linux-kernel - Re: [PATCH] arm64: dts: imx8mq: Restore VPU G2 clock to 600MHz for 4K60fps decoding

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Message-ID: <5476502.mvXUDI8C0e@steina-w>
Date: Fri, 30 Jan 2026 10:09:46 +0100
From: Alexander Stein <alexander.stein@...tq-group.com>
To: linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: mchehab@...nel.org, hverkuil-cisco@...all.nl, nicolas@...fresne.ca,
 benjamin.gaignard@...labora.com, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, p.zabel@...gutronix.de, sebastian.fricke@...labora.com,
 shawnguo@...nel.org, ulf.hansson@...aro.org, s.hauer@...gutronix.de,
 kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
 l.stach@...gutronix.de, Frank.li@....com, peng.fan@....com,
 eagle.zhou@....com, devicetree@...r.kernel.org, imx@...ts.linux.dev,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, ming.qian@....nxp.com
Subject:
 Re: [PATCH] arm64: dts: imx8mq: Restore VPU G2 clock to 600MHz for 4K60fps
 decoding

Am Freitag, 30. Januar 2026, 09:41:31 CET schrieb ming.qian@....nxp.com:
> From: Ming Qian <ming.qian@....nxp.com>
> 
> The VPU G2 clock was reduced from 600MHz to 300MHz in commit
> b27bfc5103c7 ("arm64: dts: freescale: Fix VPU G2 clock") to address
> pixel errors with high-resolution HEVC postprocessor output.
> 
> However, testing shows the 300MHz clock rate is insufficient for
> 4K60fps decoding and the original pixel errors no longer occur at
> 600MHz with current drivers.
> 
> Test results with 3840x2160@...ps HEVC stream decoded to NV12
> (the same scenario that exhibited pixel errors previously):
> 
> 300MHz performance:
> - Severe frame dropping throughout playback
> - Only 336 frames rendered in 11:53 (0.471 fps)
> - Continuous "A lot of buffers are being dropped" warnings
> - Completely unusable for 4K video
> 
> 600MHz performance:
> - Smooth playback with only 1 frame dropped at startup
> - 37981 frames rendered in 10:34 (59.857 fps)
> - Achieves target 60fps performance
> - No pixel errors or artifacts observed
> 
> Restore the clock to 600MHz to enable proper 4K60fps decoding
> capability while maintaining stability.
> 
> Test pipeline:
>   gst-launch-1.0 filesrc location=<4K60_HEVC.mkv> ! \
>     video/x-matroska ! aiurdemux ! h265parse ! \
>     v4l2slh265dec ! video/x-raw,format=NV12 ! \
>     queue ! waylandsink
> 
> Fixes: b27bfc5103c7 ("arm64: dts: freescale: Fix VPU G2 clock")
> Signed-off-by: Ming Qian <ming.qian@....nxp.com>
> ---
>  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..731142176625 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> @@ -960,7 +960,7 @@ pgc_vpu: power-domain@6 {
>  									 <&clk IMX8MQ_SYS1_PLL_800M>,
>  									 <&clk IMX8MQ_VPU_PLL>;
>  						assigned-clock-rates = <600000000>,
> -								       <300000000>,
> +								       <600000000>,

If I read the Datasheet correctly 600 MHz is only supported by overdrive
mode (also depending on the VDD_VPU).
Is this frequency really correct?

Best regards,
Alexander

>  								       <800000000>,
>  								       <0>;
>  					};
> 
> base-commit: c824345288d11e269ce41b36c105715bc2286050
> prerequisite-patch-id: 0000000000000000000000000000000000000000
>