linux-kernel - Re: [Freedreno] [PATCH v2 2/2] dt-bindings: display: msm/dsi: add qcom, dsi-phy-cphy-mode option

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Date:   Mon, 31 May 2021 21:10:19 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Jonathan Marek <jonathan@...ek.ca>, Rob Herring <robh@...nel.org>
Cc:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, David Airlie <airlied@...ux.ie>,
        freedreno@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <dri-devel@...ts.freedesktop.org>, Rob Clark <robdclark@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>, Sean Paul <sean@...rly.run>
Subject: Re: [Freedreno] [PATCH v2 2/2] dt-bindings: display: msm/dsi: add
 qcom, dsi-phy-cphy-mode option

On 28/05/2021 15:57, Jonathan Marek wrote:
> On 5/3/21 1:11 PM, Rob Herring wrote:
>> On Fri, Apr 23, 2021 at 01:24:40PM -0400, Jonathan Marek wrote:
>>> Document qcom,dsi-phy-cphy-mode option, which can be used to control
>>> whether DSI will operate in D-PHY (default) or C-PHY mode.
>>
>> Given this is a standard MIPI thing, I think this needs to be a common
>> property. We already have phy bindings that use the phy cells to set the
>> phy type which I think you should use here. See
>> include/dt-bindings/phy/phy.h.
>>
> 
> Is it OK to simply change the option to something like "phy-mode = 
> <PHY_TYPE_DSI_CPHY>;"?
> 
> (using phy-cells would be annoying to implement, with no benefit IMO)


To add another feather to the balance scales:

- `phys = <&dsi0_phy PHY_TYPE_DSI_CPHY>;` would bring knowledge about 
PHY mode to the DSI host (which does not really care about PHY mode)

- `phy-mode = <PHY_TYPE_DSI_CPHY>;` would stay in the PHY node, where 
this information belongs.

-- 
With best wishes
Dmitry