Bernardo Innocenti wrote: > Tom Sylla wrote: > >> http://openbios.org/viewvc/cpu/x86/pc/olpc/lxmsrs.fth?view=markup&revision=739&root=OpenFirmware >> has: >> msr: 0000.1810 fdfff000.fd000111. \ Video (write through), fbsize >> >> which is setting the framebuffer as write-combining. (the "write >> through" comment is incorrect) > > This takes care of the physical mapping, but how would userspace > be able to mmap the framebuffer into virtual memory without > additional MMU programming? > > I was under the impression that we also need to cover the whole > region with small 4KB MMU pages. This degrades performance > somewhat due to TLB misses when the CPU accesses the framebuffer. >
I missed whether or not the Geode actually has 4MiB huge pages, I thought someone said it does. This being the case, why can't you access the 16 (or was it 24?) MiB of memory via a handful (about 1/1024th) of huge mappings? Does x86 MMU not allow for huge MMIO? The Geode GX has 64 TLB entries right? I don't know how many the Geode LX has, or if there's an L2 TLB. Obviously, though, this would be a major performance boon, what with there being (assuming 24MiB of vram) 5 probably often used mappings instead of 5120 in an often-used set with a probably uneven distribution. > But I must confess I have limited understanding of the Geode > architecture, so I may be overlooking something. > -- Bring back the Firefox plushy! http://digg.com/linux_unix/Is_the_Firefox_plush_gone_for_good https://bugzilla.mozilla.org/show_bug.cgi?id=322367 _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel