On Mon, May 11, 2020 at 4:25 PM Rui Salvaterra <rsalvate...@gmail.com> wrote: > > > > A segunda, 11/05/2020, 21:21, Alex Deucher <alexdeuc...@gmail.com> escreveu: >> >> >> >> Note there is no loss of functionality here, at least on radeon >> hardware. It just comes down to which MMU gets used for access to >> system memory, the AGP MMU on the chipset or the MMU built into the >> GPU. On powerpc hardware, AGP has been particularly unstable, and >> IIRC, AGP has been disabled by default on radeon on powerpc for a >> while. > > > So this basically just drops support for the AGP GART? What happens to the > AGP signalling rates (beyond the base rate)?
I don't remember enough of the details, but I strongly doubt it was related to which MMU was used per se. On r1xx/r2xx parts, AGP was effectively the non-snooped route to memory and the internal MMU only provided snooped (coherent) access to memory. That and the limited TLB space are probably want limited performance in that case. I don't recall what sort of TLBs the chipset GART tables provided. On r3xx and newer the, on-chip MMU supported both snooped and unsnooped transactions and had more TLB space so the difference wasn't significant IIRC. Alex _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
