Eric Anholt (anholt) wrote,
Eric Anholt

This week in vc4 (2016-08-29): derivatives, GPU hangs, testing, kernel maintaining

I spent a day or so last week cleaning up @jonasarrow's demo patch for derivatives on vc4.  It had been hanging around on the github issue waiting for a rework due to feedback, and I decided to finally just go and do it.  It unfortunately involved totally rewriting their patches (which I dislike doing, it's always more awesome to have the original submitter get credit), but we now have dFdx()/dFdy() on Mesa master.

I also landed a fix for GPU hangs with 16 vertex attributes (4 or more vec4s, aka glsl-routing in piglit).  I'd been debugging this one for a while, and finally came up with an idea ("what if this FIFO here is a bad idea to use and we should be synchronous with this external unit?"), it worked, and a hardware developer confirmed that the fix was correct.  This one got a huge explanation comment.  I also fixed discards inside of if/loop statements -- generally discards get lowered out of ifs, but if it's in a non-unrolled loop we were doing discards ignoring whether the channel was in the loop.

Thanks to review from Rhys, I landed Mesa's Travis build fixes.  Rhys then used Travis to test out a couple of fixes to i915 and r600.  This is pretty cool, but it just makes me really want to get piglit into Travis so that we can get some actual integration testing in this process.

I got xserver's Travis to the point of running the unit tests, and one of them crashes on CI but not locally.  That's interesting.

The last GPU hang I have in piglit is in glsl-vs-loops.  This week I figured out what's going on, and I hope I'll be able to write about a fix next week.

Finally, I landed Stefan Wahren's Raspberry Pi Zero devicetree for upstream.  If nothing goes wrong, the Zero should be supported in 4.9.
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