linux-kernel - Re: [PATCH RFC] arm64: dts: mediatek: mt8195-cherry: Remove keyboard-backlight node

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Message-ID: <CAGXv+5F=sRPi7sQrxyzM7t5gbZYzOE1oymxeJEvmkCtPT6QHTQ@mail.gmail.com>
Date: Tue, 16 Jul 2024 16:56:30 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thomas Weißschuh <linux@...ssschuh.net>, 
	Tzung-Bi Shih <tzungbi@...nel.org>, kernel@...labora.com, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH RFC] arm64: dts: mediatek: mt8195-cherry: Remove
 keyboard-backlight node

On Tue, Jul 16, 2024 at 12:13 AM Nícolas F. R. A. Prado
<nfraprado@...labora.com> wrote:
>
> Commit 970c3a6b7aa3 ("mfd: cros_ec: Register keyboard backlight
> subdevice") introduced support for detecting keyboard backlight
> fuctionality through communication with the ChromeOS EC. This means that
> the DT node is no longer used. Remove the unneeded node.
>
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> ---
> Different CrosEC FW versions could potentially not support discovering
> the keyboard backlight functionality, but I've tested both a recent
>
>   tomato_v2.0.23149-099cd3e539 tomato_15699.72.0 2024-01-03
>
> and an old
>
>   tomato_v2.0.10686-234e646fd8 tomato_14268.0.0 2021-10-07
>
> version on mt8195-cherry-tomato and on both relying only on the
> discoverability works. I've tested on both tomato-r2 and tomato-r3. I
> have not tested on dojo, however, as I don't have access to it.

I grabbed one from our warehouse and this works as explained. So,

Tested-by: Chen-Yu Tsai <wenst@...omium.org>

Note that there's actually one SKU family for Dojo that doesn't have
the keyboard backlight, which I haven't tested yet. It also needs
a new device tree to describe the slightly different keyboard layout.

> My motivation to remove the node is because the DT kselftest expects DT
> nodes that can match to a driver to be probed, and with the "breaking"
> commit, the DT node goes unprobed which results in a failure:
>
>   not ok 225 /soc/spi@...0a000/ec@...eyboard-backlight
>
> I can also solve this in a different way, by adding this driver to the
> ignore list of the test. But this solution seemed better as the DT
> isn't meant to describe devices that can be discovered at run time
> anyway.

I think this makes sense.

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

> ---
>  arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi | 4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> index fe5400e17b0f..20dfa18c9dda 100644
> --- a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> +++ b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
> @@ -1228,10 +1228,6 @@ cros_ec: ec@0 {
>                 spi-max-frequency = <3000000>;
>                 wakeup-source;
>
> -               keyboard-backlight {
> -                       compatible = "google,cros-kbd-led-backlight";
> -               };
> -
>                 i2c_tunnel: i2c-tunnel {
>                         compatible = "google,cros-ec-i2c-tunnel";
>                         google,remote-bus = <0>;
>
> ---
> base-commit: 91e3b24eb7d297d9d99030800ed96944b8652eaf
> change-id: 20240715-cros-backlight-dt-probe-7754a832ad60
>
> Best regards,
> --
> Nícolas F. R. A. Prado <nfraprado@...labora.com>
>
>