With the latest ati_1.0 combined with X7.0 and drm 1.19 from 2.6.15 that is in ubuntu dapper the situation has improved for VT switches and suspend/hibernation along with DRI on an X600 card. However one scenario still locks up the box (but sometimes it's just Xorg spinning). This is when restarting the server either by a new startx or by logout to the display manager. This shuts down the whole DRI stack and possibly leaves it in a different state than it was before starting X. When the machine does not lock up entirely, I can see via ssh/gdb that X is spinning in CP initialization and from drm debug=1 and dmesg that the kernel keeps returning EBUSY from the ioctl. If there's any more info I can provide (radeontool dumps, dmesg, xorg.log) or other things to try let me know. When radeon.ko is not found or I uncomment dri in xorg.conf all is well. Would trying a 2.6.17 kernel make sense?
a 2.6.16 or 2.6.17 might be worth a try, as benh's memmap kernel side changes aren't in 2.6.15, however I don't think his memmap DRM side changes should help a lot...
Tried latest stable 2.6.16.14 with radeon 1.22 in it and it works. This does not yet have the new memmap code so it must be something else that fixes my problem. The diff between 2.6.15 and 2.6.16 drm/radeon is not small though (dma and memory allocation differences, semaphore->mutex, some extra r300 specific bits, reworked init/teardown).
Dapper's kernel was updated to DRM 1.0.1 from 2.6.16 and the problem no longer appears.
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