linux-kernel - Re: [PATCH v2 4/7] drm/panfrost: Add support for a second regulator for the GPU

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Message-ID: <20200108132302.GA3817@sirena.org.uk>
Date:   Wed, 8 Jan 2020 13:23:02 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Nicolas Boichat <drinkcat@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, hsinyi@...omium.org
Subject: Re: [PATCH v2 4/7] drm/panfrost: Add support for a second regulator
 for the GPU

On Wed, Jan 08, 2020 at 01:23:34PM +0800, Nicolas Boichat wrote:

> Some GPUs, namely, the bifrost/g72 part on MT8183, have a second
> regulator for their SRAM, let's add support for that.

> +	pfdev->regulator_sram = devm_regulator_get_optional(pfdev->dev, "sram");
> +	if (IS_ERR(pfdev->regulator_sram)) {

This supply is required for the devices that need it so I'd therefore
expect the driver to request the supply non-optionally based on the
compatible string rather than just hoping that a missing regulator isn't
important.  Though I do have to wonder given the lack of any active
management of the supply if this is *really* part of the GPU or if it's
more of a SoC thing, it's not clear what exactly adding this code is
achieving.

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