Solved i915 / Xorg video problems

[tOsYZYny]

I moved my drives to a similar piece of hardware and am now having some issues with the video which could possibly be hardware-related. It is old equipment, the same age as the one it is replacing.

1. The first issue was that 1 display output was garbled, like the video cable wasn't seated.
2. After disconnecting the problematic monitor and leaving just one while the system was running, I saw some errors in the logs. To get the video working again, I unloaded and reloaded the driver, i915kms.

drmn0: [drm] *ERROR* uncleared fifo underrun on pipe A
drmn0: [drm] *ERROR* CPU pipe A FIFO underrun
drmn0: [drm] *ERROR* uncleared pch fifo underrun on pch transcoder A
drmn0: [drm] *ERROR* PCH transcoder A FIFO underrun
drmn0: [drm] *ERROR* uncleared fifo underrun on pipe A
drmn0: [drm] *ERROR* CPU pipe A FIFO underrun
drmn0: [drm] *ERROR* uncleared pch fifo underrun on pch transcoder A
drmn0: [drm] *ERROR* PCH transcoder A FIFO underrun
drmn0: [drm] *ERROR* [CRTC:45:pipe A] mismatch in pch_pfit.enabled 0xfffffe011c6ec7d0V
pipe state doesn't match!

3. When the system boots, there is no video output until i915kms is loaded. So, I have to blindly enter my password.

Right now, the system is running fine with a single monitor. I will try to troubleshoot some more and may go back to using a dedicated video card, like an nvidia.

How can I determine if this is a bug or hardware issue?

 

[Drdave]

im getting same error, although it doesnt appear to affect anything.

drmn0: [drm] *ERROR* uncleared pch fifo underrun on pch transcoder B
drmn0: [drm] *ERROR* PCH transcoder B FIFO underrun
It seems to have started when i installed kde5.
searching for the error on the net didn't turn up much....mostly linux kernel posts about it.

 

[tOsYZYny]

I haven't had this issue again. I still believe it is hardware-related, but I have since reimaged my machines and haven't had this.

Now, when watching videos, I routinely see frames dropped and underruns there, but I don't see these errors. As my machine is older and slower, I expect it to struggle to play HD+ videos as I'm using the onboard video. That said, KDE is more of a resource hog than i3, if you use a lighter DE and don't see those errors, then perhaps you can draw the conclusion that KDE is the culprit and merely needs more powerful hardware.

I marked the thread as resolved as I'm not seeing these errors any longer. If you're still having these errors after trying the above, please respond back and we can troubleshoot here.