linux-kernel - Re: [PATCH v2 03/14] drm/msm/a6xx: Introduce GMU wrapper support

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Message-ID: <aba38acf-d68f-27a8-eccc-f4a7b3b3535d@linaro.org>
Date:   Fri, 17 Feb 2023 23:44:02 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org
Cc:     marijn.suijten@...ainline.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Douglas Anderson <dianders@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/14] drm/msm/a6xx: Introduce GMU wrapper support

On 17/02/2023 23:41, Konrad Dybcio wrote:
> 
> 
> On 17.02.2023 22:37, Dmitry Baryshkov wrote:
>> On 14/02/2023 19:31, Konrad Dybcio wrote:
>>> Some (particularly SMD_RPM, a.k.a non-RPMh) SoCs implement A6XX GPUs
>>> but don't implement the associated GMUs. This is due to the fact that
>>> the GMU directly pokes at RPMh. Sadly, this means we have to take care
>>> of enabling & scaling power rails, clocks and bandwidth ourselves.
>>>
>>> Reuse existing Adreno-common code and modify the deeply-GMU-infused
>>> A6XX code to facilitate these GPUs. This involves if-ing out lots
>>> of GMU callbacks and introducing a new type of GMU - GMU wrapper.
>>> This is essentially a register region which is convenient to model
>>> as a device. We'll use it for managing the GDSCs.
>>
>> Why do you call it a wrapper?
> That's what Qualcomm calls it.. The GMU-less GPUs have (almost) all the
> same GMU GX/CX registers as the real GMUs in this 'wrapper' region, so
> that lets us reuse some code with gmu_(read/write/rmw) calls.
> 

Ack. If you can add this to the commit message, it would be great.

-- 
With best wishes
Dmitry