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

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Date:   Fri, 17 Feb 2023 22:45:24 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...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 22:44, Dmitry Baryshkov wrote:
> 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.
Sure! I spent so much time on this that I can't really tell what's obvious
and what's not anymore, heh.

Konrad
>