[PATCH] pwm: Prevent a glitch in compat code

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

When a PWM is to be disabled, configuring the duty cycle and
period before actually disabling the hardware might result in either a
glitch or a delay. So check for disabling first and return early in this
case.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/pwm/core.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 4058d3c86a45..4604ca3e0e62 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -597,6 +597,12 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
 			pwm->state.polarity = state->polarity;
 		}
 
+		if (!state->enabled && pwm->state.enabled) {
+			chip->ops->disable(chip, pwm);
+			pwm->state.enabled = false;
+			return 0;
+		}
+
 		if (state->period != pwm->state.period ||
 		    state->duty_cycle != pwm->state.duty_cycle) {
 			int duty_cycle, period;
@@ -620,16 +626,12 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
 			pwm->state.period = state->period;
 		}
 
-		if (state->enabled != pwm->state.enabled) {
-			if (state->enabled) {
-				err = chip->ops->enable(chip, pwm);
-				if (err)
-					return err;
-			} else {
-				chip->ops->disable(chip, pwm);
-			}
+		if (!pwm->state.enabled) {
+			err = chip->ops->enable(chip, pwm);
+			if (err)
+				return err;
 
-			pwm->state.enabled = state->enabled;
+			pwm->state.enabled = true;
 		}
 	}
 
-- 
2.30.1