linux-kernel - Re: [regression] stm32mp1xx based targets stopped entering suspend if pwm-leds exist

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Message-ID: <20240416121519.GS2399047@google.com>
Date: Tue, 16 Apr 2024 13:15:19 +0100
From: Lee Jones <lee@...nel.org>
To: Linux regressions mailing list <regressions@...ts.linux.dev>
Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	linux-leds@...r.kernel.org, linux-pwm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [regression] stm32mp1xx based targets stopped entering suspend
 if pwm-leds exist

On Tue, 16 Apr 2024, Linux regression tracking (Thorsten Leemhuis) wrote:

> On 06.03.24 09:18, Uwe Kleine-König wrote:
> > On Wed, Mar 06, 2024 at 08:05:15AM +0100, Linux regression tracking (Thorsten Leemhuis) wrote:
> >>
> >> Uwe, I noticed a report about a regression in bugzilla.kernel.org that
> >> apparently is caused by a change of yours. As many (most?) kernel
> >> developers don't keep an eye on it, I decided to forward it by mail.
> >>
> >> Note, you have to use bugzilla to reach the reporter, as I sadly[1] can
> >> not CCed them in mails like this.
> >>
> >> Quoting from https://bugzilla.kernel.org/show_bug.cgi?id=218559 :
> >>
> >>> Commit 76fe464c8e64e71b2e4af11edeef0e5d85eeb6aa ("leds: pwm: Don't
> >>> disable the PWM when the LED should be off") prevents stm32mp1xx based
> >>> targets from entering suspend if pwm-leds exist, as the stm32 PWM driver
> >>> refuses to enter suspend if any PWM channels are still active ("PWM 0
> >>> still in use by consumer" see stm32_pwm_suspend in drivers/pwm/stm32-pwm.c).
> >>>
> >>> Reverting the mentioned commit fixes this behaviour but I'm not
> >>> certain if this is a problem with stm32-pwm or pwm-leds (what is the
> >>> usual behaviour for suspend with active PWM channels?).
> > 
> > I'd assume the following patch fixes this report. I didn't test it
> > though.
> 
> Jakob confirmed it helped in the bugzilla ticket. But the patch since
> then didn't make any progress afaics -- or did it and I just missed it
> in my search?

[...] 

> > ---->8----
> > From: Uwe Kleine-König <u.kleine-koenig@...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>
> > ---
> >  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: 15facbd7bd3dbfa04721cb71e69954eb4686cb9e
> > ---->8----

Did you submit this?  I don't see it in LORE or in my inbox.

-- 
Lee Jones [李琼斯]