On 6 August 2012 21:20, Kenneth Graunke <<a href="mailto:kenneth@whitecape.org" target="_blank">kenneth@whitecape.org</a>> wrote: <div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div class="HOEnZb"><div class="h5">On 08/05/2012 08:36 AM, Paul Berry wrote: > Just looking for a quick patch review to make sure I've backported > these patches to 8.0 correctly (and also confirmation that this > backport is a good idea). These patches are intended to apply to the > 8.0 branch. > > The issue is that on Gen6 and Gen7, images rendered to depth and > stencil buffers must be aligned to a multiple of 8 pixels, otherwise > certain rendering operations produce a GPU hang. Unfortunately, due > to the layout of miptrees (and the fact that we render to depth and > stencil miptrees using coordinate offsets), it would take a lot of > code rework to both produce correct rendering and guarantee no GPU > hangs. > > These patches avoid the GPU hangs by forcing the image offsets to be > multiples of 8. As a result, correct rendering to depth and stencil > miptrees is sacrificed but the GPU doesn't hang. The sacrifice is > minor, since it only affects miptree levels that would otherwise be > unaligned (in practice this is usually just the smallest miplevels), > and it only matters for (a) rendering to a depth/stencil buffer that > is later used as a texture, or (b) ping-ponging between miplevels > while rendering, both of which are fairly rare. On the master branch, > we decided that this was a worthwhile compromise. > > As a result of this sacrifice, this will regress the following piglit > tests: fbo/fbo-depth-array (Gen6 only), > spec/ARB_depth_buffer_float/fbo-clear-formats, > spec/ARB_depth_texture/fbo-clear-formats, and > spec/EXT_packed_depth_stencil/fbo-clear-formats. These tests > currently fail on master for the same reason. > > For more information see: > <a href="https://bugs.freedesktop.org/show_bug.cgi?id=50271" target="_blank">https://bugs.freedesktop.org/show_bug.cgi?id=50271</a> > > [PATCH 1/2] i965/Gen6: Work around GPU hangs due to misaligned depth coordinate offsets. > [PATCH 2/2] i965/Gen7: Work around GPU hangs due to misaligned depth coordinate offsets. </div></div>This trade-off makes sense to me. Take small amounts of misrendering in a few piglit tests doing non-real-world cases but avoid nasty GPU hangs. I hate to regress Piglit tests on stable, but it's for the best. </blockquote><div> Ok, cool. Thanks for the confirmation that this is a good idea. I hate doing cherry-picks to stable that have merge conflicts anyhow, and in this case the fact that it would cause known regressions made it seem even less certain--but I couldn't think of a better alternative. I'll plan on pushing it to stable tomorrow. </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> For some reason, I thought this needed the more invasive coarse/fine-grained tile offset patches. Have you tested this to confirm it fixes the cases? </blockquote></div> Yes, I tested it on both Sandy Bridge and Ivy Bridge. (Believe it or not, I brought both with me to SIGGRAPH :))