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

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Message-ID: <8657865.DvuYhMxLoT@pliszka>
Date: Mon, 26 Jan 2026 21:10:37 +0100
From: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
To: Frank Li <Frank.li@....com>
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 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).

> 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>