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

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: [email protected]
Signed-off-by: Conor Dooley <[email protected]>
Link: https://lore.kernel.org/r/20250122-pastor-fancied-0b993da2d2d2@spud
Signed-off-by: Uwe Kleine-König <[email protected]>

diff --git a/drivers/pwm/pwm-microchip-core.c b/drivers/pwm/pwm-microchip-core.c
index c1f2287b8e9748f66bf4e96123725e2ffd576888..12821b4bbf97560638d848412851b195504aa3ad 100644 (file)
--- a/drivers/pwm/pwm-microchip-core.c
+++ b/drivers/pwm/pwm-microchip-core.c
@@ -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;