linux-kernel - Re: [PATCH v11 2/6] dt-bindings: display/msm: dp-controller: document QCS8300 compatible

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Message-ID: <pwbmqjspoyj2n7gchyaycxfp7ge46pyvm5dntkk7awkr6pblmi@wun2jdt5iehq>
Date: Mon, 8 Sep 2025 13:04:07 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Yongxing Mou <yongxing.mou@....qualcomm.com>
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 2/6] dt-bindings: display/msm: dp-controller:
 document QCS8300 compatible

On Mon, Sep 08, 2025 at 05:46:30PM +0800, Yongxing Mou wrote:
> 
> 
> On 9/5/2025 9:48 PM, Dmitry Baryshkov wrote:
> > On Fri, Sep 05, 2025 at 10:50:33AM +0800, Yongxing Mou wrote:
> > > 
> > > 
> > > On 9/4/2025 9:43 PM, Dmitry Baryshkov wrote:
> > > > On Thu, Sep 04, 2025 at 03:22:37PM +0800, Yongxing Mou wrote:
> > > > > Add compatible string for the DisplayPort controller found on the
> > > > > Qualcomm QCS8300 SoC.
> > > > > 
> > > > > The Qualcomm QCS8300 platform comes with one DisplayPort controller
> > > > > that supports 4 MST streams.
> > > > > 
> > > > > Signed-off-by: Yongxing Mou <yongxing.mou@....qualcomm.com>
> > > > > ---
> > > > >    .../bindings/display/msm/dp-controller.yaml        | 22 ++++++++++++++++++++++
> > > > >    1 file changed, 22 insertions(+)
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > > > > index aeb4e4f36044a0ff1e78ad47b867e232b21df509..ad08fd11588c45698f7e63ecc3218a749fc8ca67 100644
> > > > > --- a/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > > > > +++ b/Documentation/devicetree/bindings/display/msm/dp-controller.yaml
> > > > > @@ -18,6 +18,7 @@ properties:
> > > > >      compatible:
> > > > >        oneOf:
> > > > >          - enum:
> > > > > +          - qcom,qcs8300-dp
> > > > 
> > > > Can we use fallback to qcom,sa8775p-dp instead of declaring a completely
> > > > new one?
> > > > 
> > > I think we can not use fallback to sa8775p, since we don't have DP1
> > > controller for QCS8300. SA8775P actually have 4 DP controllers (now only 2
> > > really used). So in the hardware, i think it is different with SA8775P and
> > > we need a new one.>>             - qcom,sa8775p-dp
> > 
> > The DP controller is the same as the one present on SA8775P.
> > 
> Yes, it is same.. I just want to confirm again—even if we only need DP0 for
> QCS8300, we can also use sa8775p as fallback, right?

What makes you think that we can't? Let me repharse the question: which
part of DP controller (single one) on QCS8300 is incompatible with the
DP controller on SA8775P?

> 
> static const struct msm_dp_desc msm_dp_desc_sa8775p[] = {
>     { .io_start = 0x0af54000, .id = MSM_DP_CONTROLLER_0, .wide_bus_supported
> = true },
>     { .io_start = 0x0af5c000, .id = MSM_DP_CONTROLLER_1, .wide_bus_supported
> = true },
>     { .io_start = 0x22154000, .id = MSM_DP_CONTROLLER_2, .wide_bus_supported
> = true },
>     { .io_start = 0x2215c000, .id = MSM_DP_CONTROLLER_3, .wide_bus_supported
> = true },
>     {}
> };
> .mst_streams = 4 is suitable for both QCS8300 and SA8775P DP 0 here.
> 
> Previously, my understanding here was that we might need a new compatible
> for QCS8300.
> 
> Thanks~~>>>>              - qcom,sc7180-dp
> > > > >              - qcom,sc7280-dp
> > 
> 

-- 
With best wishes
Dmitry