Hi Simon,
2015-07-03 9:15 GMT+09:00 Simon Glass <s...@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 <s...@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
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