linux-kernel - Re: [PATCH v3] soc: mediatek: Introduce mediatek-regulator-coupler driver

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Date:   Tue, 13 Sep 2022 14:08:54 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     matthias.bgg@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, wenst@...omium.org,
        alyssa.rosenzweig@...labora.com, nfraprado@...labora.com,
        dmitry.osipenko@...labora.com
Subject: Re: [PATCH v3] soc: mediatek: Introduce mediatek-regulator-coupler
 driver

Il 28/06/22 14:02, AngeloGioacchino Del Regno ha scritto:
> This driver currently deals with GPU-SRAM regulator coupling, ensuring
> that the SRAM voltage is always between a specific range of distance to
> the GPU voltage, depending on the SoC, necessary in order to achieve
> system stability across the full range of supported GPU frequencies.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Reviewed-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

Hello Matthias,

gentle ping for this one, as it has been tested for quite a while here,
on multiple MediaTek SoCs, and it's working as expected.

Can we get it upstream? Is there any blocker?

Cheers,
Angelo

> ---
> 
> Changes in v3:
>   - Added braces to else-if branch
> 
> Changes in v2:
>   - Added check for n_coupled
>   - Added check for vgpu to enforce attaching to vgpu<->sram coupling only
> 
> Context:
> This driver is one of the pieces of a bigger puzzle, aiming to finally
> enable Dynamic Voltage/Frequency Scaling for Mali GPUs found on MediaTek
> SoCs on the fully open source graphics stack (Panfrost driver).
> 
> No devicetree bindings are provided because this does not require any
> driver-specific binding at all.
> 
> Last but not least: it was chosen to have this driver enabled for
> ( ARCH_MEDIATEK && REGULATOR ) without really giving a free configuration
> choice because, once the DVFS mechanism will be fully working, using one
> of the listed MediaTek SoCs *without* this coupling mechanism *will* lead
> to unstabilities and system crashes.
> For COMPILE_TEST, choice is given for obvious reasons.
>