This is a note to let you know that I've just added the patch titled
pwm: Assume a disabled PWM to emit a constant inactive output
to the 6.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pwm-assume-a-disabled-pwm-to-emit-a-constant-inactiv.patch
and it can be found in the queue-6.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8e9fec593440a1927d42bd4a8d56da79f8fb54bd
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
Date: Tue Nov 5 16:35:22 2024 +0100
pwm: Assume a disabled PWM to emit a constant inactive output
[ Upstream commit b2eaa1170e45dc18eb09dcc9abafbe9a7502e960 ]
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@xxxxxxxxx>
Link: https://lore.kernel.org/r/20241103205215.GA509903@debian
Fixes: 3ad1f3a33286 ("pwm: Implement some checks for lowlevel drivers")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
Reviewed-by: Dimitri Fedrau <dima.fedrau@xxxxxxxxx>
Tested-by: Dimitri Fedrau <dima.fedrau@xxxxxxxxx>
Link: https://lore.kernel.org/r/20241105153521.1001864-2-u.kleine-koenig@xxxxxxxxxxxx
Signed-off-by: Uwe Kleine-König <ukleinek@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 8acbcf5b66739..53c3a76a185ed 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -75,7 +75,7 @@ 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)
@@ -83,7 +83,11 @@ 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);
@@ -99,7 +103,7 @@ 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,
