[Bug 311895] [NEW] [i945] spontaneous black screen (major pipe-A underrun)

[Martin Pitt]

Public bug reported:

Binary package hint: xserver-xorg-video-intel

I am using a Dell Latitude D430 with an Intel GM945.

When I use my external 19" TFT (through DVI, 1280x1024), I occasionally
get a black screen. This is not triggered by anything obvious, it just
happens spontaneously. It is impossible to recover from this with
restarting X, only a reboot cures it.

Further investigation shows that this is caused by a long series of

  (EE) intel(0): underrun on pipe A!

errors (some 10.000 lines in the log). I get short underruns pretty
often, which results in the screen flickering for a split second, but
when the long series happens, the screen stays black forever.

A comparison of the intel_reg_dump output (-: works, +: black screen)
confirms this as well:

-(II):            PIPEASTAT: 0x00000203 (status: VSYNC_INT_STATUS VBLANK_INT_STATUS OREG_UPDATE_STATUS)
+(II):            PIPEASTAT: 0x80000000 (status: FIFO_UNDERRUN)

I have not observed this behaviour when I use the laptop undocked, with
the internal screen (1280x800).

This is current Jaunty with -intel 2:2.5.1-1ubuntu7. It also happened in
Intrepid, but back then I didn't know about intel_reg_dumper.

ProblemType: Bug
Architecture: i386
DistroRelease: Ubuntu 9.04
Package: xserver-xorg-video-intel 2:2.5.1-1ubuntu7
ProcEnviron:
 PATH: custom, user
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcVersion: Linux version 2.6.28-4-generic (buildd at palmer) (gcc version 4.3.3 20081217 (prerelease) (Ubuntu 4.3.2-2ubuntu9) ) #5-Ubuntu SMP Fri Dec 26 22:48:51 UTC 2008

SourcePackage: xserver-xorg-video-intel
Uname: Linux 2.6.28-4-generic i686
xkbcomp:

** Affects: xserver-xorg-video-intel (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-bug

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[i945] spontaneous black screen (major pipe-A underrun)
https://bugs.launchpad.net/bugs/311895
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