[PATCH i-g-t v4] tests/pm_rpm: Fix CRASH on machines that lack LLC

[David Weinehall <david.weinehall@linux.intel.com>]

On machines that lack an LLC the pm-caching subtest will
terminate with sigbus and thus CRASH during the
I915_CACHING_CACHED iteration. To work around this we reset
the caching to I915_CACHING_NONE before doing memory access.

v2: Various improvements based on feedback from Chris Wilson

v3: Fix incorrect Signed-off-by: line

v4: Further improvements based on feedback from Chris Wilson

Signed-off-by: David Weinehall <david.weinehall@linux.intel.com>
---
 tests/pm_rpm.c | 37 +++++++++++++++----------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/tests/pm_rpm.c b/tests/pm_rpm.c
index 2aa6c1018aa2..c57bf11d4e4e 100644
--- a/tests/pm_rpm.c
+++ b/tests/pm_rpm.c
@@ -1800,7 +1800,8 @@ static void pm_test_caching(void)
 	uint32_t handle;
 	uint8_t *gem_buf;
 
-	uint32_t i, got_caching;
+	uint32_t i;
+	uint32_t default_cache_level;
 	uint32_t gtt_obj_max_size = (16 * 1024);
 	uint32_t cache_levels[3] = {
 		I915_CACHING_NONE,
@@ -1808,42 +1809,34 @@ static void pm_test_caching(void)
 		I915_CACHING_DISPLAY,           /* eDRAM caching */
 	};
 
+	disable_all_screens(&ms_data);
 
 	handle = gem_create(drm_fd, gtt_obj_max_size);
+	default_cache_level = gem_get_caching(drm_fd, handle);
 	gem_buf = gem_mmap__gtt(drm_fd, handle, gtt_obj_max_size, PROT_WRITE);
 
 	for (i = 0; i < ARRAY_SIZE(cache_levels); i++) {
-		memset(gem_buf, 16 << i, gtt_obj_max_size);
+		igt_assert(wait_for_suspended());
+		gem_set_caching(drm_fd, handle, default_cache_level);
 
-		disable_all_screens_and_wait(&ms_data);
+		/* Ensure we bind the vma into the GGTT */
+		memset(gem_buf, 16 << i, gtt_obj_max_size);
 
+		/* Now try changing the cache-level on the bound object.
+		 * This will either unlikely unbind the object from the GGTT,
+		 * or more likely just change the PTEs inside the GGTT. Either
+		 * way the driver must take the rpm wakelock around the GSM
+		 * access.
+		 */
 		igt_debug("Setting cache level %u\n", cache_levels[i]);
-
+		igt_assert(wait_for_suspended());
 		gem_set_caching(drm_fd, handle, cache_levels[i]);
-
-		got_caching = gem_get_caching(drm_fd, handle);
-
-		igt_debug("Got back %u\n", got_caching);
-
-		/*
-		 * Allow fall-back to CACHING_NONE in case the platform does
-		 * not support it.
-		 */
-		if (cache_levels[i] == I915_CACHING_DISPLAY)
-			igt_assert(got_caching == I915_CACHING_NONE ||
-				   got_caching == I915_CACHING_DISPLAY);
-		else
-			igt_assert(got_caching == cache_levels[i]);
-
-		enable_one_screen_and_wait(&ms_data);
 	}
 
 	igt_assert(munmap(gem_buf, gtt_obj_max_size) == 0);
 	gem_close(drm_fd, handle);
 }
 
-
-
 static void fences_subtest(bool dpms)
 {
 	int i;
-- 
2.7.0

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