linux-kernel - Re: [PATCH v4 00/19] Enable GPU with DVFS support on MediaTek SoCs

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Date:   Tue, 7 Mar 2023 10:37:15 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chen-Yu Tsai <wenst@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v4 00/19] Enable GPU with DVFS support on MediaTek SoCs

Il 07/03/23 10:27, Chen-Yu Tsai ha scritto:
> On Thu, Mar 2, 2023 at 7:28 PM Matthias Brugger <matthias.bgg@...il.com> wrote:
>> On 02/03/2023 11:11, Chen-Yu Tsai wrote:
>>> On Thu, Mar 2, 2023 at 6:10 PM AngeloGioacchino Del Regno
>>> <angelogioacchino.delregno@...labora.com> wrote:
>>>>
>>>> Il 02/03/23 10:36, Matthias Brugger ha scritto:
>>>>> Series looks good but from my understanding has a dependency on:
>>>>> [PATCH v4 00/12] Panfrost: Improve and add MediaTek SoCs support
>>>>> (https://lore.kernel.org/linux-mediatek/20230228102610.707605-1-angelogioacchino.delregno@collabora.com/)
>>>>>
>>>>> Did I get that right?
>>>>>
>>>>
>>>> Yes you got it right - without the mentioned series, this one will do nothing
>>>> at all (and will also fail binding checks, as the bindings are introduced in
>>>> that other series).
>>>
>>> Please also let me test them on MT8183 and MT8186 before merging them.
>>>
>>
>> Of course, I'll wait for your tested-by tags then.
>> Thanks for testing!
> 
> Tested-by: Chen-Yu Tsai <wenst@...omium.org>
> 
> on MT8183, MT8186, MT8192 and MT8195 Chromebooks.
> 
> BTW, Angelo, I see that Panfrost keeps the GPU regulator enabled, but
> the power domains, and thus the SRAM regulator, get powered off when
> the GPU is not in use. There doesn't seem to be any damaging effects,
> but I worry about idle power consumption.
> 
> ChenYu

Yes I've seen that as well... and it's true there will be some unwanted
small power leakage.

Though, I would propose to do things step by step. Right now, as it is, the
platform is fully stable... so let's get this in so that we estabilish a
known working baseline... what I have in mind is, exactly:

1. Get Panfrost+DVFS working on current platforms; then
2. Resolve the GPU binning situation (eFuses -> opp-supported-hw)
3. Improve the power consumption (all GPU regulators off during suspend)

Thanks for all the valuable testing and support!

Cheers,
Angelo