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pwm: meson: Explicitly set .polarity in .get_state()

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The driver only supports normal polarity. Complete the implementation of
.get_state() by setting .polarity accordingly.

This fixes a regression that was possible since commit c73a310762
("pwm: Handle .get_state() failures") which stopped to zero-initialize
the state passed to the .get_state() callback. This was reported at
https://forum.odroid.com/viewtopic.php?f=177&t=46360 . While this was an
unintended side effect, the real issue is the driver's callback not
setting the polarity.

There is a complicating fact, that the .apply() callback fakes support
for inversed polarity. This is not (and cannot) be matched by
.get_state(). As fixing this isn't easy, only point it out in a comment
to prevent authors of other drivers from copying that approach.

Fixes: c375bcbaab ("pwm: meson: Read the full hardware state in meson_pwm_get_state()")
Reported-by: Munehisa Kamata <kamatam@amazon.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20230310191405.2606296-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Uwe Kleine-König 2023-03-22 22:45:44 +01:00 • committed by Thierry Reding
parent 2be4dcf662
commit 8caa81eb95
1 changed files with 8 additions and 0 deletions
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8
drivers/pwm/pwm-meson.c
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@ -162,6 +162,12 @@ static int meson_pwm_calc(struct meson_pwm *meson, struct pwm_device *pwm,
duty = state->duty_cycle; duty = state->duty_cycle;
period = state->period; period = state->period;
/*
* Note this is wrong. The result is an output wave that isn't really
* inverted and so is wrongly identified by .get_state as normal.
* Fixing this needs some care however as some machines might rely on
* this.
*/
if (state->polarity == PWM_POLARITY_INVERSED) if (state->polarity == PWM_POLARITY_INVERSED)
duty = period - duty; duty = period - duty;
@ -358,6 +364,8 @@ static int meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
state->duty_cycle = 0; state->duty_cycle = 0;
} }
state->polarity = PWM_POLARITY_NORMAL;
return 0; return 0;
} }