Commit b2eaa117 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Uwe Kleine-König
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pwm: Assume a disabled PWM to emit a constant inactive output 



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: default avatarDimitri Fedrau <dima.fedrau@gmail.com>
Link: https://lore.kernel.org/r/20241103205215.GA509903@debian


Fixes: 3ad1f3a3 ("pwm: Implement some checks for lowlevel drivers")
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: default avatarDimitri Fedrau <dima.fedrau@gmail.com>
Tested-by: default avatarDimitri Fedrau <dima.fedrau@gmail.com>
Link: https://lore.kernel.org/r/20241105153521.1001864-2-u.kleine-koenig@baylibre.com


Signed-off-by: default avatarUwe Kleine-König <ukleinek@kernel.org>
parent 2ea25aab

drivers/pwm/core.c

+7 −3
Original line number Diff line number Diff line
@@ -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,