linux-kernel - Re: [PATCH v2] clk: qcom: dispcc-sdm845: Enable parents for pixel clocks

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Message-ID: <d63d4c98-68f1-4dcb-b8fb-7c5daf343cc2@oss.qualcomm.com>
Date: Tue, 13 Jan 2026 15:50:06 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Val Packett <val@...kett.cool>, petr.hodina@...tonmail.com,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov
 <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd
 <sboyd@...nel.org>, David Heidelberg <david@...t.cz>,
        Taniya Das <quic_tdas@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, phone-devel@...r.kernel.org
Subject: Re: [PATCH v2] clk: qcom: dispcc-sdm845: Enable parents for pixel
 clocks

On 1/9/26 12:00 AM, Val Packett wrote:
> 
> On 1/7/26 8:44 AM, Petr Hodina via B4 Relay wrote:
>> From: Petr Hodina <petr.hodina@...tonmail.com>
>>
>> Add CLK_OPS_PARENT_ENABLE to MDSS pixel clock sources to ensure parent
>> clocks are enabled during clock operations, preventing potential
>> stability issues during display configuration.
>>
>> Fixes: 81351776c9fb ("clk: qcom: Add display clock controller driver for SDM845")
>> Signed-off-by: Petr Hodina <petr.hodina@...tonmail.com>
>> ---
>> We are currently running the latest linux-next snapshots (next-202511*
>> and next-202512*) and have encountered random freezes and crashes on the
>> Pixel 3, as well as crash dumps on the OnePlus 6 and 6T.
>>
>> This commit fixes the stability issue. I've checked other SDM dispcc
>> files and they also contain this configuration.
> 
> Hm, we don't have this flag set in dispcc-x1e80100.c either!
> 
> The only random freeze we have on that platform seems related to PCIe ASPM with NVMe drives, but during display configuration.. *extremely* rarely, but the eDP display output can get stuck on a blue screen. Many run with clk_ignore_unused for the early uefi framebuffer though.

Your device doesn't have a DSI-attached display

The Linux clock controller representation of the DSI PHY implements
an actually meaningful set of operations that (un)gate the clock

Both DP and eDP PHYs just provide funny fixed clocks to make the clock
tree resonable and filter allowed rates

Konrad