From 2728200f48d315748b4fb2b2525e1ac211e97ecf Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Wed, 16 Oct 2019 23:57:30 +0100
Subject: drm/i915/selftests: Force ordering of context switches
Git-commit: 2728200f48d315748b4fb2b2525e1ac211e97ecf
Patch-mainline: v5.5-rc1
References: bsc#1152489

The parallel switch test has an underlying assumption that its requests
are executed in order of submission, which is only true if the backend
manages to keep up. Ensure the order of execution matches the submission
order by explicit dependencies and so when we wait on the last request,
we know we wait on completion of the entire queue.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191016225730.29447-1-chris@chris-wilson.co.uk
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 .../drm/i915/gem/selftests/i915_gem_context.c | 35 +++++++++++++++----
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
index 8f72f173db03..2c65c9e95cc5 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
@@ -169,18 +169,24 @@ static int __live_parallel_switch1(void *data)
 		struct i915_request *rq = NULL;
 		int err, n;
 
-		for (n = 0; n < ARRAY_SIZE(arg->ce); n++) {
-			i915_request_put(rq);
+		err = 0;
+		for (n = 0; !err && n < ARRAY_SIZE(arg->ce); n++) {
+			struct i915_request *prev = rq;
 
 			rq = i915_request_create(arg->ce[n]);
-			if (IS_ERR(rq))
+			if (IS_ERR(rq)) {
+				i915_request_put(prev);
 				return PTR_ERR(rq);
+			}
 
 			i915_request_get(rq);
+			if (prev) {
+				err = i915_request_await_dma_fence(rq, &prev->fence);
+				i915_request_put(prev);
+			}
+
 			i915_request_add(rq);
 		}
-
-		err = 0;
 		if (i915_request_wait(rq, 0, HZ / 5) < 0)
 			err = -ETIME;
 		i915_request_put(rq);
@@ -197,6 +203,7 @@ static int __live_parallel_switch1(void *data)
 static int __live_parallel_switchN(void *data)
 {
 	struct parallel_switch *arg = data;
+	struct i915_request *rq = NULL;
 	IGT_TIMEOUT(end_time);
 	unsigned long count;
 	int n;
@@ -204,17 +211,31 @@ static int __live_parallel_switchN(void *data)
 	count = 0;
 	do {
 		for (n = 0; n < ARRAY_SIZE(arg->ce); n++) {
-			struct i915_request *rq;
+			struct i915_request *prev = rq;
+			int err = 0;
 
 			rq = i915_request_create(arg->ce[n]);
-			if (IS_ERR(rq))
+			if (IS_ERR(rq)) {
+				i915_request_put(prev);
 				return PTR_ERR(rq);
+			}
+
+			i915_request_get(rq);
+			if (prev) {
+				err = i915_request_await_dma_fence(rq, &prev->fence);
+				i915_request_put(prev);
+			}
 
 			i915_request_add(rq);
+			if (err) {
+				i915_request_put(rq);
+				return err;
+			}
 		}
 
 		count++;
 	} while (!__igt_timeout(end_time, NULL));
+	i915_request_put(rq);
 
 	pr_info("%s: %lu switches (many)\n", arg->ce[0]->engine->name, count);
 	return 0;
-- 
2.28.0