linux-kernel - Re: [PATCH 00/16] Enable GPU with DVFS support on MediaTek SoCs

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Date:   Thu, 9 Feb 2023 17:11:23 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     matthias.bgg@...il.com, 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 00/16] Enable GPU with DVFS support on MediaTek SoCs

On Wed, Feb 8, 2023 at 6:45 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> We finally have working GPU DVFS on MediaTek SoCs.
> On Panfrost.
> For real.
> ...and the best part is that it's going upstream.
>
> In order to get GPU DVFS working, it was necessary to satisfy a
> specific constraint (which is different, depending on the SoC)
> between two regulators: GPU VCORE and GPU SRAM.
> This was done through adding the mtk-regulator-coupler driver,
> which transparently manages the voltage relation between these
> two vregs, hence completely eliminating the need to manage these
> regulators in the Panfrost driver; this solves the long standing
> issue with devfreq+opp tables not supporting managing voltages
> for two regulators per opp entry out of the box, due to which
> we never got GPU DVFS on those SoCs, often locking them out to
> a low GPU frequency.
>
> This changes. Right now!
>
> Tested on MT8192, MT8195 Chromebooks.
>
> This series depends on [1].
>
> [1]: https://lore.kernel.org/lkml/20230208103709.116896-1-angelogioacchino.delregno@collabora.com/

Whole series is

Tested-by: Chen-Yu Tsai <wenst@...omium.org>

Tested on MT8183 Juniper (Kukui-based device), MT8192 Hayato (Asurada-based),
and MT8195 Tomato (Cherry-based).

GPU probed. When running glmark-es2-drm, observed state transitions in
/sys/class/devfreq/13040000.gpu/trans_stat , as well as actual changes to
values for regulators and clocks.

Also observed that sometimes when glmark terminated, the GPU would not be
brought down to the lowest OPP.