[Bug 48053] AGP speed not detected properly causing black screen and unkillable Xorg process

[Bruce Milner]

Public bug reported:

Binary package hint: kernel-image-2.6.15-23-amd64-generic-di

After updating to dapper, I ended up with a black screen and a hung Xorg
process that I could not even force kill. Here is the error in the
syslog that seems relevant to this problem. The Xorg process was taking
all cpu.

---------------------------------------------------------------------------------------
[   64.049497] [drm] Initialized radeon 1.24.0 20060225 on minor 0
[   64.933205] agpgart: Found an AGP 3.5 compliant device at 0000:00:00.0.
[   64.933220] agpgart: Badness. Don't know which AGP mode to set. [bridge_agpstat:1f000a0a vga_agpstat:ff00021b fell back to:- bridge_agpstat:1f000208 vga_agpstat:ff00021b]
[   64.933223] agpgart: Bridge couldn't do AGP x4.
[   64.933229] agpgart: Putting AGP V3 device at 0000:00:00.0 into 0x mode
[   64.933281] agpgart: Putting AGP V3 device at 0000:01:00.0 into 0x mode

...

[   69.264076] [drm] Setting GART location based on new memory map
[   69.264087] [drm] Loading R300 Microcode
[   69.273656] [drm] writeback test failed
---------------------------------------------------------------------------------------

After doing net searches for similar problems, I ran across some
messages about unkillable xorg processes that stated that the AGP speed
was being detected incorrectly with newer kernels and some setups. After
changing my bios to 4X AGP instead of 8X AGP, xorg works again and the
following is the relevant output in the syslog. Note that the writeback
test fails above and works below. This system was running breezy just
fine before (2.6.12-10).

---------------------------------------------------------------------------------------
blue at crow:/root$ dmesg | grep agp
[   85.564568] agpgart: Detected AGP bridge 0
[   85.567727] agpgart: AGP aperture is 64M @ 0xf8000000
[   85.580437] Linux agpgart interface v0.101 (c) Dave Jones
[  115.076136] agpgart: Found an AGP 3.5 compliant device at 0000:00:00.0.
[  115.076153] agpgart: Putting AGP V3 device at 0000:00:00.0 into 4x mode
[  115.076206] agpgart: Putting AGP V3 device at 0000:01:00.0 into 4x mode
blue at crow:/root$ dmesg | grep drm
[  114.185322] [drm] Initialized drm 1.0.1 20051102
[  114.192610] [drm] Initialized radeon 1.24.0 20060225 on minor 0
[  119.407115] [drm] Setting GART location based on new memory map
[  119.407207] [drm] Loading R300 Microcode
[  119.407274] [drm] writeback test succeeded in 1 usecs
---------------------------------------------------------------------------------------

** Affects: linux-source-2.6.15 (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed

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AGP speed not detected properly causing black screen and unkillable Xorg process
https://launchpad.net/bugs/48053