drm/i915/gt: Expand bad CS completion event debug

Show the ring/request/context state if we see what we believe is an
early CS completion.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211230944.1203098-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_context.c

@@ -116,7 +116,8 @@ int __intel_context_do_pin(struct intel_context *ce)
 		if (unlikely(err))
 			goto err_active;
 
-		CE_TRACE(ce, "pin ring:{head:%04x, tail:%04x}\n",
+		CE_TRACE(ce, "pin ring:{start:%08x, head:%04x, tail:%04x}\n",
+			 i915_ggtt_offset(ce->ring->vma),
 			 ce->ring->head, ce->ring->tail);
 
 		smp_mb__before_atomic(); /* flush pin before it is visible */

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -2328,8 +2328,35 @@ static void process_csb(struct intel_engine_cs *engine)
 			 * coherent (visible from the CPU) before the
 			 * user interrupt and CSB is processed.
 			 */
-			GEM_BUG_ON(!i915_request_completed(*execlists->active) &&
-				   !reset_in_progress(execlists));
+			if (GEM_SHOW_DEBUG() &&
+			    !i915_request_completed(*execlists->active) &&
+			    !reset_in_progress(execlists)) {
+				struct i915_request *rq = *execlists->active;
+				const u32 *regs = rq->context->lrc_reg_state;
+
+				ENGINE_TRACE(engine,
+					     "ring:{start:0x%08x, head:%04x, tail:%04x, ctl:%08x, mode:%08x}\n",
+					     ENGINE_READ(engine, RING_START),
+					     ENGINE_READ(engine, RING_HEAD) & HEAD_ADDR,
+					     ENGINE_READ(engine, RING_TAIL) & TAIL_ADDR,
+					     ENGINE_READ(engine, RING_CTL),
+					     ENGINE_READ(engine, RING_MI_MODE));
+				ENGINE_TRACE(engine,
+					     "rq:{start:%08x, head:%04x, tail:%04x, seqno:%llx:%d, hwsp:%d}, ",
+					     i915_ggtt_offset(rq->ring->vma),
+					     rq->head, rq->tail,
+					     rq->fence.context,
+					     lower_32_bits(rq->fence.seqno),
+					     hwsp_seqno(rq));
+				ENGINE_TRACE(engine,
+					     "ctx:{start:%08x, head:%04x, tail:%04x}, ",
+					     regs[CTX_RING_START],
+					     regs[CTX_RING_HEAD],
+					     regs[CTX_RING_TAIL]);
+
+				GEM_BUG_ON("context completed before request");
+			}
+
 			execlists_schedule_out(*execlists->active++);
 
 			GEM_BUG_ON(execlists->active - execlists->inflight >