> > 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.
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