linux-kernel - Re: [PATCH] arm64: dts: qcom: sc8280xp-x13s: Use the correct DP PHY compatible

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Message-ID: <ZSz7---IW_7Oj2Zr@hovoldconsulting.com>
Date:   Mon, 16 Oct 2023 11:01:47 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sc8280xp-x13s: Use the correct DP PHY
 compatible

On Mon, Oct 16, 2023 at 11:51:33AM +0300, Dmitry Baryshkov wrote:
> On Fri, 29 Sept 2023 at 19:03, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
> >
> > The DP PHY needs different settings when an eDP display is used.
> > Make sure these apply on the X13s.
> 
> Could you please clarify, is it the same PHY type, just being
> repurposed for eDP or is it a different PHY type?

Same PHY, just different settings AFAIK.

> If the former is the case (and the same PHY can be used for both DP
> and eDP), it should carry the same compatible string and use software
> mechanisms (e.g. phy_set_mode_ext()) to be programmed for the correct
> operation mode.

Possibly, but that's not how the current binding and implementation
works:

	6993c079cd58 ("dt-bindings: phy: qcom-edp: Add SC8280XP PHY compatibles")
	2300d1cb24b3 ("phy: qcom: edp: Introduce support for DisplayPort")
	3b7267dec445 ("phy: qcom: edp: Add SC8280XP eDP and DP PHYs")

	https://lore.kernel.org/lkml/20220810040745.3582985-1-bjorn.andersson@linaro.org/

And you'd still need to infer the mode from DT somehow.

Johan