[PATCH] driver: gpio: fix gpio glitch for output-high gpio-hog

[Tom Rini]

On Wed, Mar 02, 2022 at 06:01:08PM -0800, Tim Harvey wrote:

> A gpio-hog can be specified as output-low, output-high, or input where
> output-low means 'de-asserted' and 'output-high' means asserted vs
> voltage levels.
> 
> When a hog is probed gpio_request_tail() calls dm_gpio_set_dir_flags()
> which ends up setting the GPIO as an output with a driven 'de-asserted'
> value prior to setting the desired value the hog was configured for.
> While I'm not sure it makes sense to set the output level while simply
> 'requesting' a GPIO the result of this is that if the hog is configured
> for output-high the request call sets it first as output low before
> gpio_hog_probe() sets it to the configured value causing the gpio to
> 'glitch' which may be undesired for certain applications.
> 
> Fix this by setting the GPIOD_IS_OUT_ACTIVE flag for hogs configured as
> output-high.
> 
> This was tested with the following hogs:
> 
>         /* active-high output-low (de-asserted) GPIO should drive 0 */
>         gpio1 {
>                 gpio-hog;
>                 output-low;
>                 gpios = <1 GPIO_ACTIVE_HIGH>;
>                 line-name = "gpio1";
>         };
> 
>         /* active-high output-high (asserted) GPIO should drive 1 */
> 	/* before patch this would first drive 0 then 1 */
>         gpio2 {
>                 gpio-hog;
>                 output-high;
>                 gpios = <2 GPIO_ACTIVE_HIGH>;
>                 line-name = "gpio2";
>         };
> 
>         /* active-low output-low (de-asserted) GPIO should drive 1 */
>         gpio3 {
>                 gpio-hog;
>                 output-low;
>                 gpios = <3 GPIO_ACTIVE_LOW>;
>                 line-name = "gpio3#";
>         };
> 
>         /* active-low output-high (asserted) GPIO should drive 0 */
> 	/* before patch this would first drive 0 then 1 */
>         gpio4 {
>                 gpio-hog;
>                 output-high;
>                 gpios = <4 GPIO_ACTIVE_LOW>;
>                 line-name = "gpio4#";
>         };
> 
> Cc: Sean Anderson <sean.anderson at seco.com>
> Signed-off-by: Tim Harvey <tharvey at gateworks.com>

This breaks the ut_dm_dm_test_gpio test which I guess needs to be
updated.

-- 
Tom
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