The patch below does not apply to the 5.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e67d01d8494640018b08cd767aeb2824a8e11983 Mon Sep 17 00:00:00 2001
From: Chris Wilson chris@chris-wilson.co.uk Date: Mon, 2 Nov 2020 22:10:57 +0000 Subject: [PATCH] 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@c... (cherry picked from commit 09212e81e5450743e5b06b27c4e344e4c45b630d) Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index d12861cf0753..f82c6dd1de18 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -4994,7 +4994,9 @@ gen12_emit_fini_breadcrumb_tail(struct i915_request *request, u32 *cs)
static u32 *gen12_emit_fini_breadcrumb(struct i915_request *rq, u32 *cs) { - return gen12_emit_fini_breadcrumb_tail(rq, emit_xcs_breadcrumb(rq, cs)); + /* XXX Stalling flush before seqno write; post-sync not */ + cs = emit_xcs_breadcrumb(rq, __gen8_emit_flush_dw(cs, 0, 0, 0)); + return gen12_emit_fini_breadcrumb_tail(rq, cs); }
static u32 *