KMS and Radeon RS880 (HD 4200)

[Godfrey Benitez]

I have an AMD 785G-based motherboard with built-in Radeon graphics identified by 
lspci as "ATI Technologies Inc RS880 [Radeon HD 4200]". I can easily get 
month-long uptimes when Kernel Mode Setting is disabled. However, when KMS is 
enabled, the screen locks within two days of running continuously, sometime even 
less. By lock, I mean the monitor turns black. The keyboard still appears 
responsive, I can toggle Num Lock and Caps Lock on and off,  and I can issue 
Ctrl-Alt-Delete to reboot the computer.

The bug appears to be randomly triggered. It has happened while I am running 
widely different programs like Firefox and Abiword. (Surprisingly, the bug has 
yet to happen when I'm playing a presumably graphics-intensive 3D game like 
Glest). Interestingly, however, the bug happens more frequently (it happens 
faster) when I choose to reboot the computer (hot restart) rather than shut it 
down and then turn it back on (cold start).

The kernel log (kern.log) shows a string of error messages that begins (trimmed 
to avoid spamming the list):


Jul 14 16:45:19 localhost kernel: [121762.072083] [drm:radeon_fence_wait] 
*ERROR* fence(ffff880076f71a40:0x0130ECFB) 504ms timeout going to reset GPU
Jul 14 16:45:19 localhost kernel: [121762.072096] radeon 0000:01:05.0: GPU 
softreset 
Jul 14 16:45:19 localhost kernel: [121762.072101] radeon 0000:01:05.0:   
R_008010_GRBM_STATUS=0xA27334AC
Jul 14 16:45:19 localhost kernel: [121762.072107] radeon 0000:01:05.0:   
R_008014_GRBM_STATUS2=0x00000103
Jul 14 16:45:19 localhost kernel: [121762.072112] radeon 0000:01:05.0:   
R_000E50_SRBM_STATUS=0x20001040
Jul 14 16:45:19 localhost kernel: [121762.072122] radeon 0000:01:05.0:   
R_008020_GRBM_SOFT_RESET=0x00007FEE
Jul 14 16:45:19 localhost kernel: [121762.072178] radeon 0000:01:05.0: 
R_008020_GRBM_SOFT_RESET=0x00000001
Jul 14 16:45:19 localhost kernel: [121762.072236] radeon 0000:01:05.0:   
R_000E60_SRBM_SOFT_RESET=0x00000402
Jul 14 16:45:19 localhost kernel: [121762.072392] radeon 0000:01:05.0:   
R_008010_GRBM_STATUS=0x00003030
Jul 14 16:45:19 localhost kernel: [121762.072397] radeon 0000:01:05.0:   
R_008014_GRBM_STATUS2=0x00000003
Jul 14 16:45:19 localhost kernel: [121762.072402] radeon 0000:01:05.0:   
R_000E50_SRBM_STATUS=0x20000040
Jul 14 16:45:19 localhost kernel: [121762.073802] [drm:radeon_fence_wait] 
*ERROR* fence(ffff880076f71a40:0x0130ECFB) 512ms timeout
Jul 14 16:45:19 localhost kernel: [121762.073807] [drm:radeon_fence_wait] 
*ERROR* last signaled fence(0x0130ECFB)
Jul 14 16:45:19 localhost kernel: [121762.084131] [drm:radeon_fence_wait] 
*ERROR* fence(ffff8800761de540:0x0130ECFC) 512ms timeout going to reset GPU
Jul 14 16:45:19 localhost kernel: [121762.084142] radeon 0000:01:05.0: GPU 
softreset 

On the other hand, dmesg shows nothing suspicious other than the initial 
confirmation that KMS is enabled:

[    5.242464] [drm] radeon kernel modesetting enabled.
[    5.242554] radeon 0000:01:05.0: PCI INT A -> GSI 18 (level, low) -> IRQ 18
[    5.242558] radeon 0000:01:05.0: setting latency timer to 64
[    5.244309] [drm] radeon: Initializing kernel modesetting.

I'm running Linux 2.6.32-5 (AMD64) with Xorg 7.5, Radeon driver 6.13.1, and DRM 
driver 2.4.18.