linux-kernel - Re: [PATCH RFC/WIP 0/4] arm64: dts: qcom: sm8750: Enable display

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Message-ID: <59cd28f3-f2a4-435d-9b13-3d56b1d1299c@gmail.com>
Date: Wed, 29 Oct 2025 23:59:07 -0700
From: Jessica Zhang <jesszhan0024@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Mahadevan P <mahadevan.p@....qualcomm.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 quic_rajeevny@...cinc.com
Cc: Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Abhinav Kumar <abhinavk@...cinc.com>,
 Abel Vesa <abel.vesa@...aro.org>, linux-arm-msm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC/WIP 0/4] arm64: dts: qcom: sm8750: Enable display

On 10/28/2025 11:27 PM, Krzysztof Kozlowski wrote:
> On 29/10/2025 07:20, Mahadevan P wrote:
>> Hi Krzysztof,
>>
>> On 4/26/2025 1:24 AM, Krzysztof Kozlowski wrote:
>>> On 25/04/2025 21:34, Dmitry Baryshkov wrote:
>>>> On Thu, Apr 24, 2025 at 03:04:24PM +0200, Krzysztof Kozlowski wrote:
>>>>> DTS is ready and I consider it ready for review, but still RFC because:
>>>>> 1. Display has unresolved issues which might result in change in
>>>>>      bindings (clock parents),
>>>>> 2. I did not test it since some time on my board...
>>>>> 3. Just want to share it fast to unblock any dependent work.
>>>>>
>>>>> DTS build dependencies - as in b4 deps, so:
>>>>> https://lore.kernel.org/r/20250421-sm8750_usb_master-v5-0-25c79ed01d02@oss.qualcomm.com/
>>>>> https://lore.kernel.org/r/20250424-sm8750-audio-part-2-v1-0-50133a0ec35f@linaro.org/
>>>>> https://lore.kernel.org/r/20250113-sm8750_gpmic_master-v1-2-ef45cf206979@quicinc.com/
>>>>>
>>>>> Bindings:
>>>>> 1. Panel:https://github.com/krzk/linux/tree/b4/sm8750-display-panel
>>>>> 2. MDSS:https://lore.kernel.org/r/20250311-b4-sm8750-display-v4-0-da6b3e959c76@linaro.org/
>>>>>
>>>>> Patchset based on next-20250424.
>>>> If the DisplayPort works on this platform, I'd kindly ask to send
>>>> separate DP+DPU only series (both driver and arm64/dts). It would make
>>>> it much easier (at least for me) to land the series, while you and
>>>> Qualcomm engineers are working on the DSI issues.
>>> DP has also issues - link training failures, although it feels as
>>> different one, because DSI issue Jessica narrowed to DSI PHY PLL VCO
>>> rate and I have a working display (just don't know how to actually solve
>>> this).
>>
>> We at Qualcomm are currently working on bringing up the DSI display on
>> MTP. For this, I’ve picked the following patches on top of |v6.18-rc2|:
> 
> Display on MTP8750 was fully brought already. I don't understand why you
> are doing the same.
> 
>>
>>   1. All the DT changes mentioned in this series
>>   2. [PATCH v2] drm/msm/dpu: Fix adjusted mode clock check for 3d merge
>>      https://lore.kernel.org/all/1154f275-f934-46ae-950a-209d31463525@kernel.org/
>>   3. [PATCH v2 0/2] drm/panel: Add Novatek NT37801 panel driver
>>      https://lore.kernel.org/all/20250508-sm8750-display-panel-v2-0-3ca072e3d1fa@linaro.org/
>>
>> However, when testing with |modetest|, the panel appears blank. I wanted
>> to check if there are any additional patches already posted that I might
>> have missed and should be included.
> 
> Many patches are missing because Qualcomm did not send them for months.
> I was pinging multiple times and I gave up - my job is not ping Qualcomm
> to send their patches.
> 
> I have no clue what you have already, what is your base, what errors you
> have and I will not be guessing this. For convenience, you can use my
> integration WIP branch from my github. I already shared that tree with
> Qualcomm more than once. Please reach internally first, instead of
> poking community.
> 
> 
>>
>> Also, I’m curious to understand more about the DSI PHY PLL VCO rate
>> issue that Jessica had narrowed down—could you please share some details?
> 
> Sorry, I am not going to repeat stuff done year ago. Please reach to the
> archives.

I don't have my notes on me, but IIRC this was the byte/pixel clk RCG 
failed to update issue that was causing the clocks to default to a bad 
rate (despite driver requesting the correct rate). It was fixed by this 
patch [1].

Thanks,

Jessica Zhang

[1] 
https://patchwork.kernel.org/project/linux-arm-msm/patch/20250520090741.45820-2-krzysztof.kozlowski@linaro.org/

> 
>>
>> Lastly, I’d appreciate it if you could share the plan for merging these
>> changes upstream.
> I don't understand what you ask me. Process of contributing to Linux
> kernel is well documented.
> 
> Best regards,
> Krzysztof