linux-kernel - Re: [PATCH v3 3/4] dt-bindings: display/msm: Document MDSS on QCS8300

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Message-ID: <2bafc177-b996-43ae-bd37-f095c9f16b62@kernel.org>
Date: Tue, 14 Jan 2025 12:19:54 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Yongxing Mou <quic_yongmou@...cinc.com>, Rob Clark <robdclark@...il.com>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 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>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>,
 Bjorn Andersson <andersson@...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,
 linux-phy@...ts.infradead.org
Subject: Re: [PATCH v3 3/4] dt-bindings: display/msm: Document MDSS on QCS8300

On 14/01/2025 12:09, Dmitry Baryshkov wrote:
> On Tue, Jan 14, 2025 at 11:11:23AM +0100, Krzysztof Kozlowski wrote:
>> On 14/01/2025 11:00, Dmitry Baryshkov wrote:
>>> On Tue, 14 Jan 2025 at 09:57, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>>>
>>>> On Mon, Jan 13, 2025 at 04:03:10PM +0800, Yongxing Mou wrote:
>>>>> +patternProperties:
>>>>> +  "^display-controller@[0-9a-f]+$":
>>>>> +    type: object
>>>>> +    additionalProperties: true
>>>>> +
>>>>> +    properties:
>>>>> +      compatible:
>>>>> +        items:
>>>>> +          - const: qcom,qcs8300-dpu
>>>>> +          - const: qcom,sa8775p-dpu
>>>>> +
>>>>> +  "^displayport-controller@[0-9a-f]+$":
>>>>> +    type: object
>>>>> +    additionalProperties: true
>>>>> +
>>>>> +    properties:
>>>>> +      compatible:
>>>>> +        items:
>>>>> +          - const: qcom,qcs8300-dp
>>>>> +          - const: qcom,sm8650-dp
>>>>
>>>> Parts of qcs8300 display are compatible with sa8775p, other parts with
>>>> sm8650. That's odd or even not correct. Assuming it is actually correct,
>>>> it deserves explanation in commit msg.
>>>
>>> It seems to be correct. These are two different IP blocks with
>>> different modifications. QCS8300's DP configuration matches the SM8650
>>> ([1]), though the DPU is the same as the one on the SA8775P platform.
>>>
>>> [1] https://lore.kernel.org/dri-devel/411626da-7563-48fb-ac7c-94f06e73e4b8@quicinc.com/
>>
>> That's the driver, so you claim that qcs8300, which is a sa8775p, is not
>> compatible with sa8775p because of current driver code? You see the
>> contradiction? sa8775p is not compatible with sa8775p because of current
>> driver patch?
> 
> I think you are slightly confused with different similar QCS SKUs here.
> QCS9100 is sa8775p. QCS8300 is a lighter version of it.


True, yet still qcs8300 derives from SA8775p:

https://lore.kernel.org/all/acdf1267-ce56-4ec1-8407-a5f3212a8bfe@quicinc.com/

Therefore my comment, that commit msg must explain why derivative
display is SA8775p-compatible in DPU part, but not in DP part, is still
valid.

Look how useful is commit msg here:

"Document the MDSS hardware found on the Qualcomm QCS8300 platform."

It says exactly what is in the diff. As well we could just skip it...

Best regards,
Krzysztof