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

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Message-ID: <36f62e69-ef7c-4f22-93ab-32bceade3fd1@linaro.org>
Date: Thu, 30 Oct 2025 11:02:55 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 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 10/30/25 10:52, Konrad Dybcio wrote:
> On 10/24/25 11:11 AM, Neil Armstrong wrote:
>> On 10/24/25 10:55, Konrad Dybcio wrote:
>>> 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
>>
>> OK so the wording may be a little bit extreme, perhaps something like:
>> the GCC and GPUCC sync_state would stay pending, leaving the unused
>> power domains enabled for the lifetime of the system.
> 
> The debugfs reads above suggest this is actually not happening

Oh yeah so let's do nothing, thanks for your very useful nitpick review.

Is there anyone going to review the actual change instead of the commit message wording ?

Neil

> 
> Konrad