drm/i915: Use hangcheck score to find guilty context

With full ppgtt using acthd is not enough to find guilty
batch buffer. We get multiple false positives as acthd is
per vm.

Instead of scanning which vm was running on a ring,
to find corressponding context, use a different, simpler,
strategy of finding batches that caused gpu hang:

If hangcheck has declared ring to be hung, find first non complete
request on that ring and claim it was guilty.

v2: Rebase

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73652
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b226ae6..ec9eec4 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2532,7 +2532,6 @@
 #define BUSY 1
 #define KICK 5
 #define HUNG 20
-#define FIRE 30
 
 	if (!i915.enable_hangcheck)
 		return;
@@ -2616,7 +2615,7 @@
 	}
 
 	for_each_ring(ring, dev_priv, i) {
-		if (ring->hangcheck.score > FIRE) {
+		if (ring->hangcheck.score >= HANGCHECK_SCORE_RING_HUNG) {
 			DRM_INFO("%s on %s\n",
 				 stuck[i] ? "stuck" : "no progress",
 				 ring->name);