linux-kernel - Re: [PATCH v3 5/5] arm64: dts: allwinner: a64: Run GPU at 432 MHz

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Message-ID: <CAK4VdL0zWRg4hzUbuZsnabU53x3DrOiemH0tGnpbK9ECQvM1qg@mail.gmail.com>
Date: Wed, 6 Mar 2024 16:04:47 +0100
From: Erico Nunes <nunes.erico@...il.com>
To: Frank Oltmanns <frank@...manns.dev>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Samuel Holland <samuel@...lland.org>, Guido Günther <agx@...xcpu.org>, 
	Purism Kernel Team <kernel@...i.sm>, Ondrej Jirman <megi@....cz>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 5/5] arm64: dts: allwinner: a64: Run GPU at 432 MHz

On Mon, Mar 4, 2024 at 6:01 PM Frank Oltmanns <frank@...manns.dev> wrote:
>
> The Allwinner A64's GPU has currently three operating points. However,
> the BSP runs the GPU fixed at 432 MHz. In addition, at least one of the
> devices using that SoC - the pinephone - shows unstabilities (see link)
> that can be circumvented by running the GPU at a fixed rate.
>
> Therefore, remove the other two operating points from the GPU OPP table,
> so that the GPU runs at a fixed rate of 432 MHz.

In addition to all of this, the A64 user manual does say explicitly
that "dynamic frequency scaling is not supported" on PLL_GPU. So I
think this is really needed for a reliable GPU experience on A64.

Acked-by: Erico Nunes <nunes.erico@...il.com>

Thanks

Erico