pwm: stm32: Always do lazy disabling

[ Upstream commit 7346e7a058a2c9aa9ff1cc699c7bf18a402d9f84 ]

When the state changes from enabled to disabled, polarity, duty_cycle
and period are not configured in hardware and TIM_CCER_CCxE is just
cleared. However if the state changes from one disabled state to
another, all parameters are written to hardware because the early exit
from stm32_pwm_apply() is only taken if the pwm is currently enabled.

This yields surprises like: Applying

	{ .period = 1, .duty_cycle = 0, .enabled = false }

succeeds if the pwm is initially on, but fails if it's already off
because 1 is a too small period.

Update the check for lazy disable to always exit early if the target
state is disabled, no matter what is currently configured.

Fixes: 7edf736920 ("pwm: Add driver for STM32 plaftorm")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/20240703110010.672654-2-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/pwm/pwm-stm32.c

@@ -452,8 +452,9 @@ static int stm32_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	enabled = pwm->state.enabled;
 
-	if (enabled && !state->enabled) {
-		stm32_pwm_disable(priv, pwm->hwpwm);
+	if (!state->enabled) {
+		if (enabled)
+			stm32_pwm_disable(priv, pwm->hwpwm);
 		return 0;
 	}