On 22 October 2013 10:07, Ian Romanick <i...@freedesktop.org> wrote: > On 10/21/2013 11:48 AM, Kenneth Graunke wrote: > > On 10/21/2013 08:40 AM, Ian Romanick wrote: > >> On 10/17/2013 11:09 PM, Kenneth Graunke wrote: > >>> Here's my implementation of ARB_transform_feedback2. I believe it's > >>> complete; it passes all of our Piglit tests and a lot of Intel's > >>> oglconform tests. > >>> > >>> This should work out of the box on Ivybridge and Baytrail. It won't > >>> work on Haswell at the moment, due to restrictions on register writes > >>> (to be solved in a future kernel version). Patch 9 will need to be > >>> replaced with something that detects whether or not we can write > >>> registers from userspace batchbuffers. > >>> > >>> In the meantime, I figured I'd send out the rest for review. > >>> > >>> Porting this back to Sandybridge is probably doable, but annoying. > >>> Sandybridge doesn't have the MI_LOAD_REGISTER_MEM command, so we'd have > >>> to map the buffers and use MI_LOAD_REGISTER_IMM. Seems pretty gross. > >>> Plus, transform feedback is done very differently pre-Ivybridge. I'm > >>> not sure it's worth it, seeing as it's a GL 4.0 feature. > >> > >> I assume this is just to support glDrawTransformFeedback? > > > > No, it's to support glResumeTransformFeedback. > > This is also part of OpenGL ES 3.0, so we need to fix it. :( >
Wow, you're right. For some reason I had convinced myself that OpenGL ES 3.0 didn't support BindTransformFeedback(), therefore it didn't have to support switching transform feedback objects while paused. But I just checked the spec and I was totally wrong about that. So yeah, we need to fix this even for Sandy Bridge. > > > glDrawTransformFeedback actually just reads pipeline statistics counters > > and leaves them free-running. > > > >> Can you add that information to > http://dri.freedesktop.org/wiki/I965Todo/ ? > > > > Actually, I'm probably wrong...on Gen7 we use MI_LOAD_REGISTER_MEM to > > copy offsets into the SO_WRITE_OFFSET(n) registers. But on Sandybridge, > > XFB is done using the geometry shader, so it works entirely differently. > > I don't think there is a register to load. > There is a register on Sandy Bridge, but instead of writing to it using MI_LOAD_REGISTER_*, you're supposed to write to it using 3DSTATE_GS_SVB_INDEX (see brw_begin_transform_feedback() in gen6_sol.c). That's kind of unfortunate for pause/resume because 3DSTATE_GS_SVB_INDEX doesn't support anything akin to MI_LOAD_REGISTER_MEM. It's possible that you can *also* write to those registers directly using MI_LOAD_REGISTER_MEM, but I haven't investigated that. > > > > I'll just let whoever looks into it figure it out. Not much insight > anyway. > > > > --Ken > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev >
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