Comment 9 for bug 513956

Forwarding this bug from Ubuntu reporter Jamie Strandboge:
http://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/513956

[Problem]
Due to bug #26302, KMS seems to be broken on this hardware, so we're considering blacklisting this pci id to use UMS. However, with UMS instead of KMS, the screen suffers corruption when compositing is used.

This might be the old "Random screen corruption with 3D on XAA", however it appears the driver is opting for XAA rather than EXA as the default in this circumstance so that seems suboptimal. The user also tried forcing the hardware to use EXA but found it resulted in unacceptably slow performance.

The only known stable configuration for the radeon 7500 is XAA/metacity/RenderAccel off/no KMS).

This has been tested against Ubuntu 2.6.32-16.24-generic which contains the 2.6.33 drm backported, as airlied recommended.

[Original Description]
In trying workarounds for LP bug #507148 (fdo #26302) I disabled KMS by booting with radeon.modeset=0. When I logged in compiz was enabled, but opening applications resulted in garbled parts of the screen. See attached screenshot.

Architecture: i386
Date: Thu Jan 28 13:52:56 2010
DistroRelease: Ubuntu 10.04
DkmsStatus: Error: [Errno 2] No such file or directory
EcryptfsInUse: Yes
Lsusb:
 Bus 004 Device 002: ID 0483:2016 SGS Thomson Microelectronics Fingerprint Reader
 Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: IBM 2378RRU
Package: xorg 1:7.5+1ubuntu2
PccardctlIdent:
 Socket 0:
   no product info available
 Socket 1:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
 Socket 1:
   no card
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-11-generic root=UUID=0c1cec18-6655-4ef5-8c03-2009d66c50e2 ro splash quiet radeon.modeset=0
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 ProcVersionSignature: Ubuntu 2.6.32-11.15-generic
RelatedPackageVersions:
 xserver-xorg 1:7.5+1ubuntu2
 libgl1-mesa-glx 7.7-0ubuntu8
 libdrm2 2.4.17-0ubuntu2
 xserver-xorg-video-intel 2:2.9.1-1ubuntu1
SourcePackage: xorg
Uname: Linux 2.6.32-11-generic i686
dmi.bios.date: 06/18/2007
dmi.bios.vendor: IBM
dmi.bios.version: 1RETDRWW (3.23 )
dmi.board.name: 2378RRU
dmi.board.vendor: IBM
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: IBM
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnIBM:bvr1RETDRWW(3.23):bd06/18/2007:svnIBM:pn2378RRU:pvrThinkPadT42:rvnIBM:rn2378RRU:rvrNotAvailable:cvnIBM:ct10:cvrNotAvailable:
dmi.product.name: 2378RRU
dmi.product.version: ThinkPad T42
dmi.sys.vendor: IBM
system:
  architecture: i686kernel: 2.6.32-11-generic

[lspci]
01:00.0 VGA compatible controller [0300]: ATI Technologies Inc Radeon Mobility M7 LW [Radeon Mobility 7500] [1002:4c57]
     Subsystem: IBM Device [1014:0530]