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| author | Uwe Kleine-König <u.kleine-koenig@baylibre.com> | 2024-11-05 16:35:22 +0100 |
|---|---|---|
| committer | Uwe Kleine-König <ukleinek@kernel.org> | 2024-11-07 12:03:39 +0100 |
| commit | b2eaa1170e45dc18eb09dcc9abafbe9a7502e960 (patch) | |
| tree | e228ed35fefeb29c9aa90f71e4bb20db2d1e2da1 | |
| parent | 2ea25aab938a250bdf3148acd15359b56b91b40e (diff) | |
| download | lwn-b2eaa1170e45dc18eb09dcc9abafbe9a7502e960.tar.gz lwn-b2eaa1170e45dc18eb09dcc9abafbe9a7502e960.zip | |
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: Dimitri Fedrau <dima.fedrau@gmail.com>
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@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>
| -rw-r--r-- | drivers/pwm/core.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index ccbdd6dd1410..9c733877e98e 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -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, |