TTM and AGP conflicts

[James Simmons]

> > Hi!
> >
> >        I updated the openchrome tree and while testing on the AGP system
> > discovered some interesting problems with the new TTM changes. The
> > problems center around the ttm_tt_[un]populate which I modeled after the
> > radeon and nouveau driver.
> >        First problem I noticed was on a AGP system that my ttm_tt_populate
> > function would oops. Tracking it down I found the problem was the
> > ttm_agp_tt_create calls ttm_tt_init instead of ttm_dma_tt_init so once my
> > ttm_tt_populate function would attempt to touch the dma_address it would
> > oops. The second issue is the assumption of the cast for struct ttm_tt in
> > both the populate and unpopulate function. For the AGP case the proper
> > case would be to ttm_agp_backend.
> >        At this point my assumption is the ttm_bo_move function has to be
> > rewritten to handle the AGP case to avoid calling ttm_tt_bind and in all
> > cases ttm_tt_bind needs to be avoided. Looking at the radeon and nouveau
> > drivers I don't see that testing happening. Am I just missing something?
> 
> Happens on AGP radeons as well:
> https://bugs.freedesktop.org/show_bug.cgi?id=43719

	So I'm not crazy, so this needs to be fixed. Here is what my 
understanding of the TTM layer is. My impression is that struct ttm_bo_driver
handles multiple domains, AGP, pcie etc and in each method you have to 
handle each specific domain you support. Also *move gives the impression of
moving between these different domains. 
	Where as for struct ttm_backend_func was more for allocating from
a specific domain. Also I never saw a clear way to handle multiple backends. 
For example my AGP systems can also do pci dma as well.