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

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Date: Wed, 3 Jan 2024 14:42:49 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Abel Vesa <abel.vesa@...aro.org>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I
 <kishon@...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@...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 21.12.2023 17:27, Dmitry Baryshkov wrote:
> 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?

Please excuse my alzheimer, but why did we not go with phy-type after
the last discussion?

Konrad