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

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Message-ID: <20250905-indigo-mastiff-of-aptitude-b89e0a@kuoka>
Date: Fri, 5 Sep 2025 10:25:51 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Yongxing Mou <yongxing.mou@....qualcomm.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
	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 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

I don't understand how this rationale explains what Dmitry asked.

Why number of IP blocks (and this is DPx, right?) matter? Are you sure
you understand what compatibility means? Please read the slides from
OSSE25 or just read writing bindings.

Best regards,
Krzysztof