[PATCH v3] drm/i915/gt: Do not consider preemption during execlists_dequeue for gen8

[Nitin Gote]

We're seeing a GPU HANG issue on a CHV platform, which was caused by
bac24f59f454 ("drm/i915/execlists: Enable coarse preemption boundaries for gen8").

Gen8 platform has only timeslice and doesn't support a preemption mechanism
as engines do not have a preemption timer and doesn't send an irq if the
preemption timeout expires. So, add a fix to not consider preemption
during dequeuing for gen8 platforms.

v2: Simplify can_preempt() function (Tvrtko Ursulin)

v3:
 - Inside need_preempt(), condition of can_preempt() is not required
   as simplified can_preempt() is enough. (Chris Wilson)

Fixes: bac24f59f454 ("drm/i915/execlists: Enable coarse preemption boundaries for gen8")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11396
Suggested-by: Andi Shyti <andi.shyti at intel.com>
Signed-off-by: Nitin Gote <nitin.r.gote at intel.com>
Cc: Chris Wilson <chris.p.wilson at linux.intel.com>
CC: <stable at vger.kernel.org> # v5.2+
---
 drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index 21829439e686..72090f52fb85 100644
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -3315,11 +3315,7 @@ static void remove_from_engine(struct i915_request *rq)
 
 static bool can_preempt(struct intel_engine_cs *engine)
 {
-	if (GRAPHICS_VER(engine->i915) > 8)
-		return true;
-
-	/* GPGPU on bdw requires extra w/a; not implemented */
-	return engine->class != RENDER_CLASS;
+	return GRAPHICS_VER(engine->i915) > 8;
 }
 
 static void kick_execlists(const struct i915_request *rq, int prio)
-- 
2.25.1