linux-kernel - Re: [PATCH 1/7] arm64: dts: qcom: sc7280: On QCard, regulator L3C should be 1.8V

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Message-ID: <Y+KUq8zc/kmtovVJ@google.com>
Date:   Tue, 7 Feb 2023 18:12:59 +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 1/7] arm64: dts: qcom: sc7280: On QCard, regulator L3C
 should be 1.8V

On Mon, Feb 06, 2023 at 06:48:10PM -0800, Douglas Anderson wrote:
> On the first sc7280 QCards the L3C rail was never really used for
> anything. Stuffing options on the QCard meant that the QCard itself
> didn't use this rail for anything. This rail did get sent to the
> mainboard, but no existing mainboards ever did anything with it other
> that route it to a testpoint.

nit: s/that/than/

no need to re-spin just for that

> On later sc7280 QCards, the L3C rail was repurposed. Instead of being
> a (nominally) 3.3V rail, it was decided to make it a 1.8V rail. It is
> now provided to the display connector (which might route it to the
> touchscreen) and also used to power some buffers relating to
> touchscreen IO. This rail is getting the additional tag "ts_avccio",
> though some places still refer to it as "vreg_l3c_3p0" despite the
> fact that the name now specifies the wrong voltage.
> 
> Since it never hurts for this rail to be 1.8V (even on old QCards /
> old boards), let's just change it to 1.8V across the board and add the
> extra "ts_avccio" moniker as a label in the device tree.
> 
> Future patches will start using this rail in their touchscreens.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

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