linux-kernel - Re: [PATCH 3/7] arm64: dts: qcom: sc7280: Hook up the touchscreen IO rail on villager

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Message-ID: <Y+KV4D0iAp1GxY2p@google.com>
Date:   Tue, 7 Feb 2023 18:18:08 +0000
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        devicetree@...r.kernel.org, Stephen Kitt <steve@....org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Gross <agross@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] arm64: dts: qcom: sc7280: Hook up the touchscreen IO
 rail on villager

On Mon, Feb 06, 2023 at 06:48:12PM -0800, Douglas Anderson wrote:
> On never revs of sc7280-herobrine-villager (rev2+) the L3C rail is

nit: s/never/newer/

no need to re-spin just for this.

> provided to the touchscreen as the IO voltage rail. Let's add it in
> the device tree.
> 
> NOTE: Even though this is only really needed on rev2+ villagers (-rev0
> had non-functioning touchscreen and -rev1 had some hacky hardware
> magic), it doesn't actually hurt to do this for old villager revs. As
> talked about in the patch ("arm64: dts: qcom: sc7280: On QCard,
> regulator L3C should be 1.8V") the L3C regulator didn't go anywhere at
> all on older revs. That means that turning it on for older revs
> doesn't hurt other than drawing a tiny bit of extra power. Since -rev0
> and -rev1 villagers will never make it to real customers and it's nice
> not to have too many old device trees, the better tradeoff seems to be
> to enable it everywhere.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Matthias Kaehlcke <mka@...omium.org>