->base);
> +	writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base + SPRD_WDT_INT_CLR);
> +	sprd_wdt_lock(wdt->base);
> +	watchdog_notify_pretimeout(&wdt->wdd);
> +	return IRQ_HANDLED;
> +}
> +
> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
> +		SPRD_WDT_CNT_HIGH_VALUE;
> +	val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
> +		SPRD_WDT_LOW_VALUE_MASK;
> +
> +	return val;
> +}
> +
> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
> +			       u32 pretimeout)
> +{
> +	u32 val, delay_cnt = 0;
> +	u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
> +	u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
> +
> +	sprd_wdt_unlock(wdt->base);
> +	writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
> +		      SPRD_WDT_LOW_VALUE_MASK, wdt->base + SPRD_WDT_LOAD_HIGH);
> +	writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
> +		       wdt->base + SPRD_WDT_LOAD_LOW);
> +	writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
> +			SPRD_WDT_LOW_VALUE_MASK,
> +		       wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
> +	writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
> +		       wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
> +	sprd_wdt_lock(wdt->base);
> +
> +	/*
> +	 * Waiting the load value operation done,
> +	 * it needs two or three RTC clock cycles.
> +	 */
> +	do {
> +		val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
> +		if (!(val & SPRD_WDT_LD_BUSY_BIT))
> +			break;
> +
> +		cpu_relax();
> +	} while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
> +
> +	if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
> +		return -EBUSY;
> +	return 0;
> +}
> +
> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
> +{
> +	u32 val;
> +	int ret;
> +
> +	ret = clk_prepare_enable(wdt->enable);
> +	if (ret)
> +		return ret;
> +	ret = clk_prepare_enable(wdt->rtc_enable);
> +	if (ret)
> +		return ret;
> +
> +	sprd_wdt_unlock(wdt->base);
> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> +	val |= SPRD_WDT_NEW_VER_EN;
> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> +	sprd_wdt_lock(wdt->base);
> +	return 0;
> +}
> +
> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
> +{
> +	sprd_wdt_unlock(wdt->base);
> +	writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
> +	sprd_wdt_lock(wdt->base);
> +
> +	clk_disable_unprepare(wdt->rtc_enable);
> +	clk_disable_unprepare(wdt->enable);
> +}
> +
> +static int sprd_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> +	u32 val;
> +	int ret;
> +
> +	ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
> +	if (ret)
> +		return ret;
> +
> +	sprd_wdt_unlock(wdt->base);
> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> +	val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT | SPRD_WDT_RST_EN_BIT;
> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> +	sprd_wdt_lock(wdt->base);
> +	set_bit(WDOG_HW_RUNNING, &wdd->status);
> +
> +	return 0;
> +}
> +
> +static int sprd_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> +	u32 val;
> +
> +	sprd_wdt_unlock(wdt->base);
> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> +	val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
> +		SPRD_WDT_INT_EN_BIT);
> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> +	sprd_wdt_lock(wdt->base);
> +	return 0;
> +}
> +
> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
> +				u32 timeout)
> +{
> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> +
> +	if (timeout == wdd->timeout)
> +		return 0;
> +
> +	wdd->timeout = timeout;
> +
> +	return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
> +}
> +
> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
> +				   u32 new_pretimeout)
> +{
> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> +
> +	if (new_pretimeout == wdd->pretimeout)
> +		return 0;

This is inconsistent. pretimeout == 0 is accepted until it is set
to a non-zero value once, then 0 is no longer accepted. pretimeout==0
should reflect "pretimeout disabled". If that is not possible you
need to set some non-0 default value in the probe function.

> +	if (new_pretimeout <= wdd->min_timeout)
> +		return -EINVAL;

Why is pretimeout == wdd->min_timeout invalid ?

> +
> +	wdd->pretimeout = new_pretimeout;
> +
> +	return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
> +}
> +
> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> +	u32 val;
> +
> +	val = sprd_wdt_get_cnt_value(wdt);
> +	val = val / SPRD_WDT_CNT_STEP;
> +
> +	return val;
> +}
> +
> +static const struct watchdog_ops sprd_wdt_ops = {
> +	.owner = THIS_MODULE,
> +	.start = sprd_wdt_start,
> +	.stop = sprd_wdt_stop,
> +	.set_timeout = sprd_wdt_set_timeout,
> +	.set_pretimeout = sprd_wdt_set_pretimeout,
> +	.get_timeleft = sprd_wdt_get_timeleft,

Just wondering - no heartbeat function ? Having to load the timer
values for each heartbeat is expensive.

> +};
> +
> +static const struct watchdog_info sprd_wdt_info = {
> +	.options = WDIOF_SETTIMEOUT |
> +		   WDIOF_PRETIMEOUT |
> +		   WDIOF_MAGICCLOSE |
> +		   WDIOF_KEEPALIVEPING,
> +	.identity = "Spreadtrum Watchdog Timer",
> +};
> +
> +static int sprd_wdt_probe(struct platform_device *pdev)
> +{
> +	struct resource *wdt_res;
> +	struct sprd_wdt *wdt;
> +	int ret;
> +
> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!wdt_res) {
> +		dev_err(&pdev->dev, "failed to memory resource\n");
> +		return -ENOMEM;
> +	}

Unnecessary error check and message. devm_ioremap_resource()
returns an error if res is NULL.

> +
> +	wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
> +	if (IS_ERR(wdt->base))

Move the error message to here.

> +		return PTR_ERR(wdt->base);
> +
> +	wdt->enable = devm_clk_get(&pdev->dev, "enable");
> +	if (IS_ERR(wdt->enable)) {
> +		dev_err(&pdev->dev, "can't get the enable clock\n");
> +		return PTR_ERR(wdt->enable);
> +	}
> +
> +	wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
> +	if (IS_ERR(wdt->rtc_enable)) {
> +		dev_err(&pdev->dev, "can't get the rtc enable clock\n");
> +		return PTR_ERR(wdt->rtc_enable);
> +	}
> +
> +	wdt->irq = platform_get_irq(pdev, 0);
> +	if (wdt->irq < 0) {
> +		dev_err(&pdev->dev, "failed to get IRQ resource\n");
> +		return wdt->irq;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
> +			       IRQF_NO_SUSPEND, "sprd-wdt", (void *)wdt);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to register irq\n");
> +		return ret;
> +	}
> +
> +	wdt->wdd.info = &sprd_wdt_info;
> +	wdt->wdd.ops = &sprd_wdt_ops;
> +	wdt->wdd.parent = &pdev->dev;
> +	wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
> +	wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
> +
You might want to set wdt->wdd.timeout to a default value.

> +	ret = sprd_wdt_enable(wdt);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to enable wdt\n");
> +		return ret;
> +	}
> +

This needs a matching sprd_wdt_disable() call in the remove function.
Best way to handle this would be to add devm_add_action() here.

> +	watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
> +	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
> +
> +	ret = watchdog_register_device(&wdt->wdd);

Unfortunately this doesn't work. It leaves interrupts enabled
after the watchdog device is removed in sprd_wdt_remove(),
but the driver will be gone. I would suggest to use
devm_watchdog_register_device() and reorder calls to request
the interrupt after registering the watchdog device. Then you
can drop the remove function entirely.

> +	if (ret) {
> +		sprd_wdt_disable(wdt);
> +		dev_err(&pdev->dev, "failed to register watchdog\n");
> +		return ret;
> +	}
> +	platform_set_drvdata(pdev, wdt);
> +
> +	return 0;
> +}
> +
> +static int sprd_wdt_remove(struct platform_device *pdev)
> +{
> +	struct sprd_wdt *wdt = platform_get_drvdata(pdev);
> +
> +	watchdog_unregister_device(&wdt->wdd);
> +
> +	if (sprd_wdt_is_running(wdt))
> +		dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
> +	return 0;
> +}
> +
> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
> +{
> +	struct watchdog_device *wdd = dev_get_drvdata(dev);
> +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> +
> +	if (watchdog_active(wdd)) {
> +		sprd_wdt_stop(&wdt->wdd);
> +		sprd_wdt_disable(wdt);

Are you sure you only want to disable the clocks if the watchdog was active ?
That seems to be a bit inconsistent.

> +	}
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
> +{
> +	struct watchdog_device *wdd = dev_get_drvdata(dev);
> +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> +	int ret;
> +
> +	if (watchdog_active(wdd)) {
> +		ret = sprd_wdt_enable(wdt);
> +		if (ret)
> +			return ret;
> +		ret = sprd_wdt_start(&wdt->wdd);
> +		if (ret) {
> +			sprd_wdt_disable(wdt);
> +			return ret;
> +		}

This can leave the system in an inconsistent state. Sometimes the wdt may be
disabled, sometimes not.

> +	}
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops sprd_wdt_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(sprd_wdt_pm_suspend,
> +				sprd_wdt_pm_resume)
> +};
> +
> +static const struct of_device_id sprd_wdt_match_table[] = {
> +	{ .compatible = "sprd,sp9860-wdt", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, sprd_wdt_match_table);
> +
> +static struct platform_driver sprd_watchdog_driver = {
> +	.probe	= sprd_wdt_probe,
> +	.remove	= sprd_wdt_remove,
> +	.driver	= {
> +		.name = "sprd-wdt",
> +		.of_match_table = sprd_wdt_match_table,
> +		.pm = &sprd_wdt_pm_ops,
> +	},
> +};
> +module_platform_driver(sprd_watchdog_driver);
> +
> +MODULE_AUTHOR("Eric Long <eric.long@spreadtrum.com>");
> +MODULE_DESCRIPTION("Spreadtrum Watchdog Timer Controller Driver");
> +MODULE_LICENSE("GPL v2");
> 

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Hi Guenter,

Thanks for you commonts.

On Thu, Oct 26, 2017 at 10:23:40PM -0700, Guenter Roeck wrote:
> On 10/26/2017 07:28 PM, Eric Long wrote:
> >This patch adds the watchdog driver for Spreadtrum SC9860 platform.
> >
> >Signed-off-by: Eric Long <eric.long@spreadtrum.com>
> >---
> >Change since v2:
> >  - Rename all the macors, add SPRD tag at the head of the macro names.
> >  - Rename SPRD_WDT_CLK as SPRD_WTC_CNT_STEP.
> >  - Remove the code which check timeout value at the wrong place.
> >  - Add min/max timeout value limit.
> >  - Remove set WDOG_HW_RUNNING status at sprd_wdt_enable().
> >  - Add timeout/pretimeout judgment when set them.
> >  - Support WATCHDOG_NOWAYOUT status.
> >
> >Changes since v1:
> >  - Use pretimeout instead of own implementation.
> >  - Fix timeout loop when loading timeout values.
> >  - use the infrastructure to read and set "timeout-sec" property.
> >  - Add conditions when start or stop watchdog.
> >  - Change the position of enabling watchdog.
> >  - Other optimization.
> >---
> >  drivers/watchdog/Kconfig    |   8 +
> >  drivers/watchdog/Makefile   |   1 +
> >  drivers/watchdog/sprd_wdt.c | 415 ++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 424 insertions(+)
> >  create mode 100644 drivers/watchdog/sprd_wdt.c
> >
> >diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> >index c722cbf..4a77e17 100644
> >--- a/drivers/watchdog/Kconfig
> >+++ b/drivers/watchdog/Kconfig
> >@@ -787,6 +787,14 @@ config UNIPHIER_WATCHDOG
> >  	  To compile this driver as a module, choose M here: the
> >  	  module will be called uniphier_wdt.
> >+config SPRD_WATCHDOG
> >+	tristate "Spreadtrum watchdog support"
> >+	depends on ARCH_SPRD || COMPILE_TEST
> >+	select WATCHDOG_CORE
> >+	help
> >+	  Say Y here to include support watchdog timer embedded
> >+	  into the Spreadtrum system.
> 
> Maybe better "supported by" instead of "embedded into". Or at least
> "embedded in".

OK, I will fix it.
 
> >+
> >  # AVR32 Architecture
> >  config AT32AP700X_WDT
> >diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> >index 56adf9f..187cca2 100644
> >--- a/drivers/watchdog/Makefile
> >+++ b/drivers/watchdog/Makefile
> >@@ -87,6 +87,7 @@ obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
> >  obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
> >  obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
> >  obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
> >+obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
> >  # AVR32 Architecture
> >  obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
> >diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
> >new file mode 100644
> >index 0000000..5fc3dde
> >--- /dev/null
> >+++ b/drivers/watchdog/sprd_wdt.c
> >@@ -0,0 +1,415 @@
> >+/*
> >+ * Spreadtrum watchdog driver
> >+ * Copyright (C) 2017 Spreadtrum - http://www.spreadtrum.com
> >+ *
> >+ * This program is free software; you can redistribute it and/or
> >+ * modify it under the terms of the GNU General Public License
> >+ * version 2 as published by the Free Software Foundation.
> >+ *
> >+ * This program is distributed in the hope that it will be useful, but
> >+ * WITHOUT ANY WARRANTY; without even the implied warranty of
> >+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> >+ * General Public License for more details.
> >+ */
> >+
> >+#include <linux/bitops.h>
> >+#include <linux/clk.h>
> >+#include <linux/err.h>
> >+#include <linux/interrupt.h>
> >+#include <linux/io.h>
> >+#include <linux/kernel.h>
> >+#include <linux/module.h>
> >+#include <linux/of.h>
> >+#include <linux/of_address.h>
> >+#include <linux/platform_device.h>
> >+#include <linux/watchdog.h>
> >+
> >+#define SPRD_WDT_LOAD_LOW		0x0
> >+#define SPRD_WDT_LOAD_HIGH		0x4
> >+#define SPRD_WDT_CTRL			0x8
> >+#define SPRD_WDT_INT_CLR		0xc
> >+#define SPRD_WDT_INT_RAW		0x10
> >+#define SPRD_WDT_INT_MSK		0x14
> >+#define SPRD_WDT_CNT_LOW		0x18
> >+#define SPRD_WDT_CNT_HIGH		0x1c
> >+#define SPRD_WDT_LOCK			0x20
> >+#define SPRD_WDT_IRQ_LOAD_LOW		0x2c
> >+#define SPRD_WDT_IRQ_LOAD_HIGH		0x30
> >+
> >+/* WDT_CTRL */
> >+#define SPRD_WDT_INT_EN_BIT		BIT(0)
> >+#define SPRD_WDT_CNT_EN_BIT		BIT(1)
> >+#define SPRD_WDT_NEW_VER_EN		BIT(2)
> >+#define SPRD_WDT_RST_EN_BIT		BIT(3)
> >+
> >+/* WDT_INT_CLR */
> >+#define SPRD_WDT_INT_CLEAR_BIT		BIT(0)
> >+#define SPRD_WDT_RST_CLEAR_BIT		BIT(3)
> >+
> >+/* WDT_INT_RAW */
> >+#define SPRD_WDT_INT_RAW_BIT		BIT(0)
> >+#define SPRD_WDT_RST_RAW_BIT		BIT(3)
> >+#define SPRD_WDT_LD_BUSY_BIT		BIT(4)
> >+
> >+/* 1s equale to 32768 counter steps */
> 
> equal ?
>

OK, I will fix it.

> >+#define SPRD_WDT_CNT_STEP		32768
> >+
> >+#define SPRD_WDT_UNLOCK_KEY		0xe551
> >+#define SPRD_WDT_MIN_TIMROUT		3
> 
> TIMROUT ot TIMEOUT ?
> 

OK, I will fix it.

> >+#define SPRD_WDT_MAX_TIMEOUT		60
> 
> Is that really the maximum supported timeout ? Seems a bit low.
> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
> 

It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
but it doesn't unnecessary to support so big value, if the system can not
response it in 60s, the watchdog could trigger timeout.

> >+
> >+#define SPRD_WDT_CNT_HIGH_VALUE		16
> 
> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
> it is a shift.
>

Yes, you are right, _SHIFT will be better.
 
> >+#define SPRD_WDT_LOW_VALUE_MASK		GENMASK(15, 0)
> >+#define SPRD_WDT_CNT_VALUE_MAX		GENMASK(31, 0)
> 
> Does this mask serve a useful purpose ?
> 

OK, I will remove it, thanks!

> >+#define SPRD_WDT_LOAD_TIMEOUT		1000
> >+
> >+struct sprd_wdt {
> >+	void __iomem *base;
> >+	struct watchdog_device wdd;
> >+	struct clk *enable;
> >+	struct clk *rtc_enable;
> >+	unsigned int irq;
> >+};
> >+
> >+static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
> >+{
> >+	return container_of(wdd, struct sprd_wdt, wdd);
> >+}
> >+
> >+static inline void sprd_wdt_lock(void __iomem *addr)
> >+{
> >+	writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
> >+}
> >+
> >+static inline void sprd_wdt_unlock(void __iomem *addr)
> >+{
> >+	writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
> >+}
> >+
> >+static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
> >+{
> >+	u32 val;
> >+
> >+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> >+	return val & SPRD_WDT_NEW_VER_EN;
> >+}
> >+
> >+static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
> >+{
> >+	struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
> >+
> >+	sprd_wdt_unlock(wdt->base);
> >+	writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base + SPRD_WDT_INT_CLR);
> >+	sprd_wdt_lock(wdt->base);
> >+	watchdog_notify_pretimeout(&wdt->wdd);
> >+	return IRQ_HANDLED;
> >+}
> >+
> >+static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
> >+{
> >+	u32 val;
> >+
> >+	val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
> >+		SPRD_WDT_CNT_HIGH_VALUE;
> >+	val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
> >+		SPRD_WDT_LOW_VALUE_MASK;
> >+
> >+	return val;
> >+}
> >+
> >+static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
> >+			       u32 pretimeout)
> >+{
> >+	u32 val, delay_cnt = 0;
> >+	u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
> >+	u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
> >+
> >+	sprd_wdt_unlock(wdt->base);
> >+	writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
> >+		      SPRD_WDT_LOW_VALUE_MASK, wdt->base + SPRD_WDT_LOAD_HIGH);
> >+	writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
> >+		       wdt->base + SPRD_WDT_LOAD_LOW);
> >+	writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
> >+			SPRD_WDT_LOW_VALUE_MASK,
> >+		       wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
> >+	writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
> >+		       wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
> >+	sprd_wdt_lock(wdt->base);
> >+
> >+	/*
> >+	 * Waiting the load value operation done,
> >+	 * it needs two or three RTC clock cycles.
> >+	 */
> >+	do {
> >+		val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
> >+		if (!(val & SPRD_WDT_LD_BUSY_BIT))
> >+			break;
> >+
> >+		cpu_relax();
> >+	} while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
> >+
> >+	if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
> >+		return -EBUSY;
> >+	return 0;
> >+}
> >+
> >+static int sprd_wdt_enable(struct sprd_wdt *wdt)
> >+{
> >+	u32 val;
> >+	int ret;
> >+
> >+	ret = clk_prepare_enable(wdt->enable);
> >+	if (ret)
> >+		return ret;
> >+	ret = clk_prepare_enable(wdt->rtc_enable);
> >+	if (ret)
> >+		return ret;
> >+
> >+	sprd_wdt_unlock(wdt->base);
> >+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> >+	val |= SPRD_WDT_NEW_VER_EN;
> >+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> >+	sprd_wdt_lock(wdt->base);
> >+	return 0;
> >+}
> >+
> >+static void sprd_wdt_disable(struct sprd_wdt *wdt)
> >+{
> >+	sprd_wdt_unlock(wdt->base);
> >+	writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
> >+	sprd_wdt_lock(wdt->base);
> >+
> >+	clk_disable_unprepare(wdt->rtc_enable);
> >+	clk_disable_unprepare(wdt->enable);
> >+}
> >+
> >+static int sprd_wdt_start(struct watchdog_device *wdd)
> >+{
> >+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> >+	u32 val;
> >+	int ret;
> >+
> >+	ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
> >+	if (ret)
> >+		return ret;
> >+
> >+	sprd_wdt_unlock(wdt->base);
> >+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> >+	val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT | SPRD_WDT_RST_EN_BIT;
> >+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> >+	sprd_wdt_lock(wdt->base);
> >+	set_bit(WDOG_HW_RUNNING, &wdd->status);
> >+
> >+	return 0;
> >+}
> >+
> >+static int sprd_wdt_stop(struct watchdog_device *wdd)
> >+{
> >+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> >+	u32 val;
> >+
> >+	sprd_wdt_unlock(wdt->base);
> >+	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
> >+	val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
> >+		SPRD_WDT_INT_EN_BIT);
> >+	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
> >+	sprd_wdt_lock(wdt->base);
> >+	return 0;
> >+}
> >+
> >+static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
> >+				u32 timeout)
> >+{
> >+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> >+
> >+	if (timeout == wdd->timeout)
> >+		return 0;
> >+
> >+	wdd->timeout = timeout;
> >+
> >+	return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
> >+}
> >+
> >+static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
> >+				   u32 new_pretimeout)
> >+{
> >+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> >+
> >+	if (new_pretimeout == wdd->pretimeout)
> >+		return 0;
> 
> This is inconsistent. pretimeout == 0 is accepted until it is set
> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
> should reflect "pretimeout disabled". If that is not possible you
> need to set some non-0 default value in the probe function.
>

I understand your opinion, I will fix it.

> >+	if (new_pretimeout <= wdd->min_timeout)
> >+		return -EINVAL;
> 
> Why is pretimeout == wdd->min_timeout invalid ?
> 

OK, you are right, it should be pretimeout < min_timeout.

> >+
> >+	wdd->pretimeout = new_pretimeout;
> >+
> >+	return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
> >+}
> >+
> >+static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
> >+{
> >+	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
> >+	u32 val;
> >+
> >+	val = sprd_wdt_get_cnt_value(wdt);
> >+	val = val / SPRD_WDT_CNT_STEP;
> >+
> >+	return val;
> >+}
> >+
> >+static const struct watchdog_ops sprd_wdt_ops = {
> >+	.owner = THIS_MODULE,
> >+	.start = sprd_wdt_start,
> >+	.stop = sprd_wdt_stop,
> >+	.set_timeout = sprd_wdt_set_timeout,
> >+	.set_pretimeout = sprd_wdt_set_pretimeout,
> >+	.get_timeleft = sprd_wdt_get_timeleft,
> 
> Just wondering - no heartbeat function ? Having to load the timer
> values for each heartbeat is expensive.
>

Unfortunately, this watchdog has not RELOAD register.
 
> >+};
> >+
> >+static const struct watchdog_info sprd_wdt_info = {
> >+	.options = WDIOF_SETTIMEOUT |
> >+		   WDIOF_PRETIMEOUT |
> >+		   WDIOF_MAGICCLOSE |
> >+		   WDIOF_KEEPALIVEPING,
> >+	.identity = "Spreadtrum Watchdog Timer",
> >+};
> >+
> >+static int sprd_wdt_probe(struct platform_device *pdev)
> >+{
> >+	struct resource *wdt_res;
> >+	struct sprd_wdt *wdt;
> >+	int ret;
> >+
> >+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> >+	if (!wdt)
> >+		return -ENOMEM;
> >+
> >+	wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >+	if (!wdt_res) {
> >+		dev_err(&pdev->dev, "failed to memory resource\n");
> >+		return -ENOMEM;
> >+	}
> 
> Unnecessary error check and message. devm_ioremap_resource()
> returns an error if res is NULL.
>

OK, I will fix it.
 
> >+
> >+	wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
> >+	if (IS_ERR(wdt->base))
> 
> Move the error message to here.
> 
> >+		return PTR_ERR(wdt->base);
> >+
> >+	wdt->enable = devm_clk_get(&pdev->dev, "enable");
> >+	if (IS_ERR(wdt->enable)) {
> >+		dev_err(&pdev->dev, "can't get the enable clock\n");
> >+		return PTR_ERR(wdt->enable);
> >+	}
> >+
> >+	wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
> >+	if (IS_ERR(wdt->rtc_enable)) {
> >+		dev_err(&pdev->dev, "can't get the rtc enable clock\n");
> >+		return PTR_ERR(wdt->rtc_enable);
> >+	}
> >+
> >+	wdt->irq = platform_get_irq(pdev, 0);
> >+	if (wdt->irq < 0) {
> >+		dev_err(&pdev->dev, "failed to get IRQ resource\n");
> >+		return wdt->irq;
> >+	}
> >+
> >+	ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
> >+			       IRQF_NO_SUSPEND, "sprd-wdt", (void *)wdt);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "failed to register irq\n");
> >+		return ret;
> >+	}
> >+
> >+	wdt->wdd.info = &sprd_wdt_info;
> >+	wdt->wdd.ops = &sprd_wdt_ops;
> >+	wdt->wdd.parent = &pdev->dev;
> >+	wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
> >+	wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
> >+
> You might want to set wdt->wdd.timeout to a default value.
>

OK, I will set a default timeout value in case of no timeout-sec in device-tree.
 
> >+	ret = sprd_wdt_enable(wdt);
> >+	if (ret) {
> >+		dev_err(&pdev->dev, "failed to enable wdt\n");
> >+		return ret;
> >+	}
> >+
> 
> This needs a matching sprd_wdt_disable() call in the remove function.
> Best way to handle this would be to add devm_add_action() here.
> 

If add devm_add_action(), it will be called in the remove function,
but this is not our expect, if someone remove this module, we want it just timeout.

> >+	watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
> >+	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
> >+
> >+	ret = watchdog_register_device(&wdt->wdd);
> 
> Unfortunately this doesn't work. It leaves interrupts enabled
> after the watchdog device is removed in sprd_wdt_remove(),
> but the driver will be gone. I would suggest to use
> devm_watchdog_register_device() and reorder calls to request
> the interrupt after registering the watchdog device. Then you
> can drop the remove function entirely.
> 

Yes, you are right, I understand your opinion, and it is very important,
devm_watchdog_register_device() is better. Thanks.

> >+	if (ret) {
> >+		sprd_wdt_disable(wdt);
> >+		dev_err(&pdev->dev, "failed to register watchdog\n");
> >+		return ret;
> >+	}
> >+	platform_set_drvdata(pdev, wdt);
> >+
> >+	return 0;
> >+}
> >+
> >+static int sprd_wdt_remove(struct platform_device *pdev)
> >+{
> >+	struct sprd_wdt *wdt = platform_get_drvdata(pdev);
> >+
> >+	watchdog_unregister_device(&wdt->wdd);
> >+
> >+	if (sprd_wdt_is_running(wdt))
> >+		dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
> >+	return 0;
> >+}
> >+
> >+static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
> >+{
> >+	struct watchdog_device *wdd = dev_get_drvdata(dev);
> >+	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> >+
> >+	if (watchdog_active(wdd)) {
> >+		sprd_wdt_stop(&wdt->wdd);
> >+		sprd_wdt_disable(wdt);
> 
> Are you sure you only want to disable the clocks if the watchdog was active ?
> That seems to be a bit inconsistent.
> 

This watchdog is in always on power domain, if system suspend, it needs to
disable it, or it will timeout.

> >+	}
> >+
> >+	return 0;
> >+}
> >+
> >+static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
> >+{
> >+	struct watchdog_device *wdd = dev_get_drvdata(dev);
> >+	struct sprd_wdt *wdt = dev_get_drvdata(dev);
> >+	int ret;
> >+
> >+	if (watchdog_active(wdd)) {
> >+		ret = sprd_wdt_enable(wdt);
> >+		if (ret)
> >+			return ret;
> >+		ret = sprd_wdt_start(&wdt->wdd);
> >+		if (ret) {
> >+			sprd_wdt_disable(wdt);
> >+			return ret;
> >+		}
> 
> This can leave the system in an inconsistent state. Sometimes the wdt may be
> disabled, sometimes not.
>

If watchdog enable failed, it means there is something wrong in this system.
 
> >+	}
> >+
> >+	return 0;
> >+}
> >+
> >+static const struct dev_pm_ops sprd_wdt_pm_ops = {
> >+	SET_SYSTEM_SLEEP_PM_OPS(sprd_wdt_pm_suspend,
> >+				sprd_wdt_pm_resume)
> >+};
> >+
> >+static const struct of_device_id sprd_wdt_match_table[] = {
> >+	{ .compatible = "sprd,sp9860-wdt", },
> >+	{},
> >+};
> >+MODULE_DEVICE_TABLE(of, sprd_wdt_match_table);
> >+
> >+static struct platform_driver sprd_watchdog_driver = {
> >+	.probe	= sprd_wdt_probe,
> >+	.remove	= sprd_wdt_remove,
> >+	.driver	= {
> >+		.name = "sprd-wdt",
> >+		.of_match_table = sprd_wdt_match_table,
> >+		.pm = &sprd_wdt_pm_ops,
> >+	},
> >+};
> >+module_platform_driver(sprd_watchdog_driver);
> >+
> >+MODULE_AUTHOR("Eric Long <eric.long@spreadtrum.com>");
> >+MODULE_DESCRIPTION("Spreadtrum Watchdog Timer Controller Driver");
> >+MODULE_LICENSE("GPL v2");
> >
> 
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On 10/27/2017 12:54 AM, Eric Long wrote:
> Hi Guenter,
> 
> Thanks for you commonts.
> 
> On Thu, Oct 26, 2017 at 10:23:40PM -0700, Guenter Roeck wrote:
>> On 10/26/2017 07:28 PM, Eric Long wrote:
>>> This patch adds the watchdog driver for Spreadtrum SC9860 platform.
>>>
>>> Signed-off-by: Eric Long <eric.long@spreadtrum.com>
>>> ---
>>> Change since v2:
>>>   - Rename all the macors, add SPRD tag at the head of the macro names.
>>>   - Rename SPRD_WDT_CLK as SPRD_WTC_CNT_STEP.
>>>   - Remove the code which check timeout value at the wrong place.
>>>   - Add min/max timeout value limit.
>>>   - Remove set WDOG_HW_RUNNING status at sprd_wdt_enable().
>>>   - Add timeout/pretimeout judgment when set them.
>>>   - Support WATCHDOG_NOWAYOUT status.
>>>
>>> Changes since v1:
>>>   - Use pretimeout instead of own implementation.
>>>   - Fix timeout loop when loading timeout values.
>>>   - use the infrastructure to read and set "timeout-sec" property.
>>>   - Add conditions when start or stop watchdog.
>>>   - Change the position of enabling watchdog.
>>>   - Other optimization.
>>> ---
>>>   drivers/watchdog/Kconfig    |   8 +
>>>   drivers/watchdog/Makefile   |   1 +
>>>   drivers/watchdog/sprd_wdt.c | 415 ++++++++++++++++++++++++++++++++++++++++++++
>>>   3 files changed, 424 insertions(+)
>>>   create mode 100644 drivers/watchdog/sprd_wdt.c
>>>
>>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
>>> index c722cbf..4a77e17 100644
>>> --- a/drivers/watchdog/Kconfig
>>> +++ b/drivers/watchdog/Kconfig
>>> @@ -787,6 +787,14 @@ config UNIPHIER_WATCHDOG
>>>   	  To compile this driver as a module, choose M here: the
>>>   	  module will be called uniphier_wdt.
>>> +config SPRD_WATCHDOG
>>> +	tristate "Spreadtrum watchdog support"
>>> +	depends on ARCH_SPRD || COMPILE_TEST
>>> +	select WATCHDOG_CORE
>>> +	help
>>> +	  Say Y here to include support watchdog timer embedded
>>> +	  into the Spreadtrum system.
>>
>> Maybe better "supported by" instead of "embedded into". Or at least
>> "embedded in".
> 
> OK, I will fix it.
>   
>>> +
>>>   # AVR32 Architecture
>>>   config AT32AP700X_WDT
>>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
>>> index 56adf9f..187cca2 100644
>>> --- a/drivers/watchdog/Makefile
>>> +++ b/drivers/watchdog/Makefile
>>> @@ -87,6 +87,7 @@ obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
>>>   obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
>>>   obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
>>>   obj-$(CONFIG_UNIPHIER_WATCHDOG) += uniphier_wdt.o
>>> +obj-$(CONFIG_SPRD_WATCHDOG) += sprd_wdt.o
>>>   # AVR32 Architecture
>>>   obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
>>> diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
>>> new file mode 100644
>>> index 0000000..5fc3dde
>>> --- /dev/null
>>> +++ b/drivers/watchdog/sprd_wdt.c
>>> @@ -0,0 +1,415 @@
>>> +/*
>>> + * Spreadtrum watchdog driver
>>> + * Copyright (C) 2017 Spreadtrum - http://www.spreadtrum.com
>>> + *
>>> + * This program is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU General Public License
>>> + * version 2 as published by the Free Software Foundation.
>>> + *
>>> + * This program is distributed in the hope that it will be useful, but
>>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * General Public License for more details.
>>> + */
>>> +
>>> +#include <linux/bitops.h>
>>> +#include <linux/clk.h>
>>> +#include <linux/err.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/io.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_address.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/watchdog.h>
>>> +
>>> +#define SPRD_WDT_LOAD_LOW		0x0
>>> +#define SPRD_WDT_LOAD_HIGH		0x4
>>> +#define SPRD_WDT_CTRL			0x8
>>> +#define SPRD_WDT_INT_CLR		0xc
>>> +#define SPRD_WDT_INT_RAW		0x10
>>> +#define SPRD_WDT_INT_MSK		0x14
>>> +#define SPRD_WDT_CNT_LOW		0x18
>>> +#define SPRD_WDT_CNT_HIGH		0x1c
>>> +#define SPRD_WDT_LOCK			0x20
>>> +#define SPRD_WDT_IRQ_LOAD_LOW		0x2c
>>> +#define SPRD_WDT_IRQ_LOAD_HIGH		0x30
>>> +
>>> +/* WDT_CTRL */
>>> +#define SPRD_WDT_INT_EN_BIT		BIT(0)
>>> +#define SPRD_WDT_CNT_EN_BIT		BIT(1)
>>> +#define SPRD_WDT_NEW_VER_EN		BIT(2)
>>> +#define SPRD_WDT_RST_EN_BIT		BIT(3)
>>> +
>>> +/* WDT_INT_CLR */
>>> +#define SPRD_WDT_INT_CLEAR_BIT		BIT(0)
>>> +#define SPRD_WDT_RST_CLEAR_BIT		BIT(3)
>>> +
>>> +/* WDT_INT_RAW */
>>> +#define SPRD_WDT_INT_RAW_BIT		BIT(0)
>>> +#define SPRD_WDT_RST_RAW_BIT		BIT(3)
>>> +#define SPRD_WDT_LD_BUSY_BIT		BIT(4)
>>> +
>>> +/* 1s equale to 32768 counter steps */
>>
>> equal ?
>>
> 
> OK, I will fix it.
> 
>>> +#define SPRD_WDT_CNT_STEP		32768
>>> +
>>> +#define SPRD_WDT_UNLOCK_KEY		0xe551
>>> +#define SPRD_WDT_MIN_TIMROUT		3
>>
>> TIMROUT ot TIMEOUT ?
>>
> 
> OK, I will fix it.
> 
>>> +#define SPRD_WDT_MAX_TIMEOUT		60
>>
>> Is that really the maximum supported timeout ? Seems a bit low.
>> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
>>
> 
> It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
> but it doesn't unnecessary to support so big value, if the system can not
> response it in 60s, the watchdog could trigger timeout.
> 
It is customary to provide the highest possible value here.
No one is forced to set such high values. You are making a choice for
others here. But, sure, if you insist; not worth arguing about.

>>> +
>>> +#define SPRD_WDT_CNT_HIGH_VALUE		16
>>
>> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
>> it is a shift.
>>
> 
> Yes, you are right, _SHIFT will be better.
>   
>>> +#define SPRD_WDT_LOW_VALUE_MASK		GENMASK(15, 0)
>>> +#define SPRD_WDT_CNT_VALUE_MAX		GENMASK(31, 0)
>>
>> Does this mask serve a useful purpose ?
>>
> 
> OK, I will remove it, thanks!
> 
>>> +#define SPRD_WDT_LOAD_TIMEOUT		1000
>>> +
>>> +struct sprd_wdt {
>>> +	void __iomem *base;
>>> +	struct watchdog_device wdd;
>>> +	struct clk *enable;
>>> +	struct clk *rtc_enable;
>>> +	unsigned int irq;
>>> +};
>>> +
>>> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
>>> +{
>>> +	return container_of(wdd, struct sprd_wdt, wdd);
>>> +}
>>> +
>>> +static inline void sprd_wdt_lock(void __iomem *addr)
>>> +{
>>> +	writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
>>> +}
>>> +
>>> +static inline void sprd_wdt_unlock(void __iomem *addr)
>>> +{
>>> +	writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
>>> +}
>>> +
>>> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
>>> +{
>>> +	u32 val;
>>> +
>>> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>> +	return val & SPRD_WDT_NEW_VER_EN;
>>> +}
>>> +
>>> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
>>> +{
>>> +	struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
>>> +
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base + SPRD_WDT_INT_CLR);
>>> +	sprd_wdt_lock(wdt->base);
>>> +	watchdog_notify_pretimeout(&wdt->wdd);
>>> +	return IRQ_HANDLED;
>>> +}
>>> +
>>> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
>>> +{
>>> +	u32 val;
>>> +
>>> +	val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
>>> +		SPRD_WDT_CNT_HIGH_VALUE;
>>> +	val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
>>> +		SPRD_WDT_LOW_VALUE_MASK;
>>> +
>>> +	return val;
>>> +}
>>> +
>>> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
>>> +			       u32 pretimeout)
>>> +{
>>> +	u32 val, delay_cnt = 0;
>>> +	u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
>>> +	u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>>> +
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>> +		      SPRD_WDT_LOW_VALUE_MASK, wdt->base + SPRD_WDT_LOAD_HIGH);
>>> +	writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
>>> +		       wdt->base + SPRD_WDT_LOAD_LOW);
>>> +	writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>> +			SPRD_WDT_LOW_VALUE_MASK,
>>> +		       wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
>>> +	writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
>>> +		       wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
>>> +	sprd_wdt_lock(wdt->base);
>>> +
>>> +	/*
>>> +	 * Waiting the load value operation done,
>>> +	 * it needs two or three RTC clock cycles.
>>> +	 */
>>> +	do {
>>> +		val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
>>> +		if (!(val & SPRD_WDT_LD_BUSY_BIT))
>>> +			break;
>>> +
>>> +		cpu_relax();
>>> +	} while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>>> +
>>> +	if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>>> +		return -EBUSY;
>>> +	return 0;
>>> +}
>>> +
>>> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
>>> +{
>>> +	u32 val;
>>> +	int ret;
>>> +
>>> +	ret = clk_prepare_enable(wdt->enable);
>>> +	if (ret)
>>> +		return ret;
>>> +	ret = clk_prepare_enable(wdt->rtc_enable);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>> +	val |= SPRD_WDT_NEW_VER_EN;
>>> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>> +	sprd_wdt_lock(wdt->base);
>>> +	return 0;
>>> +}
>>> +
>>> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
>>> +{
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
>>> +	sprd_wdt_lock(wdt->base);
>>> +
>>> +	clk_disable_unprepare(wdt->rtc_enable);
>>> +	clk_disable_unprepare(wdt->enable);
>>> +}
>>> +
>>> +static int sprd_wdt_start(struct watchdog_device *wdd)
>>> +{
>>> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>> +	u32 val;
>>> +	int ret;
>>> +
>>> +	ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>> +	val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT | SPRD_WDT_RST_EN_BIT;
>>> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>> +	sprd_wdt_lock(wdt->base);
>>> +	set_bit(WDOG_HW_RUNNING, &wdd->status);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int sprd_wdt_stop(struct watchdog_device *wdd)
>>> +{
>>> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>> +	u32 val;
>>> +
>>> +	sprd_wdt_unlock(wdt->base);
>>> +	val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>> +	val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
>>> +		SPRD_WDT_INT_EN_BIT);
>>> +	writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>> +	sprd_wdt_lock(wdt->base);
>>> +	return 0;
>>> +}
>>> +
>>> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
>>> +				u32 timeout)
>>> +{
>>> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>> +
>>> +	if (timeout == wdd->timeout)
>>> +		return 0;
>>> +
>>> +	wdd->timeout = timeout;
>>> +
>>> +	return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
>>> +}
>>> +
>>> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
>>> +				   u32 new_pretimeout)
>>> +{
>>> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>> +
>>> +	if (new_pretimeout == wdd->pretimeout)
>>> +		return 0;
>>
>> This is inconsistent. pretimeout == 0 is accepted until it is set
>> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
>> should reflect "pretimeout disabled". If that is not possible you
>> need to set some non-0 default value in the probe function.
>>
> 
> I understand your opinion, I will fix it.
> 
>>> +	if (new_pretimeout <= wdd->min_timeout)
>>> +		return -EINVAL;
>>
>> Why is pretimeout == wdd->min_timeout invalid ?
>>
> 
> OK, you are right, it should be pretimeout < min_timeout.
> 
>>> +
>>> +	wdd->pretimeout = new_pretimeout;
>>> +
>>> +	return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
>>> +}
>>> +
>>> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
>>> +{
>>> +	struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>> +	u32 val;
>>> +
>>> +	val = sprd_wdt_get_cnt_value(wdt);
>>> +	val = val / SPRD_WDT_CNT_STEP;
>>> +
>>> +	return val;
>>> +}
>>> +
>>> +static const struct watchdog_ops sprd_wdt_ops = {
>>> +	.owner = THIS_MODULE,
>>> +	.start = sprd_wdt_start,
>>> +	.stop = sprd_wdt_stop,
>>> +	.set_timeout = sprd_wdt_set_timeout,
>>> +	.set_pretimeout = sprd_wdt_set_pretimeout,
>>> +	.get_timeleft = sprd_wdt_get_timeleft,
>>
>> Just wondering - no heartbeat function ? Having to load the timer
>> values for each heartbeat is expensive.
>>
> 
> Unfortunately, this watchdog has not RELOAD register.
>   
>>> +};
>>> +
>>> +static const struct watchdog_info sprd_wdt_info = {
>>> +	.options = WDIOF_SETTIMEOUT |
>>> +		   WDIOF_PRETIMEOUT |
>>> +		   WDIOF_MAGICCLOSE |
>>> +		   WDIOF_KEEPALIVEPING,
>>> +	.identity = "Spreadtrum Watchdog Timer",
>>> +};
>>> +
>>> +static int sprd_wdt_probe(struct platform_device *pdev)
>>> +{
>>> +	struct resource *wdt_res;
>>> +	struct sprd_wdt *wdt;
>>> +	int ret;
>>> +
>>> +	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>> +	if (!wdt)
>>> +		return -ENOMEM;
>>> +
>>> +	wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> +	if (!wdt_res) {
>>> +		dev_err(&pdev->dev, "failed to memory resource\n");
>>> +		return -ENOMEM;
>>> +	}
>>
>> Unnecessary error check and message. devm_ioremap_resource()
>> returns an error if res is NULL.
>>
> 
> OK, I will fix it.
>   
>>> +
>>> +	wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
>>> +	if (IS_ERR(wdt->base))
>>
>> Move the error message to here.
>>
>>> +		return PTR_ERR(wdt->base);
>>> +
>>> +	wdt->enable = devm_clk_get(&pdev->dev, "enable");
>>> +	if (IS_ERR(wdt->enable)) {
>>> +		dev_err(&pdev->dev, "can't get the enable clock\n");
>>> +		return PTR_ERR(wdt->enable);
>>> +	}
>>> +
>>> +	wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
>>> +	if (IS_ERR(wdt->rtc_enable)) {
>>> +		dev_err(&pdev->dev, "can't get the rtc enable clock\n");
>>> +		return PTR_ERR(wdt->rtc_enable);
>>> +	}
>>> +
>>> +	wdt->irq = platform_get_irq(pdev, 0);
>>> +	if (wdt->irq < 0) {
>>> +		dev_err(&pdev->dev, "failed to get IRQ resource\n");
>>> +		return wdt->irq;
>>> +	}
>>> +
>>> +	ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
>>> +			       IRQF_NO_SUSPEND, "sprd-wdt", (void *)wdt);
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "failed to register irq\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	wdt->wdd.info = &sprd_wdt_info;
>>> +	wdt->wdd.ops = &sprd_wdt_ops;
>>> +	wdt->wdd.parent = &pdev->dev;
>>> +	wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
>>> +	wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
>>> +
>> You might want to set wdt->wdd.timeout to a default value.
>>
> 
> OK, I will set a default timeout value in case of no timeout-sec in device-tree.
>   
>>> +	ret = sprd_wdt_enable(wdt);
>>> +	if (ret) {
>>> +		dev_err(&pdev->dev, "failed to enable wdt\n");
>>> +		return ret;
>>> +	}
>>> +
>>
>> This needs a matching sprd_wdt_disable() call in the remove function.
>> Best way to handle this would be to add devm_add_action() here.
>>
> 
> If add devm_add_action(), it will be called in the remove function,
> but this is not our expect, if someone remove this module, we want it just timeout.
> 

But that leaves the watchdog enabled even if it was stopped (no call to
sprd_wdt_disable()).

Relying on NOWAYOUT would be a better option here. Again, you are
making a choice for the user.

>>> +	watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
>>> +	watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>> +
>>> +	ret = watchdog_register_device(&wdt->wdd);
>>
>> Unfortunately this doesn't work. It leaves interrupts enabled
>> after the watchdog device is removed in sprd_wdt_remove(),
>> but the driver will be gone. I would suggest to use
>> devm_watchdog_register_device() and reorder calls to request
>> the interrupt after registering the watchdog device. Then you
>> can drop the remove function entirely.
>>
> 
> Yes, you are right, I understand your opinion, and it is very important,
> devm_watchdog_register_device() is better. Thanks.
> 
>>> +	if (ret) {
>>> +		sprd_wdt_disable(wdt);
>>> +		dev_err(&pdev->dev, "failed to register watchdog\n");
>>> +		return ret;
>>> +	}
>>> +	platform_set_drvdata(pdev, wdt);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int sprd_wdt_remove(struct platform_device *pdev)
>>> +{
>>> +	struct sprd_wdt *wdt = platform_get_drvdata(pdev);
>>> +
>>> +	watchdog_unregister_device(&wdt->wdd);
>>> +
>>> +	if (sprd_wdt_is_running(wdt))
>>> +		dev_crit(&pdev->dev, "Device removed: Expect reboot!\n");
>>> +	return 0;
>>> +}
>>> +
>>> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
>>> +{
>>> +	struct watchdog_device *wdd = dev_get_drvdata(dev);
>>> +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>> +
>>> +	if (watchdog_active(wdd)) {
>>> +		sprd_wdt_stop(&wdt->wdd);
>>> +		sprd_wdt_disable(wdt);
>>
>> Are you sure you only want to disable the clocks if the watchdog was active ?
>> That seems to be a bit inconsistent.
>>
> 
> This watchdog is in always on power domain, if system suspend, it needs to
> disable it, or it will timeout.
> 
That is not what I asked. I asked why it isn't

	if (watchdog_active(wdd))
		sprd_wdt_stop(&wdt->wdd);

	sprd_wdt_disable(wdt);

instead.

>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
>>> +{
>>> +	struct watchdog_device *wdd = dev_get_drvdata(dev);
>>> +	struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>> +	int ret;
>>> +
>>> +	if (watchdog_active(wdd)) {
>>> +		ret = sprd_wdt_enable(wdt);
>>> +		if (ret)
>>> +			return ret;
>>> +		ret = sprd_wdt_start(&wdt->wdd);
>>> +		if (ret) {
>>> +			sprd_wdt_disable(wdt);
>>> +			return ret;
>>> +		}
>>
>> This can leave the system in an inconsistent state. Sometimes the wdt may be
>> disabled, sometimes not.
>>
> 
> If watchdog enable failed, it means there is something wrong in this system.
>   

True.

Guenter
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Hi Guenter,

(There are some problem with Eric's email, he can not receive this
email, so I help to reply his comments following yours. sorry for
troubles.)

>>>> +#define SPRD_WDT_MAX_TIMEOUT           60
>>>
>>>
>>> Is that really the maximum supported timeout ? Seems a bit low.
>>> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
>>>
>>
>> It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
>> but it doesn't unnecessary to support so big value, if the system can not
>> response it in 60s, the watchdog could trigger timeout.
>>
> It is customary to provide the highest possible value here.
> No one is forced to set such high values. You are making a choice for
> others here. But, sure, if you insist; not worth arguing about.

Eric said 60s is better for us, thanks for your patient explanation.

>
>>>> +
>>>> +#define SPRD_WDT_CNT_HIGH_VALUE                16
>>>
>>>
>>> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
>>> it is a shift.
>>>
>>
>> Yes, you are right, _SHIFT will be better.
>>
>>>>
>>>> +#define SPRD_WDT_LOW_VALUE_MASK                GENMASK(15, 0)
>>>> +#define SPRD_WDT_CNT_VALUE_MAX         GENMASK(31, 0)
>>>
>>>
>>> Does this mask serve a useful purpose ?
>>>
>>
>> OK, I will remove it, thanks!
>>
>>>> +#define SPRD_WDT_LOAD_TIMEOUT          1000
>>>> +
>>>> +struct sprd_wdt {
>>>> +       void __iomem *base;
>>>> +       struct watchdog_device wdd;
>>>> +       struct clk *enable;
>>>> +       struct clk *rtc_enable;
>>>> +       unsigned int irq;
>>>> +};
>>>> +
>>>> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
>>>> +{
>>>> +       return container_of(wdd, struct sprd_wdt, wdd);
>>>> +}
>>>> +
>>>> +static inline void sprd_wdt_lock(void __iomem *addr)
>>>> +{
>>>> +       writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
>>>> +}
>>>> +
>>>> +static inline void sprd_wdt_unlock(void __iomem *addr)
>>>> +{
>>>> +       writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
>>>> +}
>>>> +
>>>> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
>>>> +{
>>>> +       u32 val;
>>>> +
>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> +       return val & SPRD_WDT_NEW_VER_EN;
>>>> +}
>>>> +
>>>> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
>>>> +{
>>>> +       struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
>>>> +
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base +
>>>> SPRD_WDT_INT_CLR);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +       watchdog_notify_pretimeout(&wdt->wdd);
>>>> +       return IRQ_HANDLED;
>>>> +}
>>>> +
>>>> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
>>>> +{
>>>> +       u32 val;
>>>> +
>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
>>>> +               SPRD_WDT_CNT_HIGH_VALUE;
>>>> +       val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
>>>> +               SPRD_WDT_LOW_VALUE_MASK;
>>>> +
>>>> +       return val;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
>>>> +                              u32 pretimeout)
>>>> +{
>>>> +       u32 val, delay_cnt = 0;
>>>> +       u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
>>>> +       u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>>>> +
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>> +                     SPRD_WDT_LOW_VALUE_MASK, wdt->base +
>>>> SPRD_WDT_LOAD_HIGH);
>>>> +       writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
>>>> +                      wdt->base + SPRD_WDT_LOAD_LOW);
>>>> +       writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>> +                       SPRD_WDT_LOW_VALUE_MASK,
>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
>>>> +       writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +
>>>> +       /*
>>>> +        * Waiting the load value operation done,
>>>> +        * it needs two or three RTC clock cycles.
>>>> +        */
>>>> +       do {
>>>> +               val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
>>>> +               if (!(val & SPRD_WDT_LD_BUSY_BIT))
>>>> +                       break;
>>>> +
>>>> +               cpu_relax();
>>>> +       } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>>>> +
>>>> +       if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>>>> +               return -EBUSY;
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
>>>> +{
>>>> +       u32 val;
>>>> +       int ret;
>>>> +
>>>> +       ret = clk_prepare_enable(wdt->enable);
>>>> +       if (ret)
>>>> +               return ret;
>>>> +       ret = clk_prepare_enable(wdt->rtc_enable);
>>>> +       if (ret)
>>>> +               return ret;
>>>> +
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> +       val |= SPRD_WDT_NEW_VER_EN;
>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
>>>> +{
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +
>>>> +       clk_disable_unprepare(wdt->rtc_enable);
>>>> +       clk_disable_unprepare(wdt->enable);
>>>> +}
>>>> +
>>>> +static int sprd_wdt_start(struct watchdog_device *wdd)
>>>> +{
>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +       u32 val;
>>>> +       int ret;
>>>> +
>>>> +       ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
>>>> +       if (ret)
>>>> +               return ret;
>>>> +
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> +       val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT |
>>>> SPRD_WDT_RST_EN_BIT;
>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +       set_bit(WDOG_HW_RUNNING, &wdd->status);
>>>> +
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_stop(struct watchdog_device *wdd)
>>>> +{
>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +       u32 val;
>>>> +
>>>> +       sprd_wdt_unlock(wdt->base);
>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> +       val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
>>>> +               SPRD_WDT_INT_EN_BIT);
>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> +       sprd_wdt_lock(wdt->base);
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
>>>> +                               u32 timeout)
>>>> +{
>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +
>>>> +       if (timeout == wdd->timeout)
>>>> +               return 0;
>>>> +
>>>> +       wdd->timeout = timeout;
>>>> +
>>>> +       return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
>>>> +}
>>>> +
>>>> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
>>>> +                                  u32 new_pretimeout)
>>>> +{
>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +
>>>> +       if (new_pretimeout == wdd->pretimeout)
>>>> +               return 0;
>>>
>>>
>>> This is inconsistent. pretimeout == 0 is accepted until it is set
>>> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
>>> should reflect "pretimeout disabled". If that is not possible you
>>> need to set some non-0 default value in the probe function.
>>>
>>
>> I understand your opinion, I will fix it.
>>
>>>> +       if (new_pretimeout <= wdd->min_timeout)
>>>> +               return -EINVAL;
>>>
>>>
>>> Why is pretimeout == wdd->min_timeout invalid ?
>>>
>>
>> OK, you are right, it should be pretimeout < min_timeout.
>>
>>>> +
>>>> +       wdd->pretimeout = new_pretimeout;
>>>> +
>>>> +       return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
>>>> +}
>>>> +
>>>> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
>>>> +{
>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +       u32 val;
>>>> +
>>>> +       val = sprd_wdt_get_cnt_value(wdt);
>>>> +       val = val / SPRD_WDT_CNT_STEP;
>>>> +
>>>> +       return val;
>>>> +}
>>>> +
>>>> +static const struct watchdog_ops sprd_wdt_ops = {
>>>> +       .owner = THIS_MODULE,
>>>> +       .start = sprd_wdt_start,
>>>> +       .stop = sprd_wdt_stop,
>>>> +       .set_timeout = sprd_wdt_set_timeout,
>>>> +       .set_pretimeout = sprd_wdt_set_pretimeout,
>>>> +       .get_timeleft = sprd_wdt_get_timeleft,
>>>
>>>
>>> Just wondering - no heartbeat function ? Having to load the timer
>>> values for each heartbeat is expensive.
>>>
>>
>> Unfortunately, this watchdog has not RELOAD register.
>>
>>>>
>>>> +};
>>>> +
>>>> +static const struct watchdog_info sprd_wdt_info = {
>>>> +       .options = WDIOF_SETTIMEOUT |
>>>> +                  WDIOF_PRETIMEOUT |
>>>> +                  WDIOF_MAGICCLOSE |
>>>> +                  WDIOF_KEEPALIVEPING,
>>>> +       .identity = "Spreadtrum Watchdog Timer",
>>>> +};
>>>> +
>>>> +static int sprd_wdt_probe(struct platform_device *pdev)
>>>> +{
>>>> +       struct resource *wdt_res;
>>>> +       struct sprd_wdt *wdt;
>>>> +       int ret;
>>>> +
>>>> +       wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>>> +       if (!wdt)
>>>> +               return -ENOMEM;
>>>> +
>>>> +       wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> +       if (!wdt_res) {
>>>> +               dev_err(&pdev->dev, "failed to memory resource\n");
>>>> +               return -ENOMEM;
>>>> +       }
>>>
>>>
>>> Unnecessary error check and message. devm_ioremap_resource()
>>> returns an error if res is NULL.
>>>
>>
>> OK, I will fix it.
>>
>>>>
>>>> +
>>>> +       wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
>>>> +       if (IS_ERR(wdt->base))
>>>
>>>
>>> Move the error message to here.
>>>
>>>> +               return PTR_ERR(wdt->base);
>>>> +
>>>> +       wdt->enable = devm_clk_get(&pdev->dev, "enable");
>>>> +       if (IS_ERR(wdt->enable)) {
>>>> +               dev_err(&pdev->dev, "can't get the enable clock\n");
>>>> +               return PTR_ERR(wdt->enable);
>>>> +       }
>>>> +
>>>> +       wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
>>>> +       if (IS_ERR(wdt->rtc_enable)) {
>>>> +               dev_err(&pdev->dev, "can't get the rtc enable clock\n");
>>>> +               return PTR_ERR(wdt->rtc_enable);
>>>> +       }
>>>> +
>>>> +       wdt->irq = platform_get_irq(pdev, 0);
>>>> +       if (wdt->irq < 0) {
>>>> +               dev_err(&pdev->dev, "failed to get IRQ resource\n");
>>>> +               return wdt->irq;
>>>> +       }
>>>> +
>>>> +       ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
>>>> +                              IRQF_NO_SUSPEND, "sprd-wdt", (void
>>>> *)wdt);
>>>> +       if (ret) {
>>>> +               dev_err(&pdev->dev, "failed to register irq\n");
>>>> +               return ret;
>>>> +       }
>>>> +
>>>> +       wdt->wdd.info = &sprd_wdt_info;
>>>> +       wdt->wdd.ops = &sprd_wdt_ops;
>>>> +       wdt->wdd.parent = &pdev->dev;
>>>> +       wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
>>>> +       wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
>>>> +
>>>
>>> You might want to set wdt->wdd.timeout to a default value.
>>>
>>
>> OK, I will set a default timeout value in case of no timeout-sec in
>> device-tree.
>>
>>>>
>>>> +       ret = sprd_wdt_enable(wdt);
>>>> +       if (ret) {
>>>> +               dev_err(&pdev->dev, "failed to enable wdt\n");
>>>> +               return ret;
>>>> +       }
>>>> +
>>>
>>>
>>> This needs a matching sprd_wdt_disable() call in the remove function.
>>> Best way to handle this would be to add devm_add_action() here.
>>>
>>
>> If add devm_add_action(), it will be called in the remove function,
>> but this is not our expect, if someone remove this module, we want it just
>> timeout.
>>
>
> But that leaves the watchdog enabled even if it was stopped (no call to
> sprd_wdt_disable()).

Eric said It can not be stopped since we have set WATCHDOG_NOWAYOUT,
which means it will reboot the system when removing the watchdog.

> Relying on NOWAYOUT would be a better option here. Again, you are
> making a choice for the user.

we have set WATCHDOG_NOWAYOUT.

>
>
>>>> +       watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
>>>> +       watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>>> +
>>>> +       ret = watchdog_register_device(&wdt->wdd);
>>>
>>>
>>> Unfortunately this doesn't work. It leaves interrupts enabled
>>> after the watchdog device is removed in sprd_wdt_remove(),
>>> but the driver will be gone. I would suggest to use
>>> devm_watchdog_register_device() and reorder calls to request
>>> the interrupt after registering the watchdog device. Then you
>>> can drop the remove function entirely.
>>>
>>
>> Yes, you are right, I understand your opinion, and it is very important,
>> devm_watchdog_register_device() is better. Thanks.
>>
>>>> +       if (ret) {
>>>> +               sprd_wdt_disable(wdt);
>>>> +               dev_err(&pdev->dev, "failed to register watchdog\n");
>>>> +               return ret;
>>>> +       }
>>>> +       platform_set_drvdata(pdev, wdt);
>>>> +
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_remove(struct platform_device *pdev)
>>>> +{
>>>> +       struct sprd_wdt *wdt = platform_get_drvdata(pdev);
>>>> +
>>>> +       watchdog_unregister_device(&wdt->wdd);
>>>> +
>>>> +       if (sprd_wdt_is_running(wdt))
>>>> +               dev_crit(&pdev->dev, "Device removed: Expect
>>>> reboot!\n");
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
>>>> +{
>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>> +
>>>> +       if (watchdog_active(wdd)) {
>>>> +               sprd_wdt_stop(&wdt->wdd);
>>>> +               sprd_wdt_disable(wdt);
>>>
>>>
>>> Are you sure you only want to disable the clocks if the watchdog was
>>> active ?
>>> That seems to be a bit inconsistent.
>>>
>>
>> This watchdog is in always on power domain, if system suspend, it needs to
>> disable it, or it will timeout.
>>
> That is not what I asked. I asked why it isn't
>
>         if (watchdog_active(wdd))
>                 sprd_wdt_stop(&wdt->wdd);
>
>         sprd_wdt_disable(wdt);
>
> instead.

Yes, Eric will fix this in next version.

>
>>>> +       }
>>>> +
>>>> +       return 0;
>>>> +}
>>>> +
>>>> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
>>>> +{
>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>> +       int ret;
>>>> +
>>>> +       if (watchdog_active(wdd)) {
>>>> +               ret = sprd_wdt_enable(wdt);
>>>> +               if (ret)
>>>> +                       return ret;
>>>> +               ret = sprd_wdt_start(&wdt->wdd);
>>>> +               if (ret) {
>>>> +                       sprd_wdt_disable(wdt);
>>>> +                       return ret;
>>>> +               }
>>>
>>>
>>> This can leave the system in an inconsistent state. Sometimes the wdt may
>>> be
>>> disabled, sometimes not.
>>>
>>
>> If watchdog enable failed, it means there is something wrong in this
>> system.
>>
>
>
> True.
>
> Guenter

On 10/30/2017 02:18 AM, Baolin Wang wrote:
> Hi Guenter,
> 
> (There are some problem with Eric's email, he can not receive this
> email, so I help to reply his comments following yours. sorry for
> troubles.)
> 
>>>>> +#define SPRD_WDT_MAX_TIMEOUT           60
>>>>
>>>>
>>>> Is that really the maximum supported timeout ? Seems a bit low.
>>>> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
>>>>
>>>
>>> It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
>>> but it doesn't unnecessary to support so big value, if the system can not
>>> response it in 60s, the watchdog could trigger timeout.
>>>
>> It is customary to provide the highest possible value here.
>> No one is forced to set such high values. You are making a choice for
>> others here. But, sure, if you insist; not worth arguing about.
> 
> Eric said 60s is better for us, thanks for your patient explanation.
> 
>>
>>>>> +
>>>>> +#define SPRD_WDT_CNT_HIGH_VALUE                16
>>>>
>>>>
>>>> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
>>>> it is a shift.
>>>>
>>>
>>> Yes, you are right, _SHIFT will be better.
>>>
>>>>>
>>>>> +#define SPRD_WDT_LOW_VALUE_MASK                GENMASK(15, 0)
>>>>> +#define SPRD_WDT_CNT_VALUE_MAX         GENMASK(31, 0)
>>>>
>>>>
>>>> Does this mask serve a useful purpose ?
>>>>
>>>
>>> OK, I will remove it, thanks!
>>>
>>>>> +#define SPRD_WDT_LOAD_TIMEOUT          1000
>>>>> +
>>>>> +struct sprd_wdt {
>>>>> +       void __iomem *base;
>>>>> +       struct watchdog_device wdd;
>>>>> +       struct clk *enable;
>>>>> +       struct clk *rtc_enable;
>>>>> +       unsigned int irq;
>>>>> +};
>>>>> +
>>>>> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
>>>>> +{
>>>>> +       return container_of(wdd, struct sprd_wdt, wdd);
>>>>> +}
>>>>> +
>>>>> +static inline void sprd_wdt_lock(void __iomem *addr)
>>>>> +{
>>>>> +       writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
>>>>> +}
>>>>> +
>>>>> +static inline void sprd_wdt_unlock(void __iomem *addr)
>>>>> +{
>>>>> +       writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
>>>>> +}
>>>>> +
>>>>> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
>>>>> +{
>>>>> +       u32 val;
>>>>> +
>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>> +       return val & SPRD_WDT_NEW_VER_EN;
>>>>> +}
>>>>> +
>>>>> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
>>>>> +
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base +
>>>>> SPRD_WDT_INT_CLR);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +       watchdog_notify_pretimeout(&wdt->wdd);
>>>>> +       return IRQ_HANDLED;
>>>>> +}
>>>>> +
>>>>> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
>>>>> +{
>>>>> +       u32 val;
>>>>> +
>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
>>>>> +               SPRD_WDT_CNT_HIGH_VALUE;
>>>>> +       val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
>>>>> +               SPRD_WDT_LOW_VALUE_MASK;
>>>>> +
>>>>> +       return val;
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
>>>>> +                              u32 pretimeout)
>>>>> +{
>>>>> +       u32 val, delay_cnt = 0;
>>>>> +       u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
>>>>> +       u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>>>>> +
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>>> +                     SPRD_WDT_LOW_VALUE_MASK, wdt->base +
>>>>> SPRD_WDT_LOAD_HIGH);
>>>>> +       writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
>>>>> +                      wdt->base + SPRD_WDT_LOAD_LOW);
>>>>> +       writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>>> +                       SPRD_WDT_LOW_VALUE_MASK,
>>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
>>>>> +       writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
>>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +
>>>>> +       /*
>>>>> +        * Waiting the load value operation done,
>>>>> +        * it needs two or three RTC clock cycles.
>>>>> +        */
>>>>> +       do {
>>>>> +               val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
>>>>> +               if (!(val & SPRD_WDT_LD_BUSY_BIT))
>>>>> +                       break;
>>>>> +
>>>>> +               cpu_relax();
>>>>> +       } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>>>>> +
>>>>> +       if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>>>>> +               return -EBUSY;
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
>>>>> +{
>>>>> +       u32 val;
>>>>> +       int ret;
>>>>> +
>>>>> +       ret = clk_prepare_enable(wdt->enable);
>>>>> +       if (ret)
>>>>> +               return ret;
>>>>> +       ret = clk_prepare_enable(wdt->rtc_enable);
>>>>> +       if (ret)
>>>>> +               return ret;
>>>>> +
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>> +       val |= SPRD_WDT_NEW_VER_EN;
>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
>>>>> +{
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +
>>>>> +       clk_disable_unprepare(wdt->rtc_enable);
>>>>> +       clk_disable_unprepare(wdt->enable);
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_start(struct watchdog_device *wdd)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>> +       u32 val;
>>>>> +       int ret;
>>>>> +
>>>>> +       ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
>>>>> +       if (ret)
>>>>> +               return ret;
>>>>> +
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>> +       val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT |
>>>>> SPRD_WDT_RST_EN_BIT;
>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +       set_bit(WDOG_HW_RUNNING, &wdd->status);
>>>>> +
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_stop(struct watchdog_device *wdd)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>> +       u32 val;
>>>>> +
>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>> +       val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
>>>>> +               SPRD_WDT_INT_EN_BIT);
>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>> +       sprd_wdt_lock(wdt->base);
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
>>>>> +                               u32 timeout)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>> +
>>>>> +       if (timeout == wdd->timeout)
>>>>> +               return 0;
>>>>> +
>>>>> +       wdd->timeout = timeout;
>>>>> +
>>>>> +       return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
>>>>> +                                  u32 new_pretimeout)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>> +
>>>>> +       if (new_pretimeout == wdd->pretimeout)
>>>>> +               return 0;
>>>>
>>>>
>>>> This is inconsistent. pretimeout == 0 is accepted until it is set
>>>> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
>>>> should reflect "pretimeout disabled". If that is not possible you
>>>> need to set some non-0 default value in the probe function.
>>>>
>>>
>>> I understand your opinion, I will fix it.
>>>
>>>>> +       if (new_pretimeout <= wdd->min_timeout)
>>>>> +               return -EINVAL;
>>>>
>>>>
>>>> Why is pretimeout == wdd->min_timeout invalid ?
>>>>
>>>
>>> OK, you are right, it should be pretimeout < min_timeout.
>>>
>>>>> +
>>>>> +       wdd->pretimeout = new_pretimeout;
>>>>> +
>>>>> +       return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
>>>>> +}
>>>>> +
>>>>> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>> +       u32 val;
>>>>> +
>>>>> +       val = sprd_wdt_get_cnt_value(wdt);
>>>>> +       val = val / SPRD_WDT_CNT_STEP;
>>>>> +
>>>>> +       return val;
>>>>> +}
>>>>> +
>>>>> +static const struct watchdog_ops sprd_wdt_ops = {
>>>>> +       .owner = THIS_MODULE,
>>>>> +       .start = sprd_wdt_start,
>>>>> +       .stop = sprd_wdt_stop,
>>>>> +       .set_timeout = sprd_wdt_set_timeout,
>>>>> +       .set_pretimeout = sprd_wdt_set_pretimeout,
>>>>> +       .get_timeleft = sprd_wdt_get_timeleft,
>>>>
>>>>
>>>> Just wondering - no heartbeat function ? Having to load the timer
>>>> values for each heartbeat is expensive.
>>>>
>>>
>>> Unfortunately, this watchdog has not RELOAD register.
>>>
>>>>>
>>>>> +};
>>>>> +
>>>>> +static const struct watchdog_info sprd_wdt_info = {
>>>>> +       .options = WDIOF_SETTIMEOUT |
>>>>> +                  WDIOF_PRETIMEOUT |
>>>>> +                  WDIOF_MAGICCLOSE |
>>>>> +                  WDIOF_KEEPALIVEPING,
>>>>> +       .identity = "Spreadtrum Watchdog Timer",
>>>>> +};
>>>>> +
>>>>> +static int sprd_wdt_probe(struct platform_device *pdev)
>>>>> +{
>>>>> +       struct resource *wdt_res;
>>>>> +       struct sprd_wdt *wdt;
>>>>> +       int ret;
>>>>> +
>>>>> +       wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>>>> +       if (!wdt)
>>>>> +               return -ENOMEM;
>>>>> +
>>>>> +       wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>>> +       if (!wdt_res) {
>>>>> +               dev_err(&pdev->dev, "failed to memory resource\n");
>>>>> +               return -ENOMEM;
>>>>> +       }
>>>>
>>>>
>>>> Unnecessary error check and message. devm_ioremap_resource()
>>>> returns an error if res is NULL.
>>>>
>>>
>>> OK, I will fix it.
>>>
>>>>>
>>>>> +
>>>>> +       wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
>>>>> +       if (IS_ERR(wdt->base))
>>>>
>>>>
>>>> Move the error message to here.
>>>>
>>>>> +               return PTR_ERR(wdt->base);
>>>>> +
>>>>> +       wdt->enable = devm_clk_get(&pdev->dev, "enable");
>>>>> +       if (IS_ERR(wdt->enable)) {
>>>>> +               dev_err(&pdev->dev, "can't get the enable clock\n");
>>>>> +               return PTR_ERR(wdt->enable);
>>>>> +       }
>>>>> +
>>>>> +       wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
>>>>> +       if (IS_ERR(wdt->rtc_enable)) {
>>>>> +               dev_err(&pdev->dev, "can't get the rtc enable clock\n");
>>>>> +               return PTR_ERR(wdt->rtc_enable);
>>>>> +       }
>>>>> +
>>>>> +       wdt->irq = platform_get_irq(pdev, 0);
>>>>> +       if (wdt->irq < 0) {
>>>>> +               dev_err(&pdev->dev, "failed to get IRQ resource\n");
>>>>> +               return wdt->irq;
>>>>> +       }
>>>>> +
>>>>> +       ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
>>>>> +                              IRQF_NO_SUSPEND, "sprd-wdt", (void
>>>>> *)wdt);
>>>>> +       if (ret) {
>>>>> +               dev_err(&pdev->dev, "failed to register irq\n");
>>>>> +               return ret;
>>>>> +       }
>>>>> +
>>>>> +       wdt->wdd.info = &sprd_wdt_info;
>>>>> +       wdt->wdd.ops = &sprd_wdt_ops;
>>>>> +       wdt->wdd.parent = &pdev->dev;
>>>>> +       wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
>>>>> +       wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
>>>>> +
>>>>
>>>> You might want to set wdt->wdd.timeout to a default value.
>>>>
>>>
>>> OK, I will set a default timeout value in case of no timeout-sec in
>>> device-tree.
>>>
>>>>>
>>>>> +       ret = sprd_wdt_enable(wdt);
>>>>> +       if (ret) {
>>>>> +               dev_err(&pdev->dev, "failed to enable wdt\n");
>>>>> +               return ret;
>>>>> +       }
>>>>> +
>>>>
>>>>
>>>> This needs a matching sprd_wdt_disable() call in the remove function.
>>>> Best way to handle this would be to add devm_add_action() here.
>>>>
>>>
>>> If add devm_add_action(), it will be called in the remove function,
>>> but this is not our expect, if someone remove this module, we want it just
>>> timeout.
>>>
>>
>> But that leaves the watchdog enabled even if it was stopped (no call to
>> sprd_wdt_disable()).
> 
> Eric said It can not be stopped since we have set WATCHDOG_NOWAYOUT,
> which means it will reboot the system when removing the watchdog.
> 
>> Relying on NOWAYOUT would be a better option here. Again, you are
>> making a choice for the user.
> 
> we have set WATCHDOG_NOWAYOUT.
> 
Yes, I understand, but that is configurable.

Guenter

>>
>>
>>>>> +       watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
>>>>> +       watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>>>> +
>>>>> +       ret = watchdog_register_device(&wdt->wdd);
>>>>
>>>>
>>>> Unfortunately this doesn't work. It leaves interrupts enabled
>>>> after the watchdog device is removed in sprd_wdt_remove(),
>>>> but the driver will be gone. I would suggest to use
>>>> devm_watchdog_register_device() and reorder calls to request
>>>> the interrupt after registering the watchdog device. Then you
>>>> can drop the remove function entirely.
>>>>
>>>
>>> Yes, you are right, I understand your opinion, and it is very important,
>>> devm_watchdog_register_device() is better. Thanks.
>>>
>>>>> +       if (ret) {
>>>>> +               sprd_wdt_disable(wdt);
>>>>> +               dev_err(&pdev->dev, "failed to register watchdog\n");
>>>>> +               return ret;
>>>>> +       }
>>>>> +       platform_set_drvdata(pdev, wdt);
>>>>> +
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int sprd_wdt_remove(struct platform_device *pdev)
>>>>> +{
>>>>> +       struct sprd_wdt *wdt = platform_get_drvdata(pdev);
>>>>> +
>>>>> +       watchdog_unregister_device(&wdt->wdd);
>>>>> +
>>>>> +       if (sprd_wdt_is_running(wdt))
>>>>> +               dev_crit(&pdev->dev, "Device removed: Expect
>>>>> reboot!\n");
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
>>>>> +{
>>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>>> +
>>>>> +       if (watchdog_active(wdd)) {
>>>>> +               sprd_wdt_stop(&wdt->wdd);
>>>>> +               sprd_wdt_disable(wdt);
>>>>
>>>>
>>>> Are you sure you only want to disable the clocks if the watchdog was
>>>> active ?
>>>> That seems to be a bit inconsistent.
>>>>
>>>
>>> This watchdog is in always on power domain, if system suspend, it needs to
>>> disable it, or it will timeout.
>>>
>> That is not what I asked. I asked why it isn't
>>
>>          if (watchdog_active(wdd))
>>                  sprd_wdt_stop(&wdt->wdd);
>>
>>          sprd_wdt_disable(wdt);
>>
>> instead.
> 
> Yes, Eric will fix this in next version.
> 
>>
>>>>> +       }
>>>>> +
>>>>> +       return 0;
>>>>> +}
>>>>> +
>>>>> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
>>>>> +{
>>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>>> +       int ret;
>>>>> +
>>>>> +       if (watchdog_active(wdd)) {
>>>>> +               ret = sprd_wdt_enable(wdt);
>>>>> +               if (ret)
>>>>> +                       return ret;
>>>>> +               ret = sprd_wdt_start(&wdt->wdd);
>>>>> +               if (ret) {
>>>>> +                       sprd_wdt_disable(wdt);
>>>>> +                       return ret;
>>>>> +               }
>>>>
>>>>
>>>> This can leave the system in an inconsistent state. Sometimes the wdt may
>>>> be
>>>> disabled, sometimes not.
>>>>
>>>
>>> If watchdog enable failed, it means there is something wrong in this
>>> system.
>>>
>>
>>
>> True.
>>
>> Guenter
> 
> 
> 

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Hi,

On 30 October 2017 at 17:32, Guenter Roeck <linux@roeck-us.net> wrote:
> On 10/30/2017 02:18 AM, Baolin Wang wrote:
>>
>> Hi Guenter,
>>
>> (There are some problem with Eric's email, he can not receive this
>> email, so I help to reply his comments following yours. sorry for
>> troubles.)
>>
>>>>>> +#define SPRD_WDT_MAX_TIMEOUT           60
>>>>>
>>>>>
>>>>>
>>>>> Is that really the maximum supported timeout ? Seems a bit low.
>>>>> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
>>>>>
>>>>
>>>> It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
>>>> but it doesn't unnecessary to support so big value, if the system can
>>>> not
>>>> response it in 60s, the watchdog could trigger timeout.
>>>>
>>> It is customary to provide the highest possible value here.
>>> No one is forced to set such high values. You are making a choice for
>>> others here. But, sure, if you insist; not worth arguing about.
>>
>>
>> Eric said 60s is better for us, thanks for your patient explanation.
>>
>>>
>>>>>> +
>>>>>> +#define SPRD_WDT_CNT_HIGH_VALUE                16
>>>>>
>>>>>
>>>>>
>>>>> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
>>>>> it is a shift.
>>>>>
>>>>
>>>> Yes, you are right, _SHIFT will be better.
>>>>
>>>>>>
>>>>>> +#define SPRD_WDT_LOW_VALUE_MASK                GENMASK(15, 0)
>>>>>> +#define SPRD_WDT_CNT_VALUE_MAX         GENMASK(31, 0)
>>>>>
>>>>>
>>>>>
>>>>> Does this mask serve a useful purpose ?
>>>>>
>>>>
>>>> OK, I will remove it, thanks!
>>>>
>>>>>> +#define SPRD_WDT_LOAD_TIMEOUT          1000
>>>>>> +
>>>>>> +struct sprd_wdt {
>>>>>> +       void __iomem *base;
>>>>>> +       struct watchdog_device wdd;
>>>>>> +       struct clk *enable;
>>>>>> +       struct clk *rtc_enable;
>>>>>> +       unsigned int irq;
>>>>>> +};
>>>>>> +
>>>>>> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device
>>>>>> *wdd)
>>>>>> +{
>>>>>> +       return container_of(wdd, struct sprd_wdt, wdd);
>>>>>> +}
>>>>>> +
>>>>>> +static inline void sprd_wdt_lock(void __iomem *addr)
>>>>>> +{
>>>>>> +       writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
>>>>>> +}
>>>>>> +
>>>>>> +static inline void sprd_wdt_unlock(void __iomem *addr)
>>>>>> +{
>>>>>> +       writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
>>>>>> +}
>>>>>> +
>>>>>> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
>>>>>> +{
>>>>>> +       u32 val;
>>>>>> +
>>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>>> +       return val & SPRD_WDT_NEW_VER_EN;
>>>>>> +}
>>>>>> +
>>>>>> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
>>>>>> +
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base +
>>>>>> SPRD_WDT_INT_CLR);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +       watchdog_notify_pretimeout(&wdt->wdd);
>>>>>> +       return IRQ_HANDLED;
>>>>>> +}
>>>>>> +
>>>>>> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
>>>>>> +{
>>>>>> +       u32 val;
>>>>>> +
>>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
>>>>>> +               SPRD_WDT_CNT_HIGH_VALUE;
>>>>>> +       val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
>>>>>> +               SPRD_WDT_LOW_VALUE_MASK;
>>>>>> +
>>>>>> +       return val;
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
>>>>>> +                              u32 pretimeout)
>>>>>> +{
>>>>>> +       u32 val, delay_cnt = 0;
>>>>>> +       u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
>>>>>> +       u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>>>>>> +
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>>>> +                     SPRD_WDT_LOW_VALUE_MASK, wdt->base +
>>>>>> SPRD_WDT_LOAD_HIGH);
>>>>>> +       writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
>>>>>> +                      wdt->base + SPRD_WDT_LOAD_LOW);
>>>>>> +       writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>>>> +                       SPRD_WDT_LOW_VALUE_MASK,
>>>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
>>>>>> +       writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
>>>>>> +                      wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +
>>>>>> +       /*
>>>>>> +        * Waiting the load value operation done,
>>>>>> +        * it needs two or three RTC clock cycles.
>>>>>> +        */
>>>>>> +       do {
>>>>>> +               val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
>>>>>> +               if (!(val & SPRD_WDT_LD_BUSY_BIT))
>>>>>> +                       break;
>>>>>> +
>>>>>> +               cpu_relax();
>>>>>> +       } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>>>>>> +
>>>>>> +       if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>>>>>> +               return -EBUSY;
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
>>>>>> +{
>>>>>> +       u32 val;
>>>>>> +       int ret;
>>>>>> +
>>>>>> +       ret = clk_prepare_enable(wdt->enable);
>>>>>> +       if (ret)
>>>>>> +               return ret;
>>>>>> +       ret = clk_prepare_enable(wdt->rtc_enable);
>>>>>> +       if (ret)
>>>>>> +               return ret;
>>>>>> +
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>>> +       val |= SPRD_WDT_NEW_VER_EN;
>>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
>>>>>> +{
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +
>>>>>> +       clk_disable_unprepare(wdt->rtc_enable);
>>>>>> +       clk_disable_unprepare(wdt->enable);
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_start(struct watchdog_device *wdd)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>>> +       u32 val;
>>>>>> +       int ret;
>>>>>> +
>>>>>> +       ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
>>>>>> +       if (ret)
>>>>>> +               return ret;
>>>>>> +
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>>> +       val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT |
>>>>>> SPRD_WDT_RST_EN_BIT;
>>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +       set_bit(WDOG_HW_RUNNING, &wdd->status);
>>>>>> +
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_stop(struct watchdog_device *wdd)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>>> +       u32 val;
>>>>>> +
>>>>>> +       sprd_wdt_unlock(wdt->base);
>>>>>> +       val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>>>> +       val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
>>>>>> +               SPRD_WDT_INT_EN_BIT);
>>>>>> +       writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>>>> +       sprd_wdt_lock(wdt->base);
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
>>>>>> +                               u32 timeout)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>>> +
>>>>>> +       if (timeout == wdd->timeout)
>>>>>> +               return 0;
>>>>>> +
>>>>>> +       wdd->timeout = timeout;
>>>>>> +
>>>>>> +       return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
>>>>>> +                                  u32 new_pretimeout)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>>> +
>>>>>> +       if (new_pretimeout == wdd->pretimeout)
>>>>>> +               return 0;
>>>>>
>>>>>
>>>>>
>>>>> This is inconsistent. pretimeout == 0 is accepted until it is set
>>>>> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
>>>>> should reflect "pretimeout disabled". If that is not possible you
>>>>> need to set some non-0 default value in the probe function.
>>>>>
>>>>
>>>> I understand your opinion, I will fix it.
>>>>
>>>>>> +       if (new_pretimeout <= wdd->min_timeout)
>>>>>> +               return -EINVAL;
>>>>>
>>>>>
>>>>>
>>>>> Why is pretimeout == wdd->min_timeout invalid ?
>>>>>
>>>>
>>>> OK, you are right, it should be pretimeout < min_timeout.
>>>>
>>>>>> +
>>>>>> +       wdd->pretimeout = new_pretimeout;
>>>>>> +
>>>>>> +       return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
>>>>>> +}
>>>>>> +
>>>>>> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>>>> +       u32 val;
>>>>>> +
>>>>>> +       val = sprd_wdt_get_cnt_value(wdt);
>>>>>> +       val = val / SPRD_WDT_CNT_STEP;
>>>>>> +
>>>>>> +       return val;
>>>>>> +}
>>>>>> +
>>>>>> +static const struct watchdog_ops sprd_wdt_ops = {
>>>>>> +       .owner = THIS_MODULE,
>>>>>> +       .start = sprd_wdt_start,
>>>>>> +       .stop = sprd_wdt_stop,
>>>>>> +       .set_timeout = sprd_wdt_set_timeout,
>>>>>> +       .set_pretimeout = sprd_wdt_set_pretimeout,
>>>>>> +       .get_timeleft = sprd_wdt_get_timeleft,
>>>>>
>>>>>
>>>>>
>>>>> Just wondering - no heartbeat function ? Having to load the timer
>>>>> values for each heartbeat is expensive.
>>>>>
>>>>
>>>> Unfortunately, this watchdog has not RELOAD register.
>>>>
>>>>>>
>>>>>> +};
>>>>>> +
>>>>>> +static const struct watchdog_info sprd_wdt_info = {
>>>>>> +       .options = WDIOF_SETTIMEOUT |
>>>>>> +                  WDIOF_PRETIMEOUT |
>>>>>> +                  WDIOF_MAGICCLOSE |
>>>>>> +                  WDIOF_KEEPALIVEPING,
>>>>>> +       .identity = "Spreadtrum Watchdog Timer",
>>>>>> +};
>>>>>> +
>>>>>> +static int sprd_wdt_probe(struct platform_device *pdev)
>>>>>> +{
>>>>>> +       struct resource *wdt_res;
>>>>>> +       struct sprd_wdt *wdt;
>>>>>> +       int ret;
>>>>>> +
>>>>>> +       wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>>>>> +       if (!wdt)
>>>>>> +               return -ENOMEM;
>>>>>> +
>>>>>> +       wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>>>> +       if (!wdt_res) {
>>>>>> +               dev_err(&pdev->dev, "failed to memory resource\n");
>>>>>> +               return -ENOMEM;
>>>>>> +       }
>>>>>
>>>>>
>>>>>
>>>>> Unnecessary error check and message. devm_ioremap_resource()
>>>>> returns an error if res is NULL.
>>>>>
>>>>
>>>> OK, I will fix it.
>>>>
>>>>>>
>>>>>> +
>>>>>> +       wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
>>>>>> +       if (IS_ERR(wdt->base))
>>>>>
>>>>>
>>>>>
>>>>> Move the error message to here.
>>>>>
>>>>>> +               return PTR_ERR(wdt->base);
>>>>>> +
>>>>>> +       wdt->enable = devm_clk_get(&pdev->dev, "enable");
>>>>>> +       if (IS_ERR(wdt->enable)) {
>>>>>> +               dev_err(&pdev->dev, "can't get the enable clock\n");
>>>>>> +               return PTR_ERR(wdt->enable);
>>>>>> +       }
>>>>>> +
>>>>>> +       wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
>>>>>> +       if (IS_ERR(wdt->rtc_enable)) {
>>>>>> +               dev_err(&pdev->dev, "can't get the rtc enable
>>>>>> clock\n");
>>>>>> +               return PTR_ERR(wdt->rtc_enable);
>>>>>> +       }
>>>>>> +
>>>>>> +       wdt->irq = platform_get_irq(pdev, 0);
>>>>>> +       if (wdt->irq < 0) {
>>>>>> +               dev_err(&pdev->dev, "failed to get IRQ resource\n");
>>>>>> +               return wdt->irq;
>>>>>> +       }
>>>>>> +
>>>>>> +       ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
>>>>>> +                              IRQF_NO_SUSPEND, "sprd-wdt", (void
>>>>>> *)wdt);
>>>>>> +       if (ret) {
>>>>>> +               dev_err(&pdev->dev, "failed to register irq\n");
>>>>>> +               return ret;
>>>>>> +       }
>>>>>> +
>>>>>> +       wdt->wdd.info = &sprd_wdt_info;
>>>>>> +       wdt->wdd.ops = &sprd_wdt_ops;
>>>>>> +       wdt->wdd.parent = &pdev->dev;
>>>>>> +       wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
>>>>>> +       wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
>>>>>> +
>>>>>
>>>>>
>>>>> You might want to set wdt->wdd.timeout to a default value.
>>>>>
>>>>
>>>> OK, I will set a default timeout value in case of no timeout-sec in
>>>> device-tree.
>>>>
>>>>>>
>>>>>> +       ret = sprd_wdt_enable(wdt);
>>>>>> +       if (ret) {
>>>>>> +               dev_err(&pdev->dev, "failed to enable wdt\n");
>>>>>> +               return ret;
>>>>>> +       }
>>>>>> +
>>>>>
>>>>>
>>>>>
>>>>> This needs a matching sprd_wdt_disable() call in the remove function.
>>>>> Best way to handle this would be to add devm_add_action() here.
>>>>>
>>>>
>>>> If add devm_add_action(), it will be called in the remove function,
>>>> but this is not our expect, if someone remove this module, we want it
>>>> just
>>>> timeout.
>>>>
>>>
>>> But that leaves the watchdog enabled even if it was stopped (no call to
>>> sprd_wdt_disable()).
>>
>>
>> Eric said It can not be stopped since we have set WATCHDOG_NOWAYOUT,
>> which means it will reboot the system when removing the watchdog.
>>
>>> Relying on NOWAYOUT would be a better option here. Again, you are
>>> making a choice for the user.
>>
>>
>> we have set WATCHDOG_NOWAYOUT.
>>
> Yes, I understand, but that is configurable.

Yes, you are right. So I think we need add test_bit(WDOG_NO_WAY_OUT,
&wdd->status) in remove function to decide if we should issue
sprd_wdt_disable().


>>>
>>>
>>>>>> +       watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
>>>>>> +       watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>>>>> +
>>>>>> +       ret = watchdog_register_device(&wdt->wdd);
>>>>>
>>>>>
>>>>>
>>>>> Unfortunately this doesn't work. It leaves interrupts enabled
>>>>> after the watchdog device is removed in sprd_wdt_remove(),
>>>>> but the driver will be gone. I would suggest to use
>>>>> devm_watchdog_register_device() and reorder calls to request
>>>>> the interrupt after registering the watchdog device. Then you
>>>>> can drop the remove function entirely.
>>>>>
>>>>
>>>> Yes, you are right, I understand your opinion, and it is very important,
>>>> devm_watchdog_register_device() is better. Thanks.
>>>>
>>>>>> +       if (ret) {
>>>>>> +               sprd_wdt_disable(wdt);
>>>>>> +               dev_err(&pdev->dev, "failed to register watchdog\n");
>>>>>> +               return ret;
>>>>>> +       }
>>>>>> +       platform_set_drvdata(pdev, wdt);
>>>>>> +
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int sprd_wdt_remove(struct platform_device *pdev)
>>>>>> +{
>>>>>> +       struct sprd_wdt *wdt = platform_get_drvdata(pdev);
>>>>>> +
>>>>>> +       watchdog_unregister_device(&wdt->wdd);
>>>>>> +
>>>>>> +       if (sprd_wdt_is_running(wdt))
>>>>>> +               dev_crit(&pdev->dev, "Device removed: Expect
>>>>>> reboot!\n");
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
>>>>>> +{
>>>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>>>> +
>>>>>> +       if (watchdog_active(wdd)) {
>>>>>> +               sprd_wdt_stop(&wdt->wdd);
>>>>>> +               sprd_wdt_disable(wdt);
>>>>>
>>>>>
>>>>>
>>>>> Are you sure you only want to disable the clocks if the watchdog was
>>>>> active ?
>>>>> That seems to be a bit inconsistent.
>>>>>
>>>>
>>>> This watchdog is in always on power domain, if system suspend, it needs
>>>> to
>>>> disable it, or it will timeout.
>>>>
>>> That is not what I asked. I asked why it isn't
>>>
>>>          if (watchdog_active(wdd))
>>>                  sprd_wdt_stop(&wdt->wdd);
>>>
>>>          sprd_wdt_disable(wdt);
>>>
>>> instead.
>>
>>
>> Yes, Eric will fix this in next version.
>>
>>>
>>>>>> +       }
>>>>>> +
>>>>>> +       return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
>>>>>> +{
>>>>>> +       struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>>>> +       struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>>>> +       int ret;
>>>>>> +
>>>>>> +       if (watchdog_active(wdd)) {
>>>>>> +               ret = sprd_wdt_enable(wdt);
>>>>>> +               if (ret)
>>>>>> +                       return ret;
>>>>>> +               ret = sprd_wdt_start(&wdt->wdd);
>>>>>> +               if (ret) {
>>>>>> +                       sprd_wdt_disable(wdt);
>>>>>> +                       return ret;
>>>>>> +               }
>>>>>
>>>>>
>>>>>
>>>>> This can leave the system in an inconsistent state. Sometimes the wdt
>>>>> may
>>>>> be
>>>>> disabled, sometimes not.
>>>>>
>>>>
>>>> If watchdog enable failed, it means there is something wrong in this
>>>> system.
>>>>
>>>
>>>
>>> True.
>>>
>>> Guenter
>>
>>
>>
>>
>