[v3,1/2] GPIO: add single-register GPIO via CREG driver

Add single-register MMIO GPIO driver for complex cases where
only several fields in register belong to GPIO lines and each GPIO
line owns a field with different length and on/off value.

Such CREG GPIOs are used in Synopsys AXS10x and HSDK boards.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
Changes v2->v3:
 * Move parameters into a lookup table instead of device tree.
 * Use the ngpios attribute for instead of snps,ngpios.

 MAINTAINERS                   |   6 ++
 drivers/gpio/Kconfig          |  10 ++
 drivers/gpio/Makefile         |   1 +
 drivers/gpio/gpio-creg-snps.c | 212 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 229 insertions(+)
 create mode 100644 drivers/gpio/gpio-creg-snps.c

Hi Linus,

Maybe you have any comments or remarks about this patch? And if you don't could you please apply it.
Thanks!

On Tue, 2018-09-11 at 18:09 +0300, Eugeniy Paltsev wrote:
> Add single-register MMIO GPIO driver for complex cases where
> only several fields in register belong to GPIO lines and each GPIO
> line owns a field with different length and on/off value.
> 
> Such CREG GPIOs are used in Synopsys AXS10x and HSDK boards.
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
> Changes v2->v3:
>  * Move parameters into a lookup table instead of device tree.
>  * Use the ngpios attribute for instead of snps,ngpios.
> 
>  MAINTAINERS                   |   6 ++
>  drivers/gpio/Kconfig          |  10 ++
>  drivers/gpio/Makefile         |   1 +
>  drivers/gpio/gpio-creg-snps.c | 212 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 229 insertions(+)
>  create mode 100644 drivers/gpio/gpio-creg-snps.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 544cac829cf4..e731f2f9648a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13734,6 +13734,12 @@ S:	Supported
>  F:	drivers/reset/reset-axs10x.c
>  F:	Documentation/devicetree/bindings/reset/snps,axs10x-reset.txt
>  
> +SYNOPSYS CREG GPIO DRIVER
> +M:	Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> +S:	Maintained
> +F:	drivers/gpio/gpio-creg-snps.c
> +F:	Documentation/devicetree/bindings/gpio/snps,creg-gpio.txt
> +
>  SYNOPSYS DESIGNWARE 8250 UART DRIVER
>  R:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>  S:	Maintained
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 71c0ab46f216..78155ac22b0c 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -430,6 +430,16 @@ config GPIO_REG
>  	  A 32-bit single register GPIO fixed in/out implementation.  This
>  	  can be used to represent any register as a set of GPIO signals.
>  
> +config GPIO_SNPS_CREG
> +	bool "Synopsys GPIO via CREG (Control REGisters) driver"
> +	depends on ARC || COMPILE_TEST
> +	select OF_GPIO
> +	help
> +	  This driver supports GPIOs via CREG on various Synopsys SoCs.
> +	  This is a single-register MMIO GPIO driver for complex cases
> +	  where only several fields in register belong to GPIO lines and
> +	  each GPIO line owns a field with different length and on/off value.
> +
>  config GPIO_SPEAR_SPICS
>  	bool "ST SPEAr13xx SPI Chip Select as GPIO support"
>  	depends on PLAT_SPEAR
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index 1324c8f966a7..993f8ad54a19 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -109,6 +109,7 @@ obj-$(CONFIG_GPIO_REG)		+= gpio-reg.o
>  obj-$(CONFIG_ARCH_SA1100)	+= gpio-sa1100.o
>  obj-$(CONFIG_GPIO_SCH)		+= gpio-sch.o
>  obj-$(CONFIG_GPIO_SCH311X)	+= gpio-sch311x.o
> +obj-$(CONFIG_GPIO_SNPS_CREG)	+= gpio-creg-snps.o
>  obj-$(CONFIG_GPIO_SODAVILLE)	+= gpio-sodaville.o
>  obj-$(CONFIG_GPIO_SPEAR_SPICS)	+= gpio-spear-spics.o
>  obj-$(CONFIG_GPIO_SPRD)		+= gpio-sprd.o
> diff --git a/drivers/gpio/gpio-creg-snps.c b/drivers/gpio/gpio-creg-snps.c
> new file mode 100644
> index 000000000000..2400dec529b2
> --- /dev/null
> +++ b/drivers/gpio/gpio-creg-snps.c
> @@ -0,0 +1,212 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// Synopsys CREG (Control REGisters) GPIO driver
> +//
> +// Copyright (C) 2018 Synopsys
> +// Author: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> +
> +#include <linux/of.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/of_gpio.h>
> +#include <linux/io.h>
> +#include <linux/of_platform.h>
> +#include <linux/module.h>
> +
> +#include "gpiolib.h"
> +
> +#define MAX_GPIO	32
> +
> +struct creg_layout {
> +	u8 ngpio;
> +	u8 shift[MAX_GPIO];
> +	u8 on[MAX_GPIO];
> +	u8 off[MAX_GPIO];
> +	u8 bit_per_gpio[MAX_GPIO];
> +};
> +
> +struct creg_gpio {
> +	struct of_mm_gpio_chip mmchip;
> +	spinlock_t lock;
> +	const struct creg_layout *layout;
> +};
> +
> +static void creg_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
> +{
> +	struct creg_gpio *hcg = gpiochip_get_data(gc);
> +	const struct creg_layout *layout = hcg->layout;
> +	u32 reg, reg_shift, value;
> +	unsigned long flags;
> +	int i;
> +
> +	value = val ? hcg->layout->on[gpio] : hcg->layout->off[gpio];
> +
> +	reg_shift = layout->shift[gpio];
> +	for (i = 0; i < gpio; i++)
> +		reg_shift += layout->bit_per_gpio[i] + layout->shift[i];
> +
> +	spin_lock_irqsave(&hcg->lock, flags);
> +	reg = readl(hcg->mmchip.regs);
> +	reg &= ~(GENMASK(layout->bit_per_gpio[i] - 1, 0) << reg_shift);
> +	reg |=  (value << reg_shift);
> +	writel(reg, hcg->mmchip.regs);
> +	spin_unlock_irqrestore(&hcg->lock, flags);
> +}
> +
> +static int creg_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
> +{
> +	creg_gpio_set(gc, gpio, val);
> +
> +	return 0;
> +}
> +
> +static int creg_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> +	return 0; /* output */
> +}
> +
> +static int creg_gpio_xlate(struct gpio_chip *gc,
> +			   const struct of_phandle_args *gpiospec, u32 *flags)
> +{
> +	if (gpiospec->args_count != 1) {
> +		dev_err(&gc->gpiodev->dev, "invalid args_count: %d\n",
> +			gpiospec->args_count);
> +		return -EINVAL;
> +	}
> +
> +	if (gpiospec->args[0] >= gc->ngpio) {
> +		dev_err(&gc->gpiodev->dev, "gpio number is too big: %d\n",
> +			gpiospec->args[0]);
> +		return -EINVAL;
> +	}
> +
> +	return gpiospec->args[0];
> +}
> +
> +static int creg_gpio_validate_pg(struct device *dev, struct creg_gpio *hcg,
> +				 int i)
> +{
> +	const struct creg_layout *layout = hcg->layout;
> +
> +	if (layout->bit_per_gpio[i] < 1 || layout->bit_per_gpio[i] > 8)
> +		return -EINVAL;
> +
> +	/* Check that on valiue suits it's placeholder */
> +	if (GENMASK(31, layout->bit_per_gpio[i]) & layout->on[i])
> +		return -EINVAL;
> +
> +	/* Check that off valiue suits it's placeholder */
> +	if (GENMASK(31, layout->bit_per_gpio[i]) & layout->off[i])
> +		return -EINVAL;
> +
> +	if (layout->on[i] == layout->off[i])
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int creg_gpio_validate(struct device *dev, struct creg_gpio *hcg,
> +			      u32 ngpios)
> +{
> +	u32 reg_len = 0;
> +	int i;
> +
> +	if (hcg->layout->ngpio < 1 || hcg->layout->ngpio > MAX_GPIO)
> +		return -EINVAL;
> +
> +	if (ngpios < 1 || ngpios > hcg->layout->ngpio) {
> +		dev_err(dev, "ngpios must be in [1:%u]\n", hcg->layout->ngpio);
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i < hcg->layout->ngpio; i++) {
> +		if (creg_gpio_validate_pg(dev, hcg, i))
> +			return -EINVAL;
> +
> +		reg_len += hcg->layout->shift[i] + hcg->layout->bit_per_gpio[i];
> +	}
> +
> +	/* Check that we suit in 32 bit register */
> +	if (reg_len > 32)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static const struct creg_layout hsdk_cs_ctl = {
> +	.ngpio		= 10,
> +	.shift		= { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
> +	.off		= { 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 },
> +	.on		= { 3, 3, 3, 3, 3, 3, 3, 3, 3, 3 },
> +	.bit_per_gpio	= { 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 }
> +};
> +
> +static const struct creg_layout axs10x_flsh_cs_ctl = {
> +	.ngpio		= 1,
> +	.shift		= { 0 },
> +	.off		= { 1 },
> +	.on		= { 3 },
> +	.bit_per_gpio	= { 2 }
> +};
> +
> +static const struct of_device_id creg_gpio_ids[] = {
> +	{
> +		.compatible = "snps,creg-gpio-axs10x",
> +		.data = &axs10x_flsh_cs_ctl
> +	}, {
> +		.compatible = "snps,creg-gpio-hsdk",
> +		.data = &hsdk_cs_ctl
> +	}, { /* sentinel */ }
> +};
> +
> +static int creg_gpio_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *match;
> +	struct device *dev = &pdev->dev;
> +	struct creg_gpio *hcg;
> +	u32 ngpios;
> +	int ret;
> +
> +	hcg = devm_kzalloc(dev, sizeof(struct creg_gpio), GFP_KERNEL);
> +	if (!hcg)
> +		return -ENOMEM;
> +
> +	match = of_match_node(creg_gpio_ids, pdev->dev.of_node);
> +	hcg->layout = match->data;
> +	if (!hcg->layout)
> +		return -EINVAL;
> +
> +	ret = of_property_read_u32(dev->of_node, "ngpios", &ngpios);
> +	if (ret)
> +		return ret;
> +
> +	ret = creg_gpio_validate(dev, hcg, ngpios);
> +	if (ret)
> +		return ret;
> +
> +	spin_lock_init(&hcg->lock);
> +
> +	hcg->mmchip.gc.ngpio = ngpios;
> +	hcg->mmchip.gc.set = creg_gpio_set;
> +	hcg->mmchip.gc.get_direction = creg_gpio_get_direction;
> +	hcg->mmchip.gc.direction_output = creg_gpio_dir_out;
> +	hcg->mmchip.gc.of_xlate = creg_gpio_xlate;
> +	hcg->mmchip.gc.of_gpio_n_cells = 1;
> +
> +	ret = of_mm_gpiochip_add_data(pdev->dev.of_node, &hcg->mmchip, hcg);
> +	if (ret)
> +		return ret;
> +
> +	dev_info(dev, "GPIO controller with %d gpios probed\n", ngpios);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver creg_gpio_snps_driver = {
> +	.driver = {
> +		.name = "snps-creg-gpio",
> +		.of_match_table = creg_gpio_ids,
> +	},
> +	.probe  = creg_gpio_probe,
> +};
> +builtin_platform_driver(creg_gpio_snps_driver);

Hi Eugeniy,

sorry for the delay, the driver is different from what I'm
used to so I needed focuses attention and it took some time.

On Tue, Sep 11, 2018 at 5:09 PM Eugeniy Paltsev
<Eugeniy.Paltsev@synopsys.com> wrote:

> Add single-register MMIO GPIO driver for complex cases where
> only several fields in register belong to GPIO lines and each GPIO
> line owns a field with different length and on/off value.
>
> Such CREG GPIOs are used in Synopsys AXS10x and HSDK boards.
>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> ---
> Changes v2->v3:
>  * Move parameters into a lookup table instead of device tree.
>  * Use the ngpios attribute for instead of snps,ngpios.

This is looking good! Just a few small things I want you to fix
(we can certainly queue this for the next kernel):

> +#include <linux/of.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/of_gpio.h>

Replace this with:
#include <linux/gpio/driver.h>

Drivers should only need to include that file. (Also move away from
mm_gpio_chip as per below.)

> +#include "gpiolib.h"

Why?

> +struct creg_gpio {
> +       struct of_mm_gpio_chip mmchip;

I would prefer to move away from using this. Just create a regular driver
please. Just struct gpio_chip and add a member
void __iomem *base; instead of referring to mmchip.regs.

In fact I want to rewrite all mm_gpio_chips but I just haven't had time.

> +static void creg_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)

Please rename the variable "gpio" to "offset".

This is clearer because "gpio" becomes quite ambigous.

> +static int creg_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
> +{
> +       return 0; /* output */
> +}

I think with the recent code changes in gpiolib you do not need to define
this function at all.
https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git/commit/?h=devel&id=ae9847f48a4b4bff0335da20be63ac84d94eb54c

> +static int creg_gpio_xlate(struct gpio_chip *gc,
> +                          const struct of_phandle_args *gpiospec, u32 *flags)
> +{
> +       if (gpiospec->args_count != 1) {
> +               dev_err(&gc->gpiodev->dev, "invalid args_count: %d\n",
> +                       gpiospec->args_count);
> +               return -EINVAL;
> +       }
> +
> +       if (gpiospec->args[0] >= gc->ngpio) {
> +               dev_err(&gc->gpiodev->dev, "gpio number is too big: %d\n",
> +                       gpiospec->args[0]);
> +               return -EINVAL;
> +       }
> +
> +       return gpiospec->args[0];
> +}

Another reason to not use mm_gpio_chip: just rely on standard twocell
translation and you can delete this.

> +       /* Check that we suit in 32 bit register */

s/suit/fit

Yours,
Linus Walleij