mmu page fault on Odroid C2

titirez · December 22, 2023 at 9:12 AM

Hi,

I'm using latest LibreELEC 11.0.3 on my Odroid C2 and I have some issues. When playing music via the YouTube addon, my screen starts to show nasty artifacts and flickering. I see no errors in the Kodi log, however in dmesg I see this, every single time I start playing a song like this:

[ 140.927199] lima d00c0000.gpu: mmu page fault at 0x44d01c0 from bus id 0 of type read on ppmmu0
[ 140.927237] lima d00c0000.gpu: mmu page fault at 0x44d1040 from bus id 0 of type read on ppmmu1
[ 140.927250] lima d00c0000.gpu: mmu page fault at 0x44d01c0 from bus id 0 of type read on ppmmu2
[ 140.927679] lima d00c0000.gpu: pp task error 0 int_state=0 status=1
[ 140.927699] lima d00c0000.gpu: pp task error 1 int_state=0 status=1
[ 140.927709] lima d00c0000.gpu: pp task error 2 int_state=0 status=1
[ 140.927726] lima d00c0000.gpu: mmu resume

Here's the a full boot log:

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I really don't know where to start debugging this. I've spent some time reproducing this and looking into kodi log, but with or without debug info, I still don't see any errors there. So this mmu page fault error seems to indicate there is a kernel bug somewhere.

Anyone care to help with this ? Maybe it's an obvious thing like "Oh we don't support Odroid C2 anymore since LibreELEC vX" or whatever, but at least something.

**chewitt** · December 22, 2023 at 5:21 PM

The "lima" driver is responsible for 2D graphics (the Kodi GUI) rendering. Do you have a visualiser running while music is playing?

If yes, disable it or change it and see if that makes any difference?

You can also update to https://chewitt.libreelec.tv/testing/LibreE…h64-11.80.0.tar which has newer kernel (so newer lima driver) + newer mesa + newer Kodi .. will be LE12 once Kodi moves to RC and we can release a formal beta. Newer is not always better, but newer is different, so we can see if it influences the outcome.

NB: I also have no idea how to debug this

titirez · December 28, 2023 at 10:34 PM

Thanks for the reply,

So the visualisation in Settings / Player / Music / Visualisation is set to None.

The de facto visualization with the Youtube plugin is the Album cover art as displayed in YT Music phone app. But this is what triggers the artifacts and glitches.

If I configure the Youtube addon to play media "Audio Only" then I only get a "Youtube" written as static visualisation instead of the album art as before and nothing nasty happens, all seems good.

I guess I will try to use the image you provided to see if newer kernel and newer drivers improves things.

**chewitt** · December 29, 2023 at 6:31 AM

Kodi provides instructions to draw shapes on-screen using OpenGLES and these instructions are translated by mesa into "jobs" that are scheduled and executed on the GPU cores through the lima driver. The non-exhaustive list of possible opportunities for bugs are: a) Kodi sending bad GLES instructions to the DRM layer (mesa), or b) Kodi sending valid GLES that mesa incorrectly translates into jobs, or c) mesa sends valid jobs that the lima driver does not correctly handle during execution.

Changing the visualiser is "wagging the dogs tail to make the head move" and does not itself provide much of a clue where things go wrong. I need to see if I can resurrect the YouTube add-on (as it stopped working for me at some point and I switched to Tubed) to see if the issue exists on RPi5 too. If yes, it points to a Kodi issue as mesa effectively runs different code for the Mali 450 GPU in an S905 chip vs. the VideoCoreVII GPU in the RPi5, ergo a failure in both paths would be unusual and indicates something in Kodi-core or visualisation shader doing something wrong. If no (and I suspect it will be no) it's something lower in the stack and we'll need to capture debug job traces and share those with upstream maintainers to see if they can spot the problem.

NB: Testing on the LE12 image is useful as we're typically running the latest lima/mesa versions so we elimiate any bugs that have already been resolved since the older LE11 versions.

**chewitt** · December 29, 2023 at 8:37 AM

I got the YouTube add-on working again but I'm missing something to replicate the problem. All the "audio" content that I can find on YouTube also has video so I see normal video playback not audio with a visualiser. Can you share a link to something?