linux-kernel - Re: [PATCH v2] pwm: stm32: Always program polarity

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Message-ID: <j7qywnmejd4v2tez77hxmjnq7pavmaoed7z4aoelsbfdyt4qyx@7jawgsz2kfy7>
Date: Thu, 8 Jan 2026 17:01:41 +0100
From: Uwe Kleine-König <ukleinek@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Sasha Levin <sashal@...nel.org>
Cc: Sean Nyekjaer <sean@...nix.com>, 
	Fabrice Gasnier <fabrice.gasnier@...s.st.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, linux-pwm@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] pwm: stm32: Always program polarity

Hello Greg,

On Thu, Jan 08, 2026 at 01:45:23PM +0100, Sean Nyekjaer wrote:
> Commit 7346e7a058a2 ("pwm: stm32: Always do lazy disabling") triggered a
> regression where PWM polarity changes could be ignored.
> 
> stm32_pwm_set_polarity() was skipped due to a mismatch between the
> cached pwm->state.polarity and the actual hardware state, leaving the
> hardware polarity unchanged.
> 
> Fixes: 7edf7369205b ("pwm: Add driver for STM32 plaftorm")
> Cc: stable@...r.kernel.org # <= 6.12
> Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> Co-developed-by: Uwe Kleine-König <ukleinek@...nel.org>
Signed-off-by: Uwe Kleine-König <ukleinek@...nel.org>

> ---
> This patch is only applicable for stable tree's <= 6.12

Can you please apply this patch to v6.12.x and older? The problem fixed
here doesn't happen in mainline since commit deaba9cff809 ("pwm: stm32:
Implementation of the waveform callbacks"). That mainline commit however
is too intrusive to backport it to stable, not even considering its
dependencies (e.g. 17e40c25158f ("pwm: New abstraction for PWM
waveforms")). 

I assume such an exception to the sable process is ok and the patch is
simple enough to be easily reviewable? If not, tell me, then I can apply
the patch and merge it (with `-s ours`) into my next PWM pull request to
Linus :-)

Best regards
Uwe

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