Patchwork [v3] rtc: snvs: add Freescale rtc-snvs driver

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Submitter Shawn Guo
Date July 13, 2012, 7:31 a.m.
Message ID <1342164663-31351-1-git-send-email-shawn.guo@linaro.org>
Download mbox | patch
Permalink /patch/170801/
State New
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Comments

Shawn Guo - July 13, 2012, 7:31 a.m.
Add an RTC driver for Freescale Secure Non-Volatile Storage (SNVS)
Low Power (LP) RTC.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
---
Changes since v2:
 * Use SIMPLE_DEV_PM_OPS to save one #ifdef as suggested by Stephen

 .../devicetree/bindings/crypto/fsl-sec4.txt        |   51 +++
 Documentation/devicetree/bindings/rtc/snvs-rtc.txt |    1 +
 drivers/rtc/Kconfig                                |   11 +
 drivers/rtc/Makefile                               |    1 +
 drivers/rtc/rtc-snvs.c                             |  350 ++++++++++++++++++++
 5 files changed, 414 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/rtc/snvs-rtc.txt
 create mode 100644 drivers/rtc/rtc-snvs.c
Shawn Guo - July 13, 2012, 8:22 a.m.
Sorry for resending the patch.  For some reason, the patch did not
show up in my Linaro mailbox, and I thought it was failed to deliver.

Alessandro,

Is it possible to queue the patch for 3.6?

Regards,
Shawn


On Fri, Jul 13, 2012 at 03:31:03PM +0800, Shawn Guo wrote:
> Add an RTC driver for Freescale Secure Non-Volatile Storage (SNVS)
> Low Power (LP) RTC.
> 
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
> Cc: Alessandro Zummo <a.zummo@towertech.it>
> ---
> Changes since v2:
>  * Use SIMPLE_DEV_PM_OPS to save one #ifdef as suggested by Stephen
> 
>  .../devicetree/bindings/crypto/fsl-sec4.txt        |   51 +++
>  Documentation/devicetree/bindings/rtc/snvs-rtc.txt |    1 +
>  drivers/rtc/Kconfig                                |   11 +
>  drivers/rtc/Makefile                               |    1 +
>  drivers/rtc/rtc-snvs.c                             |  350 ++++++++++++++++++++
>  5 files changed, 414 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/rtc/snvs-rtc.txt
>  create mode 100644 drivers/rtc/rtc-snvs.c
> 
> diff --git a/Documentation/devicetree/bindings/crypto/fsl-sec4.txt b/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
> index bf57ecd..bd7ce12 100644
> --- a/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
> +++ b/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
> @@ -9,6 +9,7 @@ Copyright (C) 2008-2011 Freescale Semiconductor Inc.
>     -Run Time Integrity Check (RTIC) Node
>     -Run Time Integrity Check (RTIC) Memory Node
>     -Secure Non-Volatile Storage (SNVS) Node
> +   -Secure Non-Volatile Storage (SNVS) Low Power (LP) RTC Node
>     -Full Example
>  
>  NOTE: the SEC 4 is also known as Freescale's Cryptographic Accelerator
> @@ -294,6 +295,27 @@ Secure Non-Volatile Storage (SNVS) Node
>            address and length of the SEC4 configuration
>            registers.
>  
> +   - #address-cells
> +       Usage: required
> +       Value type: <u32>
> +       Definition: A standard property.  Defines the number of cells
> +           for representing physical addresses in child nodes.  Must
> +           have a value of 1.
> +
> +   - #size-cells
> +       Usage: required
> +       Value type: <u32>
> +       Definition: A standard property.  Defines the number of cells
> +           for representing the size of physical addresses in
> +           child nodes.  Must have a value of 1.
> +
> +   - ranges
> +       Usage: required
> +       Value type: <prop-encoded-array>
> +       Definition: A standard property.  Specifies the physical address
> +           range of the SNVS register space.  A triplet that includes
> +           the child address, parent address, & length.
> +
>     - interrupts
>        Usage: required
>        Value type: <prop_encoded-array>
> @@ -314,11 +336,34 @@ EXAMPLE
>  	sec_mon@314000 {
>  		compatible = "fsl,sec-v4.0-mon";
>  		reg = <0x314000 0x1000>;
> +		ranges = <0 0x314000 0x1000>;
>  		interrupt-parent = <&mpic>;
>  		interrupts = <93 2>;
>  	};
>  
>  =====================================================================
> +Secure Non-Volatile Storage (SNVS) Low Power (LP) RTC Node
> +
> +  A SNVS child node that defines SNVS LP RTC.
> +
> +  - compatible
> +      Usage: required
> +      Value type: <string>
> +      Definition: Must include "fsl,sec-v4.0-mon-rtc-lp".
> +
> +  - reg
> +      Usage: required
> +      Value type: <prop-encoded-array>
> +      Definition: A standard property.  Specifies the physical
> +          address and length of the SNVS LP configuration registers.
> +
> +EXAMPLE
> +	sec_mon_rtc_lp@314000 {
> +		compatible = "fsl,sec-v4.0-mon-rtc-lp";
> +		reg = <0x34 0x58>;
> +	};
> +
> +=====================================================================
>  FULL EXAMPLE
>  
>  	crypto: crypto@300000 {
> @@ -390,8 +435,14 @@ FULL EXAMPLE
>  	sec_mon: sec_mon@314000 {
>  		compatible = "fsl,sec-v4.0-mon";
>  		reg = <0x314000 0x1000>;
> +		ranges = <0 0x314000 0x1000>;
>  		interrupt-parent = <&mpic>;
>  		interrupts = <93 2>;
> +
> +		sec_mon_rtc_lp@34 {
> +			compatible = "fsl,sec-v4.0-mon-rtc-lp";
> +			reg = <0x34 0x58>;
> +		};
>  	};
>  
>  =====================================================================
> diff --git a/Documentation/devicetree/bindings/rtc/snvs-rtc.txt b/Documentation/devicetree/bindings/rtc/snvs-rtc.txt
> new file mode 100644
> index 0000000..fb61ed7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rtc/snvs-rtc.txt
> @@ -0,0 +1 @@
> +See Documentation/devicetree/bindings/crypto/fsl-sec4.txt for details.
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index 08cbdb9..e174e16 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -1087,4 +1087,15 @@ config RTC_DRV_MXC
>  	   This driver can also be built as a module, if so, the module
>  	   will be called "rtc-mxc".
>  
> +config RTC_DRV_SNVS
> +	tristate "Freescale SNVS RTC support"
> +	depends on HAS_IOMEM
> +	depends on OF
> +	help
> +	   If you say yes here you get support for the Freescale SNVS
> +	   Low Power (LP) RTC module.
> +
> +	   This driver can also be built as a module, if so, the module
> +	   will be called "rtc-snvs".
> +
>  endif # RTC_CLASS
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 2973921..0e3ff92 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -95,6 +95,7 @@ obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
>  obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
>  obj-$(CONFIG_RTC_DRV_SA1100)	+= rtc-sa1100.o
>  obj-$(CONFIG_RTC_DRV_SH)	+= rtc-sh.o
> +obj-$(CONFIG_RTC_DRV_SNVS)	+= rtc-snvs.o
>  obj-$(CONFIG_RTC_DRV_SPEAR)	+= rtc-spear.o
>  obj-$(CONFIG_RTC_DRV_STARFIRE)	+= rtc-starfire.o
>  obj-$(CONFIG_RTC_DRV_STK17TA8)	+= rtc-stk17ta8.o
> diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> new file mode 100644
> index 0000000..912f116
> --- /dev/null
> +++ b/drivers/rtc/rtc-snvs.c
> @@ -0,0 +1,350 @@
> +/*
> + * Copyright (C) 2011-2012 Freescale Semiconductor, Inc.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/rtc.h>
> +
> +/* These register offsets are relative to LP (Low Power) range */
> +#define SNVS_LPCR		0x04
> +#define SNVS_LPSR		0x18
> +#define SNVS_LPSRTCMR		0x1c
> +#define SNVS_LPSRTCLR		0x20
> +#define SNVS_LPTAR		0x24
> +#define SNVS_LPPGDR		0x30
> +
> +#define SNVS_LPCR_SRTC_ENV	(1 << 0)
> +#define SNVS_LPCR_LPTA_EN	(1 << 1)
> +#define SNVS_LPCR_LPWUI_EN	(1 << 3)
> +#define SNVS_LPSR_LPTA		(1 << 0)
> +
> +#define SNVS_LPPGDR_INIT	0x41736166
> +#define CNTR_TO_SECS_SH		15
> +
> +struct snvs_rtc_data {
> +	struct rtc_device *rtc;
> +	void __iomem *ioaddr;
> +	int irq;
> +	spinlock_t lock;
> +};
> +
> +static u32 rtc_read_lp_counter(void __iomem *ioaddr)
> +{
> +	u64 read1, read2;
> +
> +	do {
> +		read1 = readl(ioaddr + SNVS_LPSRTCMR);
> +		read1 <<= 32;
> +		read1 |= readl(ioaddr + SNVS_LPSRTCLR);
> +
> +		read2 = readl(ioaddr + SNVS_LPSRTCMR);
> +		read2 <<= 32;
> +		read2 |= readl(ioaddr + SNVS_LPSRTCLR);
> +	} while (read1 != read2);
> +
> +	/* Convert 47-bit counter to 32-bit raw second count */
> +	return (u32) (read1 >> CNTR_TO_SECS_SH);
> +}
> +
> +static void rtc_write_sync_lp(void __iomem *ioaddr)
> +{
> +	u32 count1, count2, count3;
> +	int i;
> +
> +	/* Wait for 3 CKIL cycles */
> +	for (i = 0; i < 3; i++) {
> +		do {
> +			count1 = readl(ioaddr + SNVS_LPSRTCLR);
> +			count2 = readl(ioaddr + SNVS_LPSRTCLR);
> +		} while (count1 != count2);
> +
> +		/* Now wait until counter value changes */
> +		do {
> +			do {
> +				count2 = readl(ioaddr + SNVS_LPSRTCLR);
> +				count3 = readl(ioaddr + SNVS_LPSRTCLR);
> +			} while (count2 != count3);
> +		} while (count3 == count1);
> +	}
> +}
> +
> +static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(1);
> +	unsigned long flags;
> +	u32 lpcr;
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> +	if (enable)
> +		lpcr |= SNVS_LPCR_SRTC_ENV;
> +	else
> +		lpcr &= ~SNVS_LPCR_SRTC_ENV;
> +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	while (1) {
> +		lpcr = readl(data->ioaddr + SNVS_LPCR);
> +
> +		if (enable) {
> +			if (lpcr & SNVS_LPCR_SRTC_ENV)
> +				break;
> +		} else {
> +			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> +				break;
> +		}
> +
> +		if (time_after(jiffies, timeout))
> +			return -ETIMEDOUT;
> +	}
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	unsigned long time = rtc_read_lp_counter(data->ioaddr);
> +
> +	rtc_time_to_tm(time, tm);
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_set_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	unsigned long time;
> +
> +	rtc_tm_to_time(tm, &time);
> +
> +	/* Disable RTC first */
> +	snvs_rtc_enable(data, false);
> +
> +	/* Write 32-bit time to 47-bit timer, leaving 15 LSBs blank */
> +	writel(time << CNTR_TO_SECS_SH, data->ioaddr + SNVS_LPSRTCLR);
> +	writel(time >> (32 - CNTR_TO_SECS_SH), data->ioaddr + SNVS_LPSRTCMR);
> +
> +	/* Enable RTC again */
> +	snvs_rtc_enable(data, true);
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	u32 lptar, lpsr;
> +
> +	lptar = readl(data->ioaddr + SNVS_LPTAR);
> +	rtc_time_to_tm(lptar, &alrm->time);
> +
> +	lpsr = readl(data->ioaddr + SNVS_LPSR);
> +	alrm->pending = (lpsr & SNVS_LPSR_LPTA) ? 1 : 0;
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	u32 lpcr;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> +	if (enable)
> +		lpcr |= (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +	else
> +		lpcr &= ~(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
> +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	rtc_write_sync_lp(data->ioaddr);
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	struct rtc_time *alrm_tm = &alrm->time;
> +	unsigned long time;
> +	unsigned long flags;
> +	u32 lpcr;
> +
> +	rtc_tm_to_time(alrm_tm, &time);
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	/* Have to clear LPTA_EN before programming new alarm time in LPTAR */
> +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> +	lpcr &= ~SNVS_LPCR_LPTA_EN;
> +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	writel(time, data->ioaddr + SNVS_LPTAR);
> +
> +	/* Clear alarm interrupt status bit */
> +	writel(SNVS_LPSR_LPTA, data->ioaddr + SNVS_LPSR);
> +
> +	return snvs_rtc_alarm_irq_enable(dev, alrm->enabled);
> +}
> +
> +static const struct rtc_class_ops snvs_rtc_ops = {
> +	.read_time = snvs_rtc_read_time,
> +	.set_time = snvs_rtc_set_time,
> +	.read_alarm = snvs_rtc_read_alarm,
> +	.set_alarm = snvs_rtc_set_alarm,
> +	.alarm_irq_enable = snvs_rtc_alarm_irq_enable,
> +};
> +
> +static irqreturn_t snvs_rtc_irq_handler(int irq, void *dev_id)
> +{
> +	struct device *dev = dev_id;
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	u32 lpsr;
> +	u32 events = 0;
> +
> +	lpsr = readl(data->ioaddr + SNVS_LPSR);
> +
> +	if (lpsr & SNVS_LPSR_LPTA) {
> +		events |= (RTC_AF | RTC_IRQF);
> +
> +		/* RTC alarm should be one-shot */
> +		snvs_rtc_alarm_irq_enable(dev, 0);
> +
> +		rtc_update_irq(data->rtc, 1, events);
> +	}
> +
> +	/* clear interrupt status */
> +	writel(lpsr, data->ioaddr + SNVS_LPSR);
> +
> +	return events ? IRQ_HANDLED : IRQ_NONE;
> +}
> +
> +static int __devinit snvs_rtc_probe(struct platform_device *pdev)
> +{
> +	struct snvs_rtc_data *data;
> +	struct resource *res;
> +	int ret;
> +
> +	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	data->ioaddr = devm_request_and_ioremap(&pdev->dev, res);
> +	if (!data->ioaddr)
> +		return -EADDRNOTAVAIL;
> +
> +	data->irq = platform_get_irq(pdev, 0);
> +	if (data->irq < 0)
> +		return data->irq;
> +
> +	platform_set_drvdata(pdev, data);
> +
> +	spin_lock_init(&data->lock);
> +
> +	/* Initialize glitch detect */
> +	writel(SNVS_LPPGDR_INIT, data->ioaddr + SNVS_LPPGDR);
> +
> +	/* Clear interrupt status */
> +	writel(0xffffffff, data->ioaddr + SNVS_LPSR);
> +
> +	/* Enable RTC */
> +	snvs_rtc_enable(data, true);
> +
> +	device_init_wakeup(&pdev->dev, true);
> +
> +	ret = devm_request_irq(&pdev->dev, data->irq, snvs_rtc_irq_handler,
> +			       IRQF_SHARED, "rtc alarm", &pdev->dev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
> +			data->irq, ret);
> +		return ret;
> +	}
> +
> +	data->rtc = rtc_device_register(pdev->name, &pdev->dev,
> +					&snvs_rtc_ops, THIS_MODULE);
> +	if (IS_ERR(data->rtc)) {
> +		ret = PTR_ERR(data->rtc);
> +		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int __devexit snvs_rtc_remove(struct platform_device *pdev)
> +{
> +	struct snvs_rtc_data *data = platform_get_drvdata(pdev);
> +
> +	rtc_device_unregister(data->rtc);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int snvs_rtc_suspend(struct device *dev)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +
> +	if (device_may_wakeup(dev))
> +		enable_irq_wake(data->irq);
> +
> +	return 0;
> +}
> +
> +static int snvs_rtc_resume(struct device *dev)
> +{
> +	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +
> +	if (device_may_wakeup(dev))
> +		disable_irq_wake(data->irq);
> +
> +	return 0;
> +}
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(snvs_rtc_pm_ops, snvs_rtc_suspend, snvs_rtc_resume);
> +
> +static const struct of_device_id __devinitconst snvs_dt_ids[] = {
> +	{ .compatible = "fsl,sec-v4.0-mon-rtc-lp", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, snvs_dt_ids);
> +
> +static struct platform_driver snvs_rtc_driver = {
> +	.driver = {
> +		.name	= "snvs_rtc",
> +		.owner	= THIS_MODULE,
> +		.pm	= &snvs_rtc_pm_ops,
> +		.of_match_table = snvs_dt_ids,
> +	},
> +	.probe		= snvs_rtc_probe,
> +	.remove		= __devexit_p(snvs_rtc_remove),
> +};
> +module_platform_driver(snvs_rtc_driver);
> +
> +MODULE_AUTHOR("Freescale Semiconductor, Inc.");
> +MODULE_DESCRIPTION("Freescale SNVS RTC Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.4.1
> 
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
Shawn Guo - July 30, 2012, 4:18 a.m.
On Fri, Jul 13, 2012 at 04:22:04PM +0800, Shawn Guo wrote:
> Alessandro,
> 
> Is it possible to queue the patch for 3.6?
> 
Hi Andrew,

It seems that you are collecting RTC patches?  Can you please have
a look at the patch and see if it's possible to send it for 3.6?
Andrew Morton - Aug. 15, 2012, 12:03 a.m.
On Fri, 13 Jul 2012 15:31:03 +0800
Shawn Guo <shawn.guo@linaro.org> wrote:

> +static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
> +{
> +	unsigned long timeout = jiffies + msecs_to_jiffies(1);
> +	unsigned long flags;
> +	u32 lpcr;
> +
> +	spin_lock_irqsave(&data->lock, flags);
> +
> +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> +	if (enable)
> +		lpcr |= SNVS_LPCR_SRTC_ENV;
> +	else
> +		lpcr &= ~SNVS_LPCR_SRTC_ENV;
> +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> +
> +	spin_unlock_irqrestore(&data->lock, flags);
> +
> +	while (1) {
> +		lpcr = readl(data->ioaddr + SNVS_LPCR);
> +
> +		if (enable) {
> +			if (lpcr & SNVS_LPCR_SRTC_ENV)
> +				break;
> +		} else {
> +			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> +				break;
> +		}
> +
> +		if (time_after(jiffies, timeout))
> +			return -ETIMEDOUT;
> +	}
> +
> +	return 0;
> +}

The timeout code here is fragile.  If acquiring the spinlock takes more
than a millisecond or if this thread gets interrupted or preempted then
we could easily execute that loop just a single time, and fail.

It would be better to retry a fixed number of times, say 1000?  That
would take around 1 millisecond, but might be overkill.
Shawn Guo - Aug. 15, 2012, 2:16 p.m.
Thanks for looking at the patch, Andrew.

On Tue, Aug 14, 2012 at 05:03:00PM -0700, Andrew Morton wrote:
> On Fri, 13 Jul 2012 15:31:03 +0800
> Shawn Guo <shawn.guo@linaro.org> wrote:
> 
> > +static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
> > +{
> > +	unsigned long timeout = jiffies + msecs_to_jiffies(1);
> > +	unsigned long flags;
> > +	u32 lpcr;
> > +
> > +	spin_lock_irqsave(&data->lock, flags);
> > +
> > +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> > +	if (enable)
> > +		lpcr |= SNVS_LPCR_SRTC_ENV;
> > +	else
> > +		lpcr &= ~SNVS_LPCR_SRTC_ENV;
> > +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> > +
> > +	spin_unlock_irqrestore(&data->lock, flags);
> > +
> > +	while (1) {
> > +		lpcr = readl(data->ioaddr + SNVS_LPCR);
> > +
> > +		if (enable) {
> > +			if (lpcr & SNVS_LPCR_SRTC_ENV)
> > +				break;
> > +		} else {
> > +			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> > +				break;
> > +		}
> > +
> > +		if (time_after(jiffies, timeout))
> > +			return -ETIMEDOUT;
> > +	}
> > +
> > +	return 0;
> > +}
> 
> The timeout code here is fragile.  If acquiring the spinlock takes more
> than a millisecond or if this thread gets interrupted or preempted then
> we could easily execute that loop just a single time, and fail.
> 
So what about moving the timeout initialization to right above the
while(1) loop?

> It would be better to retry a fixed number of times, say 1000?  That
> would take around 1 millisecond, but might be overkill.
> 
How long a 1000 times loop takes really depends on the cpu frequency,
right?

BTW, I have received the notification telling that the patch has been
applied on -mm tree.  So should I just send you an incremental patch
to address the comment?
Andrew Morton - Aug. 15, 2012, 8:32 p.m.
On Wed, 15 Aug 2012 22:16:10 +0800
Shawn Guo <shawn.guo@linaro.org> wrote:

> Thanks for looking at the patch, Andrew.
> 
> On Tue, Aug 14, 2012 at 05:03:00PM -0700, Andrew Morton wrote:
> > On Fri, 13 Jul 2012 15:31:03 +0800
> > Shawn Guo <shawn.guo@linaro.org> wrote:
> > 
> > > +static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
> > > +{
> > > +	unsigned long timeout = jiffies + msecs_to_jiffies(1);
> > > +	unsigned long flags;
> > > +	u32 lpcr;
> > > +
> > > +	spin_lock_irqsave(&data->lock, flags);
> > > +
> > > +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> > > +	if (enable)
> > > +		lpcr |= SNVS_LPCR_SRTC_ENV;
> > > +	else
> > > +		lpcr &= ~SNVS_LPCR_SRTC_ENV;
> > > +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> > > +
> > > +	spin_unlock_irqrestore(&data->lock, flags);
> > > +
> > > +	while (1) {
> > > +		lpcr = readl(data->ioaddr + SNVS_LPCR);
> > > +
> > > +		if (enable) {
> > > +			if (lpcr & SNVS_LPCR_SRTC_ENV)
> > > +				break;
> > > +		} else {
> > > +			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> > > +				break;
> > > +		}
> > > +
> > > +		if (time_after(jiffies, timeout))
> > > +			return -ETIMEDOUT;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > 
> > The timeout code here is fragile.  If acquiring the spinlock takes more
> > than a millisecond or if this thread gets interrupted or preempted then
> > we could easily execute that loop just a single time, and fail.
> > 
> So what about moving the timeout initialization to right above the
> while(1) loop?

It still has the same problem - a well-timed preemption would cause a
timeout.

> > It would be better to retry a fixed number of times, say 1000?  That
> > would take around 1 millisecond, but might be overkill.
> > 
> How long a 1000 times loop takes really depends on the cpu frequency,
> right?

No, it will depend on the preiod of that readl(), which typically takes
much much longer than a cpu cycle.  It depends a lot on the bus type
but I'd guess that the readl would take 100's of nanoseconds.  Thus we
can use the expected readl duration to control the timeout interval.

> BTW, I have received the notification telling that the patch has been
> applied on -mm tree.  So should I just send you an incremental patch
> to address the comment?

An incremental is nice, as it lets people see what changed.  A full
replacement is OK for me as well - I turn it into an incrememntal so
that I and others can review the change and I fold the two back
together again before sending the patch to someone else (in this case,
Linus).
Lothar Waßmann - Aug. 16, 2012, 8:08 a.m.
Hi,

Andrew Morton writes:
> On Wed, 15 Aug 2012 22:16:10 +0800
> Shawn Guo <shawn.guo@linaro.org> wrote:
> 
> > Thanks for looking at the patch, Andrew.
> > 
> > On Tue, Aug 14, 2012 at 05:03:00PM -0700, Andrew Morton wrote:
> > > On Fri, 13 Jul 2012 15:31:03 +0800
> > > Shawn Guo <shawn.guo@linaro.org> wrote:
> > > 
> > > > +static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
> > > > +{
> > > > +	unsigned long timeout = jiffies + msecs_to_jiffies(1);
> > > > +	unsigned long flags;
> > > > +	u32 lpcr;
> > > > +
> > > > +	spin_lock_irqsave(&data->lock, flags);
> > > > +
> > > > +	lpcr = readl(data->ioaddr + SNVS_LPCR);
> > > > +	if (enable)
> > > > +		lpcr |= SNVS_LPCR_SRTC_ENV;
> > > > +	else
> > > > +		lpcr &= ~SNVS_LPCR_SRTC_ENV;
> > > > +	writel(lpcr, data->ioaddr + SNVS_LPCR);
> > > > +
> > > > +	spin_unlock_irqrestore(&data->lock, flags);
> > > > +
> > > > +	while (1) {
> > > > +		lpcr = readl(data->ioaddr + SNVS_LPCR);
> > > > +
> > > > +		if (enable) {
> > > > +			if (lpcr & SNVS_LPCR_SRTC_ENV)
> > > > +				break;
> > > > +		} else {
> > > > +			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
> > > > +				break;
> > > > +		}
> > > > +
> > > > +		if (time_after(jiffies, timeout))
> > > > +			return -ETIMEDOUT;
> > > > +	}
> > > > +
> > > > +	return 0;
> > > > +}
> > > 
> > > The timeout code here is fragile.  If acquiring the spinlock takes more
> > > than a millisecond or if this thread gets interrupted or preempted then
> > > we could easily execute that loop just a single time, and fail.
> > > 
> > So what about moving the timeout initialization to right above the
> > while(1) loop?
> 
> It still has the same problem - a well-timed preemption would cause a
> timeout.
> 
> > > It would be better to retry a fixed number of times, say 1000?  That
> > > would take around 1 millisecond, but might be overkill.
> > > 
> > How long a 1000 times loop takes really depends on the cpu frequency,
> > right?
> 
> No, it will depend on the preiod of that readl(), which typically takes
> much much longer than a cpu cycle.  It depends a lot on the bus type
> but I'd guess that the readl would take 100's of nanoseconds.  Thus we
> can use the expected readl duration to control the timeout interval.
> 
Why not read the register once more in case of a timeout, which
would guarantee to have a current view of the register contents no
matter how long the process may have been descheduled before:

[...]
static int snvs_rtc_enable_done(int enable, void __iomem *addr)
{
	u32 lpcr = readl(addr + SNVS_LPCR);

	return !!enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
}
[...]
	while (1) {
		if (svns_rtc_enable_done(enable, data->ioaddr))
			break;

		if (time_after(jiffies, timeout)) {
			if (!svns_rtc_enable_done(enable, data->ioaddr))
				return -ETIMEDOUT;
		}
	}


Lothar Waßmann
Shawn Guo - Aug. 17, 2012, 6:14 a.m.
On Thu, Aug 16, 2012 at 10:08:04AM +0200, Lothar Waßmann wrote:
> Why not read the register once more in case of a timeout, which
> would guarantee to have a current view of the register contents no
> matter how long the process may have been descheduled before:
> 
> [...]
> static int snvs_rtc_enable_done(int enable, void __iomem *addr)
> {
> 	u32 lpcr = readl(addr + SNVS_LPCR);
> 
> 	return !!enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
> }
> [...]
> 	while (1) {
> 		if (svns_rtc_enable_done(enable, data->ioaddr))
> 			break;
> 
> 		if (time_after(jiffies, timeout)) {
> 			if (!svns_rtc_enable_done(enable, data->ioaddr))
> 				return -ETIMEDOUT;
> 		}
> 	}
> 
I'm fine with this solution.  Can you send a formal patch for this?
Then we will have two incremental patches (I already sent the fixed
times loop one) for Andrew to choose one.
Lothar Waßmann - Aug. 18, 2012, 6:43 a.m.
Hi,

Shawn Guo writes:
> On Thu, Aug 16, 2012 at 10:08:04AM +0200, Lothar Waßmann wrote:
> > Why not read the register once more in case of a timeout, which
> > would guarantee to have a current view of the register contents no
> > matter how long the process may have been descheduled before:
> > 
> > [...]
> > static int snvs_rtc_enable_done(int enable, void __iomem *addr)
> > {
> > 	u32 lpcr = readl(addr + SNVS_LPCR);
> > 
> > 	return !!enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
> > }
> > [...]
> > 	while (1) {
> > 		if (svns_rtc_enable_done(enable, data->ioaddr))
> > 			break;
> > 
> > 		if (time_after(jiffies, timeout)) {
> > 			if (!svns_rtc_enable_done(enable, data->ioaddr))
> > 				return -ETIMEDOUT;
> > 		}
> > 	}
> > 
> I'm fine with this solution.  Can you send a formal patch for this?
> Then we will have two incremental patches (I already sent the fixed
> times loop one) for Andrew to choose one.
> 
What should I base this patch on?


Lothar Waßmann
Shawn Guo - Aug. 18, 2012, 7:03 a.m.
On Sat, Aug 18, 2012 at 08:43:04AM +0200, Lothar Waßmann wrote:
> Hi,
> 
> Shawn Guo writes:
> > On Thu, Aug 16, 2012 at 10:08:04AM +0200, Lothar Waßmann wrote:
> > > Why not read the register once more in case of a timeout, which
> > > would guarantee to have a current view of the register contents no
> > > matter how long the process may have been descheduled before:
> > > 
> > > [...]
> > > static int snvs_rtc_enable_done(int enable, void __iomem *addr)
> > > {
> > > 	u32 lpcr = readl(addr + SNVS_LPCR);
> > > 
> > > 	return !!enable ^ !(lpcr & SNVS_LPCR_SRTC_ENV);
> > > }
> > > [...]
> > > 	while (1) {
> > > 		if (svns_rtc_enable_done(enable, data->ioaddr))
> > > 			break;
> > > 
> > > 		if (time_after(jiffies, timeout)) {
> > > 			if (!svns_rtc_enable_done(enable, data->ioaddr))
> > > 				return -ETIMEDOUT;
> > > 		}
> > > 	}
> > > 
> > I'm fine with this solution.  Can you send a formal patch for this?
> > Then we will have two incremental patches (I already sent the fixed
> > times loop one) for Andrew to choose one.
> > 
> What should I base this patch on?
> 
v3.6-rc1 with "[PATCH v3] rtc: snvs: add Freescale rtc-snvs driver"
applied.

Patch

diff --git a/Documentation/devicetree/bindings/crypto/fsl-sec4.txt b/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
index bf57ecd..bd7ce12 100644
--- a/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
+++ b/Documentation/devicetree/bindings/crypto/fsl-sec4.txt
@@ -9,6 +9,7 @@  Copyright (C) 2008-2011 Freescale Semiconductor Inc.
    -Run Time Integrity Check (RTIC) Node
    -Run Time Integrity Check (RTIC) Memory Node
    -Secure Non-Volatile Storage (SNVS) Node
+   -Secure Non-Volatile Storage (SNVS) Low Power (LP) RTC Node
    -Full Example
 
 NOTE: the SEC 4 is also known as Freescale's Cryptographic Accelerator
@@ -294,6 +295,27 @@  Secure Non-Volatile Storage (SNVS) Node
           address and length of the SEC4 configuration
           registers.
 
+   - #address-cells
+       Usage: required
+       Value type: <u32>
+       Definition: A standard property.  Defines the number of cells
+           for representing physical addresses in child nodes.  Must
+           have a value of 1.
+
+   - #size-cells
+       Usage: required
+       Value type: <u32>
+       Definition: A standard property.  Defines the number of cells
+           for representing the size of physical addresses in
+           child nodes.  Must have a value of 1.
+
+   - ranges
+       Usage: required
+       Value type: <prop-encoded-array>
+       Definition: A standard property.  Specifies the physical address
+           range of the SNVS register space.  A triplet that includes
+           the child address, parent address, & length.
+
    - interrupts
       Usage: required
       Value type: <prop_encoded-array>
@@ -314,11 +336,34 @@  EXAMPLE
 	sec_mon@314000 {
 		compatible = "fsl,sec-v4.0-mon";
 		reg = <0x314000 0x1000>;
+		ranges = <0 0x314000 0x1000>;
 		interrupt-parent = <&mpic>;
 		interrupts = <93 2>;
 	};
 
 =====================================================================
+Secure Non-Volatile Storage (SNVS) Low Power (LP) RTC Node
+
+  A SNVS child node that defines SNVS LP RTC.
+
+  - compatible
+      Usage: required
+      Value type: <string>
+      Definition: Must include "fsl,sec-v4.0-mon-rtc-lp".
+
+  - reg
+      Usage: required
+      Value type: <prop-encoded-array>
+      Definition: A standard property.  Specifies the physical
+          address and length of the SNVS LP configuration registers.
+
+EXAMPLE
+	sec_mon_rtc_lp@314000 {
+		compatible = "fsl,sec-v4.0-mon-rtc-lp";
+		reg = <0x34 0x58>;
+	};
+
+=====================================================================
 FULL EXAMPLE
 
 	crypto: crypto@300000 {
@@ -390,8 +435,14 @@  FULL EXAMPLE
 	sec_mon: sec_mon@314000 {
 		compatible = "fsl,sec-v4.0-mon";
 		reg = <0x314000 0x1000>;
+		ranges = <0 0x314000 0x1000>;
 		interrupt-parent = <&mpic>;
 		interrupts = <93 2>;
+
+		sec_mon_rtc_lp@34 {
+			compatible = "fsl,sec-v4.0-mon-rtc-lp";
+			reg = <0x34 0x58>;
+		};
 	};
 
 =====================================================================
diff --git a/Documentation/devicetree/bindings/rtc/snvs-rtc.txt b/Documentation/devicetree/bindings/rtc/snvs-rtc.txt
new file mode 100644
index 0000000..fb61ed7
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/snvs-rtc.txt
@@ -0,0 +1 @@ 
+See Documentation/devicetree/bindings/crypto/fsl-sec4.txt for details.
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 08cbdb9..e174e16 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1087,4 +1087,15 @@  config RTC_DRV_MXC
 	   This driver can also be built as a module, if so, the module
 	   will be called "rtc-mxc".
 
+config RTC_DRV_SNVS
+	tristate "Freescale SNVS RTC support"
+	depends on HAS_IOMEM
+	depends on OF
+	help
+	   If you say yes here you get support for the Freescale SNVS
+	   Low Power (LP) RTC module.
+
+	   This driver can also be built as a module, if so, the module
+	   will be called "rtc-snvs".
+
 endif # RTC_CLASS
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 2973921..0e3ff92 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -95,6 +95,7 @@  obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
 obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
 obj-$(CONFIG_RTC_DRV_SA1100)	+= rtc-sa1100.o
 obj-$(CONFIG_RTC_DRV_SH)	+= rtc-sh.o
+obj-$(CONFIG_RTC_DRV_SNVS)	+= rtc-snvs.o
 obj-$(CONFIG_RTC_DRV_SPEAR)	+= rtc-spear.o
 obj-$(CONFIG_RTC_DRV_STARFIRE)	+= rtc-starfire.o
 obj-$(CONFIG_RTC_DRV_STK17TA8)	+= rtc-stk17ta8.o
diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
new file mode 100644
index 0000000..912f116
--- /dev/null
+++ b/drivers/rtc/rtc-snvs.c
@@ -0,0 +1,350 @@ 
+/*
+ * Copyright (C) 2011-2012 Freescale Semiconductor, Inc.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+/* These register offsets are relative to LP (Low Power) range */
+#define SNVS_LPCR		0x04
+#define SNVS_LPSR		0x18
+#define SNVS_LPSRTCMR		0x1c
+#define SNVS_LPSRTCLR		0x20
+#define SNVS_LPTAR		0x24
+#define SNVS_LPPGDR		0x30
+
+#define SNVS_LPCR_SRTC_ENV	(1 << 0)
+#define SNVS_LPCR_LPTA_EN	(1 << 1)
+#define SNVS_LPCR_LPWUI_EN	(1 << 3)
+#define SNVS_LPSR_LPTA		(1 << 0)
+
+#define SNVS_LPPGDR_INIT	0x41736166
+#define CNTR_TO_SECS_SH		15
+
+struct snvs_rtc_data {
+	struct rtc_device *rtc;
+	void __iomem *ioaddr;
+	int irq;
+	spinlock_t lock;
+};
+
+static u32 rtc_read_lp_counter(void __iomem *ioaddr)
+{
+	u64 read1, read2;
+
+	do {
+		read1 = readl(ioaddr + SNVS_LPSRTCMR);
+		read1 <<= 32;
+		read1 |= readl(ioaddr + SNVS_LPSRTCLR);
+
+		read2 = readl(ioaddr + SNVS_LPSRTCMR);
+		read2 <<= 32;
+		read2 |= readl(ioaddr + SNVS_LPSRTCLR);
+	} while (read1 != read2);
+
+	/* Convert 47-bit counter to 32-bit raw second count */
+	return (u32) (read1 >> CNTR_TO_SECS_SH);
+}
+
+static void rtc_write_sync_lp(void __iomem *ioaddr)
+{
+	u32 count1, count2, count3;
+	int i;
+
+	/* Wait for 3 CKIL cycles */
+	for (i = 0; i < 3; i++) {
+		do {
+			count1 = readl(ioaddr + SNVS_LPSRTCLR);
+			count2 = readl(ioaddr + SNVS_LPSRTCLR);
+		} while (count1 != count2);
+
+		/* Now wait until counter value changes */
+		do {
+			do {
+				count2 = readl(ioaddr + SNVS_LPSRTCLR);
+				count3 = readl(ioaddr + SNVS_LPSRTCLR);
+			} while (count2 != count3);
+		} while (count3 == count1);
+	}
+}
+
+static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(1);
+	unsigned long flags;
+	u32 lpcr;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	lpcr = readl(data->ioaddr + SNVS_LPCR);
+	if (enable)
+		lpcr |= SNVS_LPCR_SRTC_ENV;
+	else
+		lpcr &= ~SNVS_LPCR_SRTC_ENV;
+	writel(lpcr, data->ioaddr + SNVS_LPCR);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	while (1) {
+		lpcr = readl(data->ioaddr + SNVS_LPCR);
+
+		if (enable) {
+			if (lpcr & SNVS_LPCR_SRTC_ENV)
+				break;
+		} else {
+			if (!(lpcr & SNVS_LPCR_SRTC_ENV))
+				break;
+		}
+
+		if (time_after(jiffies, timeout))
+			return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static int snvs_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	unsigned long time = rtc_read_lp_counter(data->ioaddr);
+
+	rtc_time_to_tm(time, tm);
+
+	return 0;
+}
+
+static int snvs_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	unsigned long time;
+
+	rtc_tm_to_time(tm, &time);
+
+	/* Disable RTC first */
+	snvs_rtc_enable(data, false);
+
+	/* Write 32-bit time to 47-bit timer, leaving 15 LSBs blank */
+	writel(time << CNTR_TO_SECS_SH, data->ioaddr + SNVS_LPSRTCLR);
+	writel(time >> (32 - CNTR_TO_SECS_SH), data->ioaddr + SNVS_LPSRTCMR);
+
+	/* Enable RTC again */
+	snvs_rtc_enable(data, true);
+
+	return 0;
+}
+
+static int snvs_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	u32 lptar, lpsr;
+
+	lptar = readl(data->ioaddr + SNVS_LPTAR);
+	rtc_time_to_tm(lptar, &alrm->time);
+
+	lpsr = readl(data->ioaddr + SNVS_LPSR);
+	alrm->pending = (lpsr & SNVS_LPSR_LPTA) ? 1 : 0;
+
+	return 0;
+}
+
+static int snvs_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	u32 lpcr;
+	unsigned long flags;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	lpcr = readl(data->ioaddr + SNVS_LPCR);
+	if (enable)
+		lpcr |= (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
+	else
+		lpcr &= ~(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN);
+	writel(lpcr, data->ioaddr + SNVS_LPCR);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	rtc_write_sync_lp(data->ioaddr);
+
+	return 0;
+}
+
+static int snvs_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	struct rtc_time *alrm_tm = &alrm->time;
+	unsigned long time;
+	unsigned long flags;
+	u32 lpcr;
+
+	rtc_tm_to_time(alrm_tm, &time);
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	/* Have to clear LPTA_EN before programming new alarm time in LPTAR */
+	lpcr = readl(data->ioaddr + SNVS_LPCR);
+	lpcr &= ~SNVS_LPCR_LPTA_EN;
+	writel(lpcr, data->ioaddr + SNVS_LPCR);
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	writel(time, data->ioaddr + SNVS_LPTAR);
+
+	/* Clear alarm interrupt status bit */
+	writel(SNVS_LPSR_LPTA, data->ioaddr + SNVS_LPSR);
+
+	return snvs_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+static const struct rtc_class_ops snvs_rtc_ops = {
+	.read_time = snvs_rtc_read_time,
+	.set_time = snvs_rtc_set_time,
+	.read_alarm = snvs_rtc_read_alarm,
+	.set_alarm = snvs_rtc_set_alarm,
+	.alarm_irq_enable = snvs_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t snvs_rtc_irq_handler(int irq, void *dev_id)
+{
+	struct device *dev = dev_id;
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	u32 lpsr;
+	u32 events = 0;
+
+	lpsr = readl(data->ioaddr + SNVS_LPSR);
+
+	if (lpsr & SNVS_LPSR_LPTA) {
+		events |= (RTC_AF | RTC_IRQF);
+
+		/* RTC alarm should be one-shot */
+		snvs_rtc_alarm_irq_enable(dev, 0);
+
+		rtc_update_irq(data->rtc, 1, events);
+	}
+
+	/* clear interrupt status */
+	writel(lpsr, data->ioaddr + SNVS_LPSR);
+
+	return events ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static int __devinit snvs_rtc_probe(struct platform_device *pdev)
+{
+	struct snvs_rtc_data *data;
+	struct resource *res;
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->ioaddr = devm_request_and_ioremap(&pdev->dev, res);
+	if (!data->ioaddr)
+		return -EADDRNOTAVAIL;
+
+	data->irq = platform_get_irq(pdev, 0);
+	if (data->irq < 0)
+		return data->irq;
+
+	platform_set_drvdata(pdev, data);
+
+	spin_lock_init(&data->lock);
+
+	/* Initialize glitch detect */
+	writel(SNVS_LPPGDR_INIT, data->ioaddr + SNVS_LPPGDR);
+
+	/* Clear interrupt status */
+	writel(0xffffffff, data->ioaddr + SNVS_LPSR);
+
+	/* Enable RTC */
+	snvs_rtc_enable(data, true);
+
+	device_init_wakeup(&pdev->dev, true);
+
+	ret = devm_request_irq(&pdev->dev, data->irq, snvs_rtc_irq_handler,
+			       IRQF_SHARED, "rtc alarm", &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
+			data->irq, ret);
+		return ret;
+	}
+
+	data->rtc = rtc_device_register(pdev->name, &pdev->dev,
+					&snvs_rtc_ops, THIS_MODULE);
+	if (IS_ERR(data->rtc)) {
+		ret = PTR_ERR(data->rtc);
+		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int __devexit snvs_rtc_remove(struct platform_device *pdev)
+{
+	struct snvs_rtc_data *data = platform_get_drvdata(pdev);
+
+	rtc_device_unregister(data->rtc);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int snvs_rtc_suspend(struct device *dev)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(data->irq);
+
+	return 0;
+}
+
+static int snvs_rtc_resume(struct device *dev)
+{
+	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(data->irq);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(snvs_rtc_pm_ops, snvs_rtc_suspend, snvs_rtc_resume);
+
+static const struct of_device_id __devinitconst snvs_dt_ids[] = {
+	{ .compatible = "fsl,sec-v4.0-mon-rtc-lp", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, snvs_dt_ids);
+
+static struct platform_driver snvs_rtc_driver = {
+	.driver = {
+		.name	= "snvs_rtc",
+		.owner	= THIS_MODULE,
+		.pm	= &snvs_rtc_pm_ops,
+		.of_match_table = snvs_dt_ids,
+	},
+	.probe		= snvs_rtc_probe,
+	.remove		= __devexit_p(snvs_rtc_remove),
+};
+module_platform_driver(snvs_rtc_driver);
+
+MODULE_AUTHOR("Freescale Semiconductor, Inc.");
+MODULE_DESCRIPTION("Freescale SNVS RTC Driver");
+MODULE_LICENSE("GPL");