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pwm: microchip-core: fix incorrect comparison with max period

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In mchp_core_pwm_apply_locked(), if hw_period_steps is equal to its max,
an error is reported and .apply fails. The max value is actually a
permitted value however, and so this check can fail where multiple
channels are enabled.

For example, the first channel to be configured requests a period that
sets hw_period_steps to the maximum value, and when a second channel
is enabled the driver reads hw_period_steps back from the hardware and
finds it to be the maximum possible value, triggering the warning on a
permitted value. The value to be avoided is 255 (PERIOD_STEPS_MAX + 1),
as that will produce undesired behaviour, so test for greater than,
rather than equal to.

Fixes: 2bf7ecf7b4ff ("pwm: add microchip soft ip corePWM driver")
Cc: stable@vger.kernel.org
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250122-pastor-fancied-0b993da2d2d2@spud
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This commit is contained in:
Conor Dooley 2025-01-22 14:42:56 +00:00 committed by Uwe Kleine-König
parent e8c59791eb
commit 752b6e3af3
1 changed files with 1 additions and 1 deletions
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2
drivers/pwm/pwm-microchip-core.c
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@ -327,7 +327,7 @@ static int mchp_core_pwm_apply_locked(struct pwm_chip *chip, struct pwm_device *
* mchp_core_pwm_calc_period().
* The period is locked and we cannot change this, so we abort.
*/
if (hw_period_steps == MCHPCOREPWM_PERIOD_STEPS_MAX)
if (hw_period_steps > MCHPCOREPWM_PERIOD_STEPS_MAX)
return -EINVAL;
prescale = hw_prescale;