pwm: pxa: Set duty cycle to 0 when disabling PWM

When disabling PWM, the duty cycle needs to be set to 0. This prevents
the previous duty cycle from showing up momentarily when the clock is
re-enabled next time.

Because the clock has to be running in order to configure the duty
cycle, unconditionally enable it early in pxa_pwm_apply and account for
the correct enable count at the end.
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Doug Brown <doug@schmorgal.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20221113233639.24244-3-doug@schmorgal.comSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/pwm-pxa.c

@@ -105,24 +105,31 @@ static int pxa_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			 const struct pwm_state *state)
 {
 	struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
+	u64 duty_cycle;
 	int err;
 
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
 
-	if (!state->enabled) {
-		if (pwm->state.enabled)
-			clk_disable_unprepare(pc->clk);
+	err = clk_prepare_enable(pc->clk);
+	if (err)
+		return err;
 
-		return 0;
-	}
+	duty_cycle = state->enabled ? state->duty_cycle : 0;
 
-	err = pxa_pwm_config(chip, pwm, state->duty_cycle, state->period);
-	if (err)
+	err = pxa_pwm_config(chip, pwm, duty_cycle, state->period);
+	if (err) {
+		clk_disable_unprepare(pc->clk);
 		return err;
+	}
+
+	if (state->enabled && !pwm->state.enabled)
+		return 0;
+
+	clk_disable_unprepare(pc->clk);
 
-	if (!pwm->state.enabled)
-		return clk_prepare_enable(pc->clk);
+	if (!state->enabled && pwm->state.enabled)
+		clk_disable_unprepare(pc->clk);
 
 	return 0;
 }