linux-kernel - Re: [PATCH RFC RFT] drm/msm: adreno: attach the GMU device to a driver

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Message-ID: <c79c55fb-3aaa-4256-a71b-fa86cd0166f7@oss.qualcomm.com>
Date: Fri, 24 Oct 2025 10:55:00 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC RFT] drm/msm: adreno: attach the GMU device to a
 driver

On 10/23/25 10:27 AM, Neil Armstrong wrote:
> On 10/22/25 19:09, Konrad Dybcio wrote:
>> On 10/22/25 2:44 PM, Neil Armstrong wrote:
>>> Due to the sync_state is enabled by default in pmdomain & CCF since v6.17,
>>> the GCC and GPUCC sync_state would stay pending, leaving the resources in
>>> full performance:
>>> gcc-x1e80100 100000.clock-controller: sync_state() pending due to 3d6a000.gmu
>>> gpucc-x1e80100 3d90000.clock-controller: sync_state() pending due to 3d6a000.gmu
>>
>> Does this *actually* cause any harm, by the way?
> 
> ?
> 
>>
>> For example on x1e, GMU refers to 2 GPU_CC GDSCs, GPU_CC refers
>> to a pair of GCC clocks and GCC refers to VDD_CX
>>
>> and I see these prints, yet:
>>
>> /sys/kernel/debug/pm_genpd/gpu_cx_gdsc/current_state:off-0
>> /sys/kernel/debug/pm_genpd/gpu_gx_gdsc/current_state:off-0
>>
>> /sys/kernel/debug/pm_genpd/cx/current_state:on
>> /sys/kernel/debug/pm_genpd/cx/perf_state:256 # because of USB3 votes
>>
>> I'm not super sure where that sync_state comes from either (maybe
>> dev_set_drv_sync_state in pmdomain/core?)
> 
> The way we handle the GMU so far is wrong, it abuses the driver model.
> 
> And this is a symptom, whatever the impact it has, it needs to be fixed
> in a proper way.
> 
> The sync_state is retained because the gmu device is never probed but
> has some clocks and power domains attached to it, which is clearly wrong.

Yes I agree, however I'm only debating the commit message claims of
'leaving the resources in full performance', which doesn't seem to be
true

Konrad