linux-kernel - Re: [PATCH v7 2/2] pwm: sophgo: add pwm support for Sophgo CV1800 SoC

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Message-Id: <D8Z4GLQZGKKS.37TDZ7QBN4V4N@bootlin.com>
Date: Sun, 06 Apr 2025 02:16:41 +0200
From: "Thomas Bonnefille" <thomas.bonnefille@...tlin.com>
To: Uwe Kleine-König <ukleinek@...nel.org>, "Jingbao Qiu"
 <qiujingbao.dlmu@...il.com>
Cc: <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
 <unicorn_wang@...look.com>, <dlan@...too.org>, <linux-pwm@...r.kernel.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/2] pwm: sophgo: add pwm support for Sophgo CV1800
 SoC

Hello,

On Sat Jun 1, 2024 at 1:53 PM CEST, Uwe Kleine-König wrote:
> On Wed, May 01, 2024 at 04:32:42PM +0800, Jingbao Qiu wrote:
>> [...]
>> +	if ((state & BIT(pwm->hwpwm)) && enable)
>> +		regmap_update_bits(priv->map, PWM_CV1800_OE,
>> +				   PWM_CV1800_OE_MASK(pwm->hwpwm),
>> +				   PWM_CV1800_REG_ENABLE(pwm->hwpwm));
>
> This looks strange. If BIT(hwpwm) is already set, set it again?!
> Also if you used the caching implemented in regmap, you don't need to
> make this conditional.
>

I was testing the series and noticed indeed an issue in this driver at
those lines. If PWM_CV1800_OE isn't set by something else than the
kernel it will never be set and so, there will never be a PWM outputted.

Using :
    if (!(state & BIT(pwm->hwpwm)) && enable)
Solved the issue but as Uwe said you can probably rely on regmap caching
to avoid this condition.

>
> ...
> 

Do you plan on sending a new iteration some day ? I may have some time
to continue the upstreaming process if you need to.

Thank you for this series !
Thomas