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Date: Wed, 3 Jan 2024 14:42:49 +0100
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Subject: Re: [PATCH 0/3] phy: qcom: edp: Add support for DT phy mode
 configuration
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To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
 Abel Vesa <abel.vesa@linaro.org>
Cc: Vinod Koul <vkoul@kernel.org>, Kishon Vijay Abraham I
 <kishon@kernel.org>, Bjorn Andersson <andersson@kernel.org>,
 Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Conor Dooley <conor+dt@kernel.org>, Johan Hovold <johan@kernel.org>,
 linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org,
 linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org
References: <20231219-x1e80100-phy-edp-compatible-refactor-v1-0-f9e77752953d@linaro.org>
 <CAA8EJpr8rKMBzcm-=HGu7-C5hPkNMrnG1cA78O00UjgJVT7p6Q@mail.gmail.com>
From: Konrad Dybcio <konrad.dybcio@linaro.org>
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On 21.12.2023 17:27, Dmitry Baryshkov wrote:
> On Tue, 19 Dec 2023 at 22:55, Abel Vesa <abel.vesa@linaro.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@ae0000 {
>     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