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

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Message-ID: <ca3a8042-1394-4925-9c61-dbfcbf4cf7d9@oss.nxp.com>
Date: Tue, 3 Feb 2026 15:13:21 +0800
From: "Ming Qian(OSS)" <ming.qian@....nxp.com>
To: Nicolas Dufresne <nicolas@...fresne.ca>, linux-media@...r.kernel.org
Cc: mchehab@...nel.org, hverkuil-cisco@...all.nl,
 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
Subject: Re: [PATCH] arm64: dts: imx8mq: Restore VPU G2 clock to 600MHz for
 4K60fps decoding

Hi Nicolas,

On 2/3/2026 3:12 AM, Nicolas Dufresne wrote:
> Hi,
> 
> Le lundi 02 février 2026 à 13:44 -0500, Nicolas Dufresne a écrit :
>>> This doesn't sound like just a VPU issue; it's related to the display or
>>> DDR.
>>> If not displayed, do the fluster test cases yield different results at
>>> 600MHz and 300MHz?
>>
>> Didn't you run these tests before sending ? I can try again, but in my
>> internal
>> notes, I wrote:
>>
>>    > Tested that, and everything becomes unstable
>>
>> That was before I figure-out the IRQ handler didn't handle exception bits that
>> didn't stop the decoder (or dry IRQ, which strangely is common from the G2).
> 
> Ran some fluster tests now. With this patch the results is not consistent
> anymore. Then I ran it with weston being started, and in the middle of the test
> the display turned black. Matches my past observation. We did reproduce this on
> BSP kernel too. When the display goes black, the recent hantro drivers reports:
> 
> [  827.581586] hantro-vpu 38310000.video-codec: frame decode timed out.
> [  827.720201] hantro-vpu 38310000.video-codec: not all macroblocks were
> decoded.
> 
> 
> I have local patches to reduce the cascade of errors, so it likely survived
> longer then last time. I will send these patches soon. The "not all macroblocks
> were decoded." is triggered by a bit in the status register that is not
> documented in NXP TRM. I found that bit in some VC8000D documentation (the
> sucessor of G2). I concluded it was the same meaning after looking at the failed
> buffer visually, it is indeed missing couple of macroblocks near th end. Each
> time we see this error, the DCSS gives up and turn either black, or sometimes
> other color. The second case has been tracked to a DCSS Scaler underrun, the
> first we don't know.
> 
> Fluster command ran (two threads, never completes):
> 
> ./fluster.py run -d GStreamer-H.265-V4L2SL-Gst1.0 -ts JCT-VC-HEVC_V1 -j2 -t90
> 
> Nicolas

My test results for fluster differ from yours.
On my end, the results for JCT-VC-HEVC_V1 are consistent at both 300MHz 
and 600MHz.
And results remained unchanged after multiple tests.

I'm not sure what caused the differences between us.

Below are my test results:

600Mhz, 0.9v
	cat /sys/kernel/debug/regulator/regulator_summary  |grep SW1C
	 SW1C                             0    1      0 unknown   900mV     0mA 
   825mV  1100mV
	cat /sys/kernel/debug/clk/vpu_g2/clk_rate
	600000000

	./fluster.py run -ts JCT-VC-HEVC_V1 -d GStreamer-H.265-V4L2SL-Gst1.0 
-j2 -t 90
	****************************************************************************************************
	Running test suite JCT-VC-HEVC_V1 with decoder 
GStreamer-H.265-V4L2SL-Gst1.0
	Using 2 parallel job(s)
	****************************************************************************************************

	Ran 139/147 tests successfully               in 505.434 secs
	Ran 139/147 tests successfully               in 505.350 secs
	Ran 139/147 tests successfully               in 507.540 secs

600Mhz, 1.0v
	cat /sys/kernel/debug/regulator/regulator_summary  |grep SW1C
	 SW1C                             0    1      0 unknown  1000mV     0mA 
   825mV  1100mV
	cat /sys/kernel/debug/clk/vpu_g2/clk_rate
	600000000

	./fluster.py run -ts JCT-VC-HEVC_V1 -d GStreamer-H.265-V4L2SL-Gst1.0 
-j2 -t 90
	Ran 139/147 tests successfully               in 506.901 secs

300Mhz, 0.9v
	cat /sys/kernel/debug/regulator/regulator_summary  |grep SW1C
	 SW1C                             0    1      0 unknown   900mV     0mA 
   825mV  1100mV
	cat /sys/kernel/debug/clk/vpu_g2/clk_rate
	300000000

	./fluster.py run -ts JCT-VC-HEVC_V1 -d GStreamer-H.265-V4L2SL-Gst1.0 
-j2 -t 90
	Ran 139/147 tests successfully               in 506.063 secs

Downstream v4l2 driver
	cat /sys/kernel/debug/regulator/regulator_summary  |grep SW1C
	 SW1C                             0    2      0 unknown  1000mV     0mA 
   825mV  1100mV
	cat /sys/kernel/debug/clk/vpu_g2/clk_rate
	600000000

	./fluster.py run -ts JCT-VC-HEVC_V1 -d GStreamer-H.265-V4L2-Gst1.0 -j2 
-t 90
	Ran 136/147 tests successfully               in 460.435 secs

Regards,
Ming