drm/i915: Include engine->last_submitted_seqno in GPU error state

It's useful to look at the last seqno submitted on a particular engine
and compare it against the HWS value to check for irregularities.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460010558-10705-1-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1363,8 +1363,10 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused)
 
 	for_each_engine_id(engine, dev_priv, id) {
 		seq_printf(m, "%s:\n", engine->name);
-		seq_printf(m, "\tseqno = %x [current %x]\n",
-			   engine->hangcheck.seqno, seqno[id]);
+		seq_printf(m, "\tseqno = %x [current %x, last %x]\n",
+			   engine->hangcheck.seqno,
+			   seqno[id],
+			   engine->last_submitted_seqno);
 		seq_printf(m, "\tACTHD = 0x%08llx [current 0x%08llx]\n",
 			   (long long)engine->hangcheck.acthd,
 			   (long long)acthd[id]);

drivers/gpu/drm/i915/i915_drv.h

@@ -495,6 +495,7 @@ struct drm_i915_error_state {
 		u32 cpu_ring_head;
 		u32 cpu_ring_tail;
 
+		u32 last_seqno;
 		u32 semaphore_seqno[I915_NUM_ENGINES - 1];
 
 		/* Register state */

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -296,6 +296,7 @@ static void i915_ring_error_state(struct drm_i915_error_state_buf *m,
 		}
 	}
 	err_printf(m, "  seqno: 0x%08x\n", ring->seqno);
+	err_printf(m, "  last_seqno: 0x%08x\n", ring->last_seqno);
 	err_printf(m, "  waiting: %s\n", yesno(ring->waiting));
 	err_printf(m, "  ring->head: 0x%08x\n", ring->cpu_ring_head);
 	err_printf(m, "  ring->tail: 0x%08x\n", ring->cpu_ring_tail);
@@ -932,6 +933,7 @@ static void i915_record_ring_state(struct drm_device *dev,
 	ering->instpm = I915_READ(RING_INSTPM(engine->mmio_base));
 	ering->seqno = engine->get_seqno(engine, false);
 	ering->acthd = intel_ring_get_active_head(engine);
+	ering->last_seqno = engine->last_submitted_seqno;
 	ering->start = I915_READ_START(engine);
 	ering->head = I915_READ_HEAD(engine);
 	ering->tail = I915_READ_TAIL(engine);