linux-kernel - Re: [PATCH 0/2] MT8195 Cherry: Assign MFG vregs for power saving

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Date:   Tue, 31 Oct 2023 14:16:57 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chen-Yu Tsai <wenst@...omium.org>
Cc:     matthias.bgg@...il.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH 0/2] MT8195 Cherry: Assign MFG vregs for power saving

Il 31/10/23 10:19, Chen-Yu Tsai ha scritto:
> On Mon, Oct 30, 2023 at 9:25 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> This series assigns the right regulators to MFG0 and MFG1, respectively
>> VGPU (GPU Core) and VSRAM_OTHERS (GPU SRAM), and removes the property
>> regulator-always-on from both.
>>
>> This allows to save power both during runtime suspend and during system
>> sleep; specifically because:
>>   1. The GPU SRAM regulator is switched off during runtime suspend
>>   2. The GPU Core regulator is switched off during system sleep
>>
>> Of course, in order for those power saving actions to actually take
>> place, it is required to also have the code in [1].
>> Anyway, even without series [1], this will not introduce any unstability
>> as the Vgpu regulator will simply not ever get turned off.
>>
>> [1]: https://lore.kernel.org/r/20231030132257.85379-1-angelogioacchino.delregno@collabora.com
>>
>> AngeloGioacchino Del Regno (2):
>>    arm64: dts: mediatek: mt8195-cherry: Add MFG0 domain supply
>>    arm64: dts: mediatek: mt8195-cherry: Assign sram supply to MFG1 pd
> 
> Tested-by: Chen-Yu Tsai <wenst@...omium.org>
> 
> on Tomato without the power saving patches. Regulators are correctly
> requested and I can see the SRAM regulator get turned on and off with
> GPU usage.

Yes, I confirm that the sram vreg going on/off is expected even without the power
saving patches (as the power domain refcount decreases during runtime suspend).

Thanks!

Angelo