It was suggested to me that I should try out the radeonsi mesa driver due to the performance problems I am having in wine with fglrx (native stuff runs quite well with fglrx I have found so far) on my Radeon HD 7850 1GB card. I decided to go with the following, built from the master branches as of last night: mesa git, glamor git, xf86-video-ati git, llvm git, libtxc_dxtn git, kernel 3.10-rc2, xorg-server-1.12.2 - not necessarily built in that order of course.
What I found was that some steam titles ran, but not all of them (as an example, Half Life ran ok, but Portal crashes on the loading screen). What really perplexes me however is that running Skyrim on wine (runs fine with fglrx, just a little laggy in comparison to Windows driver) now crashes the whole X server, and makes my card kick out the message "couldn't schedule ib" repeatedly - bizarrely it runs fine on the title screen and loading screen, this only happens at the point where it would normally go to in-game.
Interestingly enough, I can also trigger this behaviour by changing the power management of the card from 'default' to 'high' with the sysfs interface. By default it seems to run at a clock speed equivalent to the 'low' setting.
I understand that given the raw state of radeonsi currently, there is probably not a lot more that I can do at this stage. I thought I would report my findings anyway however, in the hope that someone else may have a solution, or out of branch patches/tweaks that can help. I really appreciate the work that has gone into the open source graphics stack in general, so apologies if this sounds ungrateful - it is not meant that way. Any help/discussion is much appreciated and encouraged Many thanks.