[U-Boot] [PATCH 19/55] dm: gpio: Add support for setting a GPIO's pull direction

[Masahiro Yamada <yamada.masahiro@socionext.com>]

Hi Simon,


2015-07-03 9:15 GMT+09:00 Simon Glass <sjg@chromium.org>:
> At present the driver model GPIO API does not support pull-up/pull-down on
> input GPIOs. This is required in some cases.
>
> Add this feature to the API with two new methods that drivers can optionally
> implement.
>
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
>
>  drivers/gpio/gpio-uclass.c | 31 +++++++++++++++++++++++++++++++
>  include/asm-generic/gpio.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 77 insertions(+)
>
> diff --git a/drivers/gpio/gpio-uclass.c b/drivers/gpio/gpio-uclass.c
> index 4efda31..c4ba580 100644
> --- a/drivers/gpio/gpio-uclass.c
> +++ b/drivers/gpio/gpio-uclass.c
> @@ -374,6 +374,37 @@ int dm_gpio_set_dir(struct gpio_desc *desc)
>         return dm_gpio_set_dir_flags(desc, desc->flags);
>  }
>
> +int dm_gpio_set_pull(struct gpio_desc *desc, enum gpio_pull pull)
> +{
> +       struct dm_gpio_ops *ops = gpio_get_ops(desc->dev);
> +       int ret;
> +
> +       ret = check_reserved(desc, "set_pull");
> +       if (ret)
> +               return ret;
> +
> +       if (!ops->set_pull)
> +               return -ENOSYS;
> +
> +       return ops->set_pull(desc->dev, desc->offset, pull);
> +}
> +
> +int dm_gpio_get_pull(struct gpio_desc *desc, unsigned offset)
> +{
> +       struct dm_gpio_ops *ops = gpio_get_ops(desc->dev);
> +       int ret;
> +
> +       ret = check_reserved(desc, "get_pull");
> +       if (ret)
> +               return ret;
> +
> +       if (!ops->get_pull)
> +               return -ENOSYS;
> +
> +       return ops->get_pull(desc->dev, desc->offset);
> +}
> +
> +
>  /**
>   * gpio_get_value() - [COMPAT] Sample GPIO pin and return it's value
>   * gpio:       GPIO number
> diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
> index 0af599f..db5504f 100644
> --- a/include/asm-generic/gpio.h
> +++ b/include/asm-generic/gpio.h
> @@ -126,6 +126,13 @@ struct gpio_desc {
>          */
>  };
>
> +/* GPIO pull directions (used for input lines) */
> +enum gpio_pull {
> +       GPIO_PULL_NONE,
> +       GPIO_PULL_DOWN,
> +       GPIO_PULL_UP,
> +};
> +
>  /**
>   * dm_gpio_is_valid() - Check if a GPIO is valid
>   *
> @@ -276,6 +283,26 @@ struct dm_gpio_ops {
>          */
>         int (*xlate)(struct udevice *dev, struct gpio_desc *desc,
>                      struct fdtdec_phandle_args *args);
> +
> +       /**
> +        * set_pull() - set pull direction
> +        *
> +        * @dev:        Device to adjust
> +        * @offset:     GPIO offset within device
> +        * @pull:       New pull direction
> +        * @return 0 if OK, -ve on error
> +        */
> +       int (*set_pull)(struct udevice *dev, unsigned offset,
> +                       enum gpio_pull pull);
> +
> +       /**
> +        * get_pull() - get pull direction
> +        *
> +        * @dev:        Device to check
> +        * @offset:     GPIO offset within device
> +        * @return current pull direction or -ve on error
> +        */
> +       int (*get_pull)(struct udevice *dev, unsigned offset);
>  };
>


Do you want to control pull-up/down only for GPIOs?
Pin-biasing makes sense for dedicated functions as well as GPIOs.
At least, I am inclined to enable pull-up registers for SCL/SDA (I2C)
pins on my boards.

As far as I know, in Linux, such stuff is handled in pinctrl drivers.
I see no .set_pull() callback in struct gpio_chip in Linux.

As far as I see your pinctrl implementation,
(http://patchwork.ozlabs.org/patch/487801/)
it looks like "pinctrl = pinmuxing" in U-Boot, whereas "pinctrl =
pinmuxing + pin-configuration" in Linux.




-- 
Best Regards
Masahiro Yamada