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

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Message-Id: <D913G6I023M1.NLMLJDZ1PYSA@bootlin.com>
Date: Tue, 08 Apr 2025 09:54:27 +0200
From: "Thomas Bonnefille" <thomas.bonnefille@...tlin.com>
To: "Inochi Amaoto" <inochiama@...il.com>, 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

On Mon Apr 7, 2025 at 9:21 AM CEST, Inochi Amaoto wrote:
> On Sun, Apr 06, 2025 at 02:16:41AM +0200, Thomas Bonnefille wrote:
>> 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
>
> I suggest checking existing spi-sg2044-nor driver, which may reduce your
> work for upstreaming.
>
> Regards,
> Inochi

Hello Inochi,

Thank you very much, however even after reading it I can't see the link
between the SPI NOR controller driver of the SG2044 and the PWM driver
for the CV18XX series ?

Regards,
Thomas