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

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Message-ID: <CA+ASDXOtyBgr0o+bhjOScjs2h3oUKdouoAi4m+Z=R=Bho=iRFA@mail.gmail.com>
Date:   Thu, 30 Mar 2023 15:20:16 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
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

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
> 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
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>