[PATCH] gpio: samsung: add devicetree init for s3c24xx arches

[Thomas Abraham]

Hi Heiko,

On 26 August 2012 03:23, Heiko Stübner <heiko at sntech.de> wrote:
> Until now the Exynos-SoC was the only Samsung-SoC supporting the GPIOs
> via the device tree. This patch implements dt-support for the
> s3c24xx arches.
>
> The controllers contain only 3 cells, as the underlying gpio controller
> does not support controlling the drive strength on a gpio level.
>
> Tested with the gpio-keys driver on a s3c2416 based machine.
>
> Signed-off-by: Heiko Stuebner <heiko at sntech.de>
> ---
>  .../devicetree/bindings/gpio/gpio-samsung.txt      |   38 ++++++++++++
>  drivers/gpio/gpio-samsung.c                        |   63 ++++++++++++++++++++
>  2 files changed, 101 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-samsung.txt b/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
> index 5375625..ce6a7d4 100644
> --- a/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
> +++ b/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
> @@ -39,3 +39,41 @@ Example:
>                 #gpio-cells = <4>;
>                 gpio-controller;
>         };
> +
> +
> +Samsung S3C24XX GPIO Controller
> +
> +Required properties:
> +- compatible: Compatible property value should be "samsung,s3c24xx-gpio".

This is debatable, but I would choose to be specific here and use
"samsing,s3c2416-gpio". For instance, SoC's in s3c24xx family have
differing value for pull none/down/up.

> +
> +- reg: Physical base address of the controller and length of memory mapped
> +  region.
> +
> +- #gpio-cells: Should be 3. The syntax of the gpio specifier used by client nodes
> +  should be the following with values derived from the SoC user manual.
> +     <[phandle of the gpio controller node]
> +      [pin number within the gpio controller]
> +      [mux function]
> +      [flags and pull up/down]
> +
> +  Values for gpio specifier:
> +  - Pin number: depending on the controller a number from 0 up to 15.
> +  - Flags and Pull Up/Down: 0 - Pull Up/Down Disabled.
> +                            1 - Pull Down Enabled.
> +                            3 - Pull Up Enabled.

As per s3c2416 user manual, 2 is used for Pull Up and 3 is listed as
reserved value. Any particular reason to use 3 here for pull up and
not 2 as per the user manual?

> +          Bit 16 (0x00010000) - Input is active low.
> +
> +- gpio-controller: Specifies that the node is a gpio controller.
> +- #address-cells: should be 1.
> +- #size-cells: should be 1.

It would be informative to add information about the 'mux function'
cell here as well. Specifically, on how to handle the banks that have
an extended GPxSEL register that allow additional pin function
selection.

> +
> +Example:
> +
> +       gpa: gpio-controller at 56000000 {
> +               #address-cells = <1>;
> +               #size-cells = <1>;
> +               compatible = "samsung,s3c24xx-gpio";
> +               reg = <0x56000000 0x10>;
> +               #gpio-cells = <3>;
> +               gpio-controller;
> +       };
> diff --git a/drivers/gpio/gpio-samsung.c b/drivers/gpio/gpio-samsung.c
> index a150d2e..80a2817 100644
> --- a/drivers/gpio/gpio-samsung.c
> +++ b/drivers/gpio/gpio-samsung.c
> @@ -938,6 +938,67 @@ static void __init samsung_gpiolib_add(struct samsung_gpio_chip *chip)
>                 s3c_gpiolib_track(chip);
>  }
>
> +#if defined(CONFIG_PLAT_S3C24XX) && defined(CONFIG_OF)
> +static int s3c24xx_gpio_xlate(struct gpio_chip *gc,
> +                       const struct of_phandle_args *gpiospec, u32 *flags)
> +{
> +       unsigned int pin;
> +
> +       if (WARN_ON(gc->of_gpio_n_cells < 3))
> +               return -EINVAL;
> +
> +       if (WARN_ON(gpiospec->args_count < gc->of_gpio_n_cells))
> +               return -EINVAL;
> +
> +       if (gpiospec->args[0] > gc->ngpio)
> +               return -EINVAL;
> +
> +       pin = gc->base + gpiospec->args[0];
> +
> +       if (s3c_gpio_cfgpin(pin, S3C_GPIO_SFN(gpiospec->args[1])))
> +               pr_warn("gpio_xlate: failed to set pin function\n");
> +       if (s3c_gpio_setpull(pin, gpiospec->args[2] & 0xffff))
> +               pr_warn("gpio_xlate: failed to set pin pull up/down\n");
> +
> +       if (flags)
> +               *flags = gpiospec->args[2] >> 16;
> +
> +       return gpiospec->args[0];
> +}
> +
> +static const struct of_device_id s3c24xx_gpio_dt_match[] __initdata = {
> +       { .compatible = "samsung,s3c24xx-gpio", },
> +       {}
> +};
> +
> +static __init void s3c24xx_gpiolib_attach_ofnode(struct samsung_gpio_chip *chip,
> +                                                u64 base, u64 offset)
> +{
> +       struct gpio_chip *gc =  &chip->chip;
> +       u64 address;
> +
> +       if (!of_have_populated_dt())
> +               return;
> +
> +       address = chip->base ? base + ((u32)chip->base & 0xfff) : base + offset;
> +       gc->of_node = of_find_matching_node_by_address(NULL,
> +                       s3c24xx_gpio_dt_match, address);
> +       if (!gc->of_node) {
> +               pr_info("gpio: device tree node not found for gpio controller"
> +                       " with base address %08llx\n", address);
> +               return;
> +       }
> +       gc->of_gpio_n_cells = 3;
> +       gc->of_xlate = s3c24xx_gpio_xlate;
> +}
> +#elif defined(CONFIG_PLAT_S3C24XX)
> +static __init void s3c24xx_gpiolib_attach_ofnode(struct samsung_gpio_chip *chip,
> +                                                u64 base, u64 offset)
> +{
> +       return;
> +}
> +#endif /* defined(CONFIG_PLAT_S3C24XX) && defined(CONFIG_OF) */
> +
>  static void __init s3c24xx_gpiolib_add_chips(struct samsung_gpio_chip *chip,
>                                              int nr_chips, void __iomem *base)
>  {
> @@ -962,6 +1023,8 @@ static void __init s3c24xx_gpiolib_add_chips(struct samsung_gpio_chip *chip,
>                         gc->direction_output = samsung_gpiolib_2bit_output;
>
>                 samsung_gpiolib_add(chip);
> +
> +               s3c24xx_gpiolib_attach_ofnode(chip, S3C24XX_PA_GPIO, i * 0x10);
>         }
>  }
>
> --
> 1.7.2.3
>

Overall, this is patch looks fine.

Reviewed-by: Thomas Abraham <thomas.abraham at linaro.org>