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pwm: Assume a disabled PWM to emit a constant inactive output

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Some PWM hardwares (e.g. MC33XS2410) cannot implement a zero duty cycle
but can instead disable the hardware which also results in a constant
inactive output.

There are some checks (enabled with CONFIG_PWM_DEBUG) to help
implementing a driver without violating the normal rounding rules. Make
them less strict to let above described hardware pass without warning.

Reported-by: Dimitri Fedrau <dima.fedrau@gmail.com>
Link: https://lore.kernel.org/r/20241103205215.GA509903@debian
Fixes: 3ad1f3a332 ("pwm: Implement some checks for lowlevel drivers")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Dimitri Fedrau <dima.fedrau@gmail.com>
Tested-by: Dimitri Fedrau <dima.fedrau@gmail.com>
Link: https://lore.kernel.org/r/20241105153521.1001864-2-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This commit is contained in:
Uwe Kleine-König 2024-11-05 16:35:22 +01:00 committed by Uwe Kleine-König
parent 2ea25aab93
commit b2eaa1170e
1 changed files with 7 additions and 3 deletions
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10
drivers/pwm/core.c
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@ -466,7 +466,7 @@ static void pwm_apply_debug(struct pwm_device *pwm,
state->duty_cycle < state->period)
dev_warn(pwmchip_parent(chip), ".apply ignored .polarity\n");
if (state->enabled &&
if (state->enabled && s2.enabled &&
last->polarity == state->polarity &&
last->period > s2.period &&
last->period <= state->period)
@ -474,7 +474,11 @@ static void pwm_apply_debug(struct pwm_device *pwm,
".apply didn't pick the best available period (requested: %llu, applied: %llu, possible: %llu)\n",
state->period, s2.period, last->period);
if (state->enabled && state->period < s2.period)
/*
* Rounding period up is fine only if duty_cycle is 0 then, because a
* flat line doesn't have a characteristic period.
*/
if (state->enabled && s2.enabled && state->period < s2.period && s2.duty_cycle)
dev_warn(pwmchip_parent(chip),
".apply is supposed to round down period (requested: %llu, applied: %llu)\n",
state->period, s2.period);
@ -490,7 +494,7 @@ static void pwm_apply_debug(struct pwm_device *pwm,
s2.duty_cycle, s2.period,
last->duty_cycle, last->period);
if (state->enabled && state->duty_cycle < s2.duty_cycle)
if (state->enabled && s2.enabled && state->duty_cycle < s2.duty_cycle)
dev_warn(pwmchip_parent(chip),
".apply is supposed to round down duty_cycle (requested: %llu/%llu, applied: %llu/%llu)\n",
state->duty_cycle, state->period,