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

[Tom Rini]

On Wed, Apr 06, 2022 at 08:30:31AM -0700, Tim Harvey wrote:
> On Wed, Apr 6, 2022 at 5:27 AM Tom Rini <trini at konsulko.com> wrote:
> >
> > 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,
> 
> That's kind of funny I suppose because the behavior is clearly wrong.
> 
> Is fixing the test something that needs to be done for the patch to be
> applied, or needs to be done by me? I'm not familiar with the test
> framework or how to execute it.

For running the tests, please see:
https://u-boot.readthedocs.io/en/latest/develop/testing.html
and you're going to need to take a look at test/dm/gpio.c as where to
fix what.  And yes, a v2 that addresses the test as well is what I need.
Thanks!

-- 
Tom
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