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

From: Peng Fan <[email-masked]>
Date: Mon, 2 Feb 2026 10:41:49 +0800

On Fri, Jan 30, 2026 at 10:09:46AM +0100, Alexander Stein wrote:
>Am Freitag, 30. Januar 2026, 09:41:31 CET schrieb [email-masked]:
>> From: Ming Qian <[email-masked]>
>> 
>> 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@60fps 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 <[email-masked]>
>> ---
>>  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?

G1 and BUS clk were already set as Overdrive frequency.

This change is to only upgrading G2 from 300M to 600M.

So if your question is should we downgrade all to Nominal mode, I think
no. The freq could be override in board dts, or adding a new dts
as arch/arm64/boot/dts/freescale/imx8mp-nominal.dtsi

Regards
Peng

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