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

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Message-ID: <25e829f8-60b2-4b69-8d57-ded846b5206a@linaro.org>
Date: Thu, 23 Oct 2025 10:27:26 +0200
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 10/22/25 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.

Neil

> 
> Konrad