drm/i915/selftests: Update live.evict to wait on requests / idle GPU after each loop

Update live.evict to wait on last request and idle GPU after each loop.
This not only enhances the test to fill the GGTT on each engine class
but also avoid timeouts from igt_flush_test when using GuC submission.
igt_flush_test (idle GPU) can take a long time with GuC submission if
losts of contexts are created due to H2G / G2H required to destroy
contexts.
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211021214040.33292-1-matthew.brost@intel.com

drivers/gpu/drm/i915/selftests/i915_gem_evict.c

@@ -442,6 +442,7 @@ static int igt_evict_contexts(void *arg)
 	/* Overfill the GGTT with context objects and so try to evict one. */
 	for_each_engine(engine, gt, id) {
 		struct i915_sw_fence fence;
+		struct i915_request *last = NULL;
 
 		count = 0;
 		onstack_fence_init(&fence);
@@ -479,6 +480,9 @@ static int igt_evict_contexts(void *arg)
 
 			i915_request_add(rq);
 			count++;
+			if (last)
+				i915_request_put(last);
+			last = i915_request_get(rq);
 			err = 0;
 		} while(1);
 		onstack_fence_fini(&fence);
@@ -486,6 +490,21 @@ static int igt_evict_contexts(void *arg)
 			count, engine->name);
 		if (err)
 			break;
+		if (last) {
+			if (i915_request_wait(last, 0, HZ) < 0) {
+				err = -EIO;
+				i915_request_put(last);
+				pr_err("Failed waiting for last request (on %s)",
+				       engine->name);
+				break;
+			}
+			i915_request_put(last);
+		}
+		err = intel_gt_wait_for_idle(engine->gt, HZ * 3);
+		if (err) {
+			pr_err("Failed to idle GT (on %s)", engine->name);
+			break;
+		}
 	}
 
 	mutex_lock(&ggtt->vm.mutex);