4.19-stable review patch. If anyone has any objections, please let me know.
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From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
[ Upstream commit 76fe464c8e64e71b2e4af11edeef0e5d85eeb6aa ]
Disabling a PWM (i.e. calling pwm_apply_state with .enabled = false) gives no guarantees what the PWM output does. It might freeze where it currently is, or go in a High-Z state or drive the active or inactive state, it might even continue to toggle.
To ensure that the LED gets really disabled, don't disable the PWM even when .duty_cycle is zero.
This fixes disabling a leds-pwm LED on i.MX28. The PWM on this SoC is one of those that freezes its output on disable, so if you disable an LED that is full on, it stays on. If you disable a LED with half brightness it goes off in 50% of the cases and full on in the other 50%.
Fixes: 41c42ff5dbe2 ("leds: simple driver for pwm driven LEDs") Reported-by: Rogan Dawes rogan@dawes.za.net Reported-by: Fabio Estevam festevam@denx.de Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Reviewed-by: Fabio Estevam festevam@denx.de Link: https://lore.kernel.org/r/20230922192834.1695727-1-u.kleine-koenig@pengutron... Signed-off-by: Lee Jones lee@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/leds/leds-pwm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c index 16c78df7a7632..107e635cac245 100644 --- a/drivers/leds/leds-pwm.c +++ b/drivers/leds/leds-pwm.c @@ -49,7 +49,7 @@ static int led_pwm_set(struct led_classdev *led_cdev, duty = led_dat->pwmstate.period - duty;
led_dat->pwmstate.duty_cycle = duty; - led_dat->pwmstate.enabled = duty > 0; + led_dat->pwmstate.enabled = true; return pwm_apply_state(led_dat->pwm, &led_dat->pwmstate); }