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/sys/class/drm/card0/device/gpu_busy_percent always reports 100

Brief summary of the problem:

/sys/class/drm/card0/device/gpu_busy_percent always reports 100. I have never seen it reporting a different value, ever.

$ sudo cat /sys/class/drm/card0/device/gpu_busy_percent
100

I noticed this months ago (see for instance this issue I reported three months ago on CroeCtrl's repository).

My system is mostly idle most of the time:

$ sudo radeontop -d - -l1
Dumping to -, line limit 1.
1647208054.622845: bus 05, gpu 0.83%, ee 0.00%, vgt 0.00%, ta 0.00%, sx 0.00%, sh 0.00%, spi 0.00%, sc 0.83%, pa 0.00%, db 0.00%, cb 0.83%, vram 46.24% 925.28mb, gtt 3.44% 105.46mb, mclk 33.33% 0.400ghz, sclk 16.67% 0.200ghz

System description:

Hardware

  • Laptop: ThinkPad E495
  • CPU: AMD Ryzen 5 3500U with Radeon Vega Mobile Gfx
  • GPU: Picasso/Raven 2 [Radeon Vega Series / Radeon Vega Mobile Series] [1002:15D8], integrated in the CPU.

Software

  • Distro: Arch Linux, updated weekly. Issue has persisted for a long time (noticed it 3 months ago).
  • Kernel version: Linux tpe495 5.16.14-arch1-1 #1 SMP PREEMPT Fri, 11 Mar 2022 17:40:36 +0000 x86_64 GNU/Linux
    • Every kernel I tried in the past 3+ months (a number of linux, linux-lts and linux-zen) is affected.
  • AMD official driver version: xf86-video-amdgpu 22.0.0-1 and xf86-video-amdgpu 19.1.0-2
  • linux-firmware: currently 20220309.cd01f85-1. I tried a number due to this bug.