[Bug 96743] [BYT, HSW, SKL, BXT, KBL] GPU hangs with GfxBench 4.0 CarChase

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Mar 13 07:46:49 UTC 2017


https://bugs.freedesktop.org/show_bug.cgi?id=96743

--- Comment #15 from Topi Pohjolainen <topi.pohjolainen at intel.com> ---
I still haven't reached the root cause but having tried various things I
thought better listing down some possibly interesting bits:

1) Making clears a no-op gives me a hang in L3 cache reconfig (see
gen7_l3_state.c::setup_l3_config()). Specifically in the register write:
MI_LOAD_REGISTER_IMM.

2) Making the L3 cache reconfig a no-op in turn moves the hang into compute
pipeline (carchase also renders some bits using GPGPU). There it hits the
second flush issued by intel_fbo.c::brw_render_cache_set_check_flush().

3) Here I started reading specs again and found a bit we are currently ignoring
in  few places. SKL PRM, Volume 7, Flush Types: Tex invalidate: Requires stall
bit
([20] of DW) set for all GPGPU Workloads. I added logic considering the current
renderer (brw->last_pipeline == BRW_COMPUTE_PIPELINE) and using additionally
the CS stall bit for compute (for the L3 and render cache flush).

4) But all this simply gave me the hang again in
brw_render_cache_set_check_flush() but now in 3D pipeline.

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