linux-kernel - Re: [PATCH 0/3] phy: qcom: edp: Add support for DT phy mode configuration

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Date: Thu, 21 Dec 2023 18:27:58 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abel Vesa <abel.vesa@...aro.org>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Johan Hovold <johan@...nel.org>, linux-phy@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH 0/3] phy: qcom: edp: Add support for DT phy mode configuration

On Tue, 19 Dec 2023 at 22:55, Abel Vesa <abel.vesa@...aro.org> wrote:
>
> Until now, all platform that supported both eDP and DP had different
> compatibles for each mode. Using different compatibles for basically
> the same IP block but for a different configuration is bad way all
> around. There is a new compute platform from Qualcomm that supports
> both eDP and DP with the same PHY. So instead of following the old
> method, we should allow the mode to be configured from devicetree.
>
> There has been an off-list discussion on what would be the right way
> to pass on the PHY mode information to the driver and it has been
> concluded that phy-cells is the way to go. This means that basically
> the controller will pass another value (that is, the PHY type) to
> its 'phys' DT property.
>
> For this, we need both the bindings value and the PHY mode value to be
> added as well.
>
> The controller part will follow shortly. But for now, lets see where
> this is going.
>
> There has been another attempt at this here:
> https://lore.kernel.org/all/20231122-phy-qualcomm-edp-x1e80100-v3-3-576fc4e9559d@linaro.org/
>
> Compared to that version, this one uses the phy-cells method and drops
> the X1E80100 support. The X1E80100 support will be a separate patchset.

After several back and forth discussions, I think that this approach
is not correct and not that easy to extend. Instead I'd like to
suggest adding a property to the DP controller, which enables eDP
behaviour (and thus makes DP driver call phy_set_mode()). Something
like this:
dp: displayport-controller@...000 {
    compatible = "qcom,sm8000-dp";
    /* reg, interrupts, etc */
   edp-interface;
   /* or simpler */
   is-edp;
};

What do you think?

-- 
With best wishes
Dmitry