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 <[email protected]>
> Signed-off-by: Tim Harvey <[email protected]>This breaks the ut_dm_dm_test_gpio test which I guess needs to be updated. -- Tom
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