linux-kernel - Re: [PATCH] arm64: dts: rockchip: Remove non-existing pwm-delay-us DT property

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Message-ID: <87355lg81f.fsf@minerva.mail-host-address-is-not-set>
Date:   Fri, 31 Mar 2023 00:59:24 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Enric Balletbo i Serra <eballetbo@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Judy Hsiao <judyhsiao@...omium.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lin Huang <hl@...k-chips.com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, zain wang <wzz@...k-chips.com>
Subject: Re: [PATCH] arm64: dts: rockchip: Remove non-existing pwm-delay-us
 DT property

Brian Norris <briannorris@...omium.org> writes:

Hello Brian,

> On Thu, Mar 30, 2023 at 3:03 PM Javier Martinez Canillas
> <javierm@...hat.com> wrote:
>>
>> There is no neither a driver that parses this nor a DT binding schema that

Ups, I noticed now that there's an unnecessary "no" and it should be instead:

"There is neither a driver..."

>> documents it so let's remove it from the DTS files that make use of this.
>>
>> The properties that exist are post-pwm-on-delay-ms and pwm-off-delay-ms,
>> defined in the pwm-backlight DT binding. So probably what these DTS want
>> is something like following:
>>
>>         backlight: backlight {
>>                 compatible = "pwm-backlight";
>>                 enable-gpios = <&gpio4 21 GPIO_ACTIVE_HIGH>;
>>                 pinctrl-names = "default";
>>                 pinctrl-0 = <&bl_en>;
>>                 pwms = <&pwm1 0 1000000 0>;
>>                 post-pwm-on-delay-ms = <10>;
>>                 pwm-off-delay-ms = <10>;
>>         };
>>
>> But that should be follow-up change if that is the case. Because otherwise
>> it would be change in behaviour, since currently pwm-delay-us is a no-op.
>>
>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>
> pwm-delay-us seems to have been a downstream-only ("CHROMIUM", if
> you're familiar with ChromiumOS kernel parlance) change that seems
> like a combination of the two now-upstream properties you point at. I

Yes, that's what I found too. So it seems that this was an oversight when
the DTS for these Chromebooks were upstreamed.

> looked through the first use of pwm-delay-us on RK3399 Gru systems,
> and I can't find a spec reference that said it was needed; perhaps it
> was needless copy/paste imitation?
>
> So, simple deletion is probably fine:
>
> Reviewed-by: Brian Norris <briannorris@...omium.org>
>

Thanks for the confirmation and review!

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat