Comment 109 for bug 148408

The 105_fdo_att7409_bug5437.diff (or upstream patch 8746) includes a workaround to figure out monitor specs (see bug #22985, a bug number I know by heart BTW). It involves doing VBE probing instead of the normal driver-asks-card probing. This workaround would break on some other cards/laptops, and was not needed any longer when the normal probing got fixed. The reason it makes VT switching working for you is probably a side effect. We can see this in your logs:
(WW) RADEON(0): zero MEMSIZE, probably at D3cold. Re-POSTing via int10.

Most likely it is the POST'ing that does the job. For resume, I think this can be configured in the sleep/resume settings. For VT switching, this must be done in the driver. Of course, there must be a better solution.