Chris Wilson e67d01d849 drm/i915/gt: Flush xcs before tgl breadcrumbs ...

In a simple test case that writes to scratch and then busy-waits for the
batch to be signaled, we observe that the signal is before the write is
posted. That is bad news.

Splitting the flush + write_dword into two separate flush_dw prevents
the issue from being reproduced, we can presume the post-sync op is not
so post-sync.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/216
Testcase: igt/gem_exec_fence/parallel
Testcase: igt/i915_selftest/live/gt_timelines
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201102221057.29626-2-chris@chris-wilson.co.uk
(cherry picked from commit 09212e81e5)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

2020-11-03 19:22:42 -05:00

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