linux-kernel - Re: [PATCH] arm64: dts: imx8mq: Set the correct gpu

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Message-ID: <aXkC/gVUk/lA2vzq@lizhi-Precision-Tower-5810>
Date: Tue, 27 Jan 2026 13:25:02 -0500
From: Frank Li <Frank.li@....com>
To: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>,
	Conor Dooley <conor@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, kernel@...i.sm
Subject: Re: [PATCH] arm64: dts: imx8mq: Set the correct gpu_ahb clock
 frequency

On Mon, Jan 26, 2026 at 09:10:37PM +0100, Sebastian Krzyszkowiak wrote:
> On poniedziałek, 26 stycznia 2026 19:14:55 czas środkowoeuropejski standardowy
> Frank Li wrote:
> > On Sat, Jan 24, 2026 at 02:55:48PM +0100, Sebastian Krzyszkowiak wrote:
> > > According to i.MX 8M Quad Reference Manual, GPU_AHB_CLK_ROOT's maximum
> > > frequency is 400MHz.
> >
> > I checked datasheet
> >
> > Nominal mode—the maximum
> > GPU frequency supported in
> > this mode is 800 MHz.
> >
> > Does difference grade (industry vs consumer) impact max frequency?
>
> No. That sentence relates to GPU_SHADER_CLK_ROOT, which can go up to 1000 MHz,
> but requires "overdrive mode" (higher voltage) when above 800 MHz. It's set to
> 800 MHz in the device tree at the moment.
>
> This patch changes GPU_AHB_CLK_ROOT, which has absolute maximum of 400 MHz
> (see section 5.1.2 Table 5-1).

Yes!

Reviewed-by: Frank Li <Frank.Li@....com>
>
> > Frank
> >
> > > Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
> > > ---
> > >
> > >  arch/arm64/boot/dts/freescale/imx8mq.dtsi | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > > b/arch/arm64/boot/dts/freescale/imx8mq.dtsi index
> > > 607962f807be..6a25e219832c 100644
> > > --- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > > +++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > > @@ -1632,7 +1632,7 @@ gpu: gpu@...00000 {
> > >
> > >  			                         <&clk
> IMX8MQ_GPU_PLL_OUT>,
> > >  			                         <&clk
> IMX8MQ_GPU_PLL>;
> > >
> > >  			assigned-clock-rates = <800000000>,
> <800000000>,
> > >
> > > -			                       <800000000>,
> <800000000>, <0>;
> > > +			                       <800000000>,
> <400000000>, <0>;
> > >
> > >  			power-domains = <&pgc_gpu>;
> > >
> > >  		};
> > >
> > > ---
> > > base-commit: 24d479d26b25bce5faea3ddd9fa8f3a6c3129ea7
> > > change-id: 20260105-imx8mq-gpu-ahb-clock-139ba9ca9a6c
> > >
> > > Best regards,
> > > --
> > > Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
>
>
>
>