linux-kernel - Re: [PATCH v9 0/3] Add support for Allwinner PWM on D1/T113s/R329 SoCs

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Message-ID: <CAG40kxG0yM0+ge3=zX4S_MQevuNQ5oWAvtmTPXAbHHk2nmSYew@mail.gmail.com>
Date: Fri, 24 May 2024 20:32:29 +0900
From: きくちゃんさん <kikuchan98@...il.com>
To: John Watts <contact@...kia.org>
Cc: privatesub2@...il.com, aou@...s.berkeley.edu, bigunclemax@...il.com, 
	conor+dt@...nel.org, devicetree@...r.kernel.org, fusibrandon13@...il.com, 
	jernej.skrabec@...il.com, krzk+dt@...nel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-pwm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, mkl@...gutronix.de, p.zabel@...gutronix.de, 
	palmer@...belt.com, paul.walmsley@...ive.com, robh@...nel.org, 
	samuel@...lland.org, ukleinek@...nel.org, wens@...e.org
Subject: Re: [PATCH v9 0/3] Add support for Allwinner PWM on D1/T113s/R329 SoCs

Hi John,

> Does Linux guarantee a flicker-free experience with setting up PWM
> channels, or that it doesn't affect other channels?
> How do other drivers handle this situation?

I've noticed that drivers/pwm/pwm-fsl-ftm.c and
drivers/pwm/pwm-microchip-core.c use a similar approach for shared
resources between PWM channels.
They simply fail if the settings are not applicable to the hardware,
much like this driver does. However, I have yet to find a driver that
aggressively changes another channel that is already running.

Maybe you're right; Linux might not guarantee anything about this.
I think all we can do is deliver the best experience to users within
such limitations.

Best regards,
kikuchan.