linux-kernel - [PATCH] leds: pwm: Disable PWM when going to suspend

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Date: Wed, 17 Apr 2024 17:38:47 +0200
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Lee Jones <lee@...nel.org>
Cc: Linux regressions mailing list <regressions@...ts.linux.dev>,
	linux-leds@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	kernel@...gutronix.de
Subject: [PATCH] leds: pwm: Disable PWM when going to suspend

On stm32mp1xx based machines (and others) a PWM consumer has to disable
the PWM because an enabled PWM refuses to suspend. So check the
LED_SUSPENDED flag and depending on that set the .enabled property.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=218559
Fixes: 76fe464c8e64 ("leds: pwm: Don't disable the PWM when the LED should be off")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello,

On Wed, Apr 17, 2024 at 03:49:43PM +0100, Lee Jones wrote:
> On Tue, 16 Apr 2024, Uwe Kleine-König wrote:
> > If you don't consider that suitable, I can create a patch that is easier
> > to pick up.
> 
> Yes, please submit it properly.

Here it comes.

Best regards
Uwe

 drivers/leds/leds-pwm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
index 4e3936a39d0e..e1b414b40353 100644
--- a/drivers/leds/leds-pwm.c
+++ b/drivers/leds/leds-pwm.c
@@ -53,7 +53,13 @@ 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 = true;
+	/*
+	 * Disabling a PWM doesn't guarantee that it emits the inactive level.
+	 * So keep it on. Only for suspending the PWM should be disabled because
+	 * otherwise it refuses to suspend. The possible downside is that the
+	 * LED might stay (or even go) on.
+	 */
+	led_dat->pwmstate.enabled = !(led_cdev->flags & LED_SUSPENDED);
 	return pwm_apply_might_sleep(led_dat->pwm, &led_dat->pwmstate);
 }
 

base-commit: 4eab358930711bbeb85bf5ee267d0d42d3394c2c
-- 
2.43.0