On Thu, Apr 10, 2014 at 10:32:46AM -0700, Ben Widawsky wrote: > On Thu, Apr 10, 2014 at 05:24:07PM +0100, Damien Lespiau wrote: > > While cruising through the specs, I noticed a note about swizzling changes on > > BDW. My understanding is that we don't need to either initialize swizzling on > > the GPU side nor swizzle the address ourselves on the CPU side. > > > > That could be totally wrong though, and I unfortunately don't have a machine to > > test this theory on. > > I fought with this too. My resolution was we can either set all the > swizzling bits, or set none. There is no motivation to do either, and > the spec simply is telling us what they do for windows. That was well > over a year ago, so it all can be different now. My (limited) understanding is telling me that if we don't return I915_BIT_6_SWIZZLE_NONE, user space is going to swizzle the address and the controller is going to swizzle it again, even from the CPU, so we end up at the wrong place. > I honestly don't care what we do though, so long as the patches get > tested both in simulation and silicon, and there is no measurable perf > drop. I suppose my mild preference is to, "don't touch it if it ain't > broke." > > Sorry, but at the moment, I don't have time to test this for you. Maybe > someone else can, or remind me in a couple of weeks. Do you know if you have a configuration where we try to swizzle? If yes and tests/gem_tiled_pread is passing that would give us a nice bit of information. (which of course can be tried by the next person with time to do so). -- Damien _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
