> Are you sure it uses PCI? I'm assuming that the destination address for > scratch writeback is controlled by the RADEON_SCRATCH_ADDR register. This > register is programmed to a value that falls within the AGP area (as > defined by RADEON_MC_AGP_LOCATION) if I understand the code correctly.
Ok, then that leads to another issue ... some AGP bridges simply don't support writes to AGP memory (or seem to support it but screw up). > > Hmm. The way RADEON_MC_(FB|AGP)_LOCATION are programmed, it seems to be like > they actually consist of two 16 bit fields, one indicating the start of the > FB/AGP area, the other indicating the end. Yup. > Do you know what happens when the programmed size of the FB area is larger > than the physical size of video RAM? What happens when the programmed size > of the AGP area is larger than the size of the AGP aperture? I don't know for sure, probably harmless though. What I know however is that we don't program it properly since we use CONFIG_APER_SIZE, which is the aperture size on PCI and has nothing to do with the actual amount of video memory on r100/200. I don't remember what we do on r300 except that we put it down to 0 which is wrong too. > > This problem has been fixed for plain Radeon drivers, but it could be > > that something similar is manifesting again on R300.. > > How did that fix work? Well, the "recommended" practice is to set MC_FB_LOCATION such that the framebuffer is at the same address in card's space as it's bus address from CPU viw, that is to whatever is in the BAR. (CONFIG_APER_BASE I suppose). Then to put AGP just after that (or before that if that doesn't fit). I think we do some of that for r100/r200 (though with the issue I describe above of using the wrong information for the size) and we just put the FB down at 0 for r300. Ben. ------------------------------------------------------- This SF.Net email is sponsored by: NEC IT Guy Games. How far can you shotput a projector? How fast can you ride your desk chair down the office luge track? If you want to score the big prize, get to know the little guy. Play to win an NEC 61" plasma display: http://www.necitguy.com/?r=20 -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
