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Jarodiv
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PostPosted: Fri Jan 17, 2020 10:47 pm    Post subject: v3d MMU error from client L2T pte invalid Reply with quote

Hi everyone. To keep this post clean from distracting logs and details I decided to only post details on request. Please feel free to ask :)

I've build a 64-bit Gentoo on my Rpi4 (XFCE, Systemd), using the guides in the wiki and the image from Sakaki as a blueprint.

While in general everything seems to be working so far, I've even managed to get V3D support running (Mesa 19.3.2 with the V3D fix by Sakaki), there is one issue that I have absolutely no clue how to fix it and why seemingly only I am affekted by. When playing a video (doesn't if a file in VLC or on Youtube in Firefox) the screen goes black and my display reports "no signal". The only hint I got so far is a line in the logs (dmesg / journalctl) reading
Quote:
[ 63.211203] v3d fec00000.v3d: MMU error from client L2T (0) at 0xb4a1000, pte invalid


It seems, pretty obviously, to be an issue with v3d but googe didn't provide any help and comparing my setup with the work of Sakaki (which seems to not have the same issue) didn't reveal anything either. I already tried replacing my kernel+firmware+boot-config with the one from Sakakis image and also replaced my Mesa package with his (or her) binary but no effect at all.

Does anyone has experienced something similar and maybe even has an idea what the issue may be or at least where to look to get more details?
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Sakaki
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PostPosted: Sat Jan 18, 2020 8:19 pm    Post subject: Reply with quote

Hi Jarodiv,

not sure if it directly impacts your build (as I don't know the exact configuration of that) but, I always had problems with XVideo (Xv) playback on the RPi3/4, and so on my image this is disabled (forcing gl output instead).

Try placing the following in /usr/share/X11/xorg.conf.d/50-disable-Xv.conf (or, if you'd rather, in /etc/X11/xorg.conf.d/50-disable-Xv.conf):
Code:
# Xv currently crashes; use gl output for video instead
Section "Extensions"
   Option "XVideo" "Disable"
EndSection
and restarting.

Any more luck with video playback after that?
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sakaki
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Jarodiv
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PostPosted: Mon Jan 20, 2020 10:06 am    Post subject: Reply with quote

Sadly didn't change much. The screen still goes black (no signal) but the MMU warning has disappeared from the logs, leaving me with no hint at all (neither in /var/log/Xorg.0.log, nor in dmesg or journalctl).

Edit:
Just noticed something very interesting: While I am getting a black screen when using the micro HDMI port 1, it actually is working smoothly when using port 2. Only that there is no difference in the config for them in my /boot/config.txt
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Sakaki
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PostPosted: Mon Jan 20, 2020 10:22 am    Post subject: Reply with quote

Well, if that isn't it (although I think you will need this change for stable video playback), the issue is likely to lie either with the kernel / kernel config, the boot firmware, or mesa.

As you state the issue doesn't occur with the gentoo-on-rpi-64bit image, try temporarily swapping in my kernel (and module set) from there, and booting with that, keeping your boot firmware and userland the same.

And if that doesn't work, use the rest of /boot from my image (correcting /boot/cmdline.txt and /boot/config.txt as required).

If still not fixed, try installing mesa from the project's binhost too.
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Jarodiv
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PostPosted: Mon Jan 20, 2020 11:37 pm    Post subject: Reply with quote

I've already tried your Kernel+Firmware+Config and your binary for Mesa (19.3.2). I think I'll try my Kernel with your image to rule that out and also play around with combinations of your firmware + config and mine (likely next weekend),
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Sakaki
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PostPosted: Tue Jan 21, 2020 10:53 am    Post subject: Reply with quote

Hi Jarodiv,

oops I missed that you had mentioned you tried this in your original post, apologies (although, at that point was the xv fix applied too?) ><

As a further test to narrow things down, you could also try coming the other direction and booting my image, double-checking video playback works, and then chrooting into your userland (making sure to bind /dev etc. - see e.g. the instructions here, which are for chrooting into a 32-bit Raspbian userland, but the concepts are the same) and then running a video playback app from there.
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Jarodiv
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PostPosted: Sat Jan 25, 2020 3:53 pm    Post subject: Reply with quote

So today I had some time to further experiment. Here is what I did:

1. Boot my setup and play a video
-> Crashed into Black Screen (commandline still working) as expected

2. Boot into your setup and play a video
-> Worked as expected

3. Still booted in your setup, open a second commandline session, chroot into my setup, start XFCE on a different screen (-> "startxfce4 -- :1") and play a video
-> Worked (well ok, this got me confused a bit me since I already had booted your kernel without any success back then)

4. Boot my setup, open a second commandline session, chroot into your setup, start XFCE on a different screen and play a video
-> Worked (so it seems to has nothing to do with the kernel or the boot config)

5. Switch back to my XFCE session (not the one running in chroot) and play a video
-> Worked (this got me confused even more since in earlier attempts this setup didn't work)

6. Reboot (still my setup) and play a video (-> basically the exact same setup as in step 1)
-> Worked (now I got really confused since this didn't made any sense at all)

7. Wait some time and retry playing a video
-> Screen flickering but after some switches to black and back I got the desktop and the video was (still) playing

To be honest, I now am more confused than before. First of all, it seems like my setup generally is working. Strangely enough the flickering to black and back only happened the the first few times when I started a playback in step 7. Even after rebooting again the video playback now is working wihout having changed anything ¯\_(ツ)_/¯

I will do some further tests if this is influenced by CPU/system temperature, load or clock speed. For now it seems to be working (again, didn't change a thing) but I will wait with marking this as solved since I still expect the issue to come back.
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