Bug 23178

Created attachment 28401 [details]
Xorg.log

Description of problem:

The fix for bug #17235 and #19715 (git commit db9f5915) introduced a regression when changing resolution with xrandr with a VGA connected monitor on a Q43/Q45 chipset.

When switching resolution, the screen sometimes goes black and out of sync.

How reproducible:

It's fairly random and does not happen all the times. Roughly, I'd say it happens 75% of the time.

Steps to Reproduce:

1. Connect a monitor to the VGA port of a system with a Q43/Q45
2. Log in graphically
3. Use xrandr to select a lower resolution, e.g. xrandr -s "1024x768"
4. If that works, switch back to the original resolution, then select a
lower resolution again.

Actual results:

The screen goes black and shows "out of sync" message

Additional info:

A possible workaround is either to repeat the last xrandr command or to switch to a text console and back again.

The problem has been reported on the ML here:

  http://lists.freedesktop.org/archives/intel-gfx/2009-July/003419.html

"lspci" on the affected hardware gives:

  00:02.0 VGA compatible controller: Intel Corporation 4 Series Chipset
  Integrated Graphics Controller (rev 03) (prog-if 00 [VGA controller])
         Subsystem: Fujitsu Siemens Computers Unknown device 114c
         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- <TAbort- <MAbort- >SERR- <PERR-
         Latency: 0
         Interrupt: pin A routed to IRQ 11
         Region 0: Memory at fc000000 (64-bit, non-prefetchable) [size=4M]
         Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
         Region 4: I/O ports at 1c70 [size=8]
         Capabilities: [90] Message Signalled Interrupts: 64bit- Queue=0/0 Enable-
                 Address: 00000000  Data: 0000
         Capabilities: [d0] Power Management version 2
                 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                 Status: D0 PME-Enable- DSel=0 DScale=0 PME-