Created attachment 28401 [details]
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.
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.
The screen goes black and shows "out of sync" message
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:
"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-
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:  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-
Created attachment 28402 [details] [review]
Patch to unconditionally disable VGA plane
This patch seems to avoid the problem and the screen does not go out of sync.
Created attachment 28462 [details] [review]
new patch to disable vga plane
Olivier, could you test with patch to see if it fixes your problem?
Pushed the patch. Close.
Author: Zhenyu Wang <email@example.com>
Date: Tue Aug 18 10:01:12 2009 +0800
Fix VGA plane disabling
Only apply on G4X with SR01 bit5 workaround for VGA plane disable, and
restore behavior back for other chips to make sure other modes got disabled
For bug #17235, #19715, #21064, #23178
Signed-off-by: Zhenyu Wang <firstname.lastname@example.org>
However, this commit is not in current 2.8 branch:
whereas the patch was committed in that branch apparently:
Was there any reason for that patch not to be merged in 2.8?