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References: <20240304-pinephone-pll-fixes-v3-0-94ab828f269a@oltmanns.dev> <20240304-pinephone-pll-fixes-v3-5-94ab828f269a@oltmanns.dev>
In-Reply-To: <20240304-pinephone-pll-fixes-v3-5-94ab828f269a@oltmanns.dev>
From: Erico Nunes <nunes.erico@gmail.com>
Date: Wed, 6 Mar 2024 16:04:47 +0100
Message-ID: <CAK4VdL0zWRg4hzUbuZsnabU53x3DrOiemH0tGnpbK9ECQvM1qg@mail.gmail.com>
Subject: Re: [PATCH v3 5/5] arm64: dts: allwinner: a64: Run GPU at 432 MHz
To: Frank Oltmanns <frank@oltmanns.dev>
Cc: Michael Turquette <mturquette@baylibre.com>, Stephen Boyd <sboyd@kernel.org>, 
	Chen-Yu Tsai <wens@csie.org>, Jernej Skrabec <jernej.skrabec@gmail.com>, 
	Samuel Holland <samuel@sholland.org>, =?UTF-8?Q?Guido_G=C3=BCnther?= <agx@sigxcpu.org>, 
	Purism Kernel Team <kernel@puri.sm>, Ondrej Jirman <megi@xff.cz>, Neil Armstrong <neil.armstrong@linaro.org>, 
	Jessica Zhang <quic_jesszhan@quicinc.com>, Sam Ravnborg <sam@ravnborg.org>, 
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, 
	Thomas Zimmermann <tzimmermann@suse.de>, David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
	Rob Herring <robh+dt@kernel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, 
	linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org, 
	linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, 
	dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org
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On Mon, Mar 4, 2024 at 6:01=E2=80=AFPM Frank Oltmanns <frank@oltmanns.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@gmail.com>

Thanks

Erico