On Thu, 16 Feb 2012 18:38:08 +0100, Daniel Vetter <dan...@ffwll.ch> wrote: > On Thu, Feb 16, 2012 at 08:48:07AM -0800, Eric Anholt wrote: > > On Thu, 16 Feb 2012 13:11:31 +0100, Daniel Vetter <daniel.vet...@ffwll.ch> > > wrote: > > > No longer needed. > > > > What this code was for: Before gtt mapping, we were doing software > > fallbacks in Mesa with pread/write on pages at a time (or worse) of the > > framebuffer. It would regularly result in hitting the same page again, > > since I was only caching the last page I'd pulled out, instead of > > keeping a whole copy of the framebuffer during the fallback. > > Urgh, that's not really efficient ;-) I think for s/w fallbacks and > readbacks we can presume decent damage tracking (like sna does) on the > userspace sides. > > > Since we've been doing gtt mapping for years at this point, I'm happy to > > see the code die. > > > > I'm not sure about the rest of the code. In particular, for the code > > that's switching between gtt and cpu mappings to handle a read/write, > > I'm concerned about whether the behavior matches for tiled objects. I > > haven't reviewed enough to be sure. > > Behaviour should match old code if you read/write entire pages (we should > have decent set of tests for that). If you do non-cacheline-aligned > reads/writes on tiled objects, we might hit an issue, but they should be > solveable (I've simply been too lazy to write testcases for this). Not > cacheline aligned reads/writes on untiled also work, I've created a set of > tests to exercise issues there (and tested the tests by omitting some of > the clflushes, i.e. all the clfushes now left _are_ required). > > If old mesa depends on sub-page reads/writes to tiled objects I need to > create the respective tests and double-check the code, otherwise I think > we're covered. Do you want me to adapt the tests to check correctness for > sub-page reads/writes to tiled objects?
In the long long ago, I believe we did per-pixel accesses of tiled objects through pread/pwrite. Crazy, I know.
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