lib: Provide a library function to test nop execution

Sometimes a test wants to verify that an engine, or all of them, are
functional by executing a nop batch. Provide a common routine to submit
an empty batch then test whether the driver is wedged.
Reported-by: Antonio Argenziano <antonio.argenziano@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Antonio Argenziano <antonio.argenziano@intel.com>
Reviewed-by: Antonio Argenziano <antonio.argenziano@intel.com>

lib/i915/gem_submission.c

@@ -21,14 +21,18 @@
  * IN THE SOFTWARE.
  */
 
+#include <errno.h>
 #include <stdbool.h>
 #include <sys/ioctl.h>
 
 #include <i915_drm.h>
 
 #include "igt_core.h"
+#include "igt_gt.h"
 #include "igt_sysfs.h"
 #include "intel_chipset.h"
+#include "intel_reg.h"
+#include "ioctl_wrappers.h"
 
 #include "i915/gem_submission.h"
 
@@ -159,3 +163,48 @@ bool gem_has_guc_submission(int fd)
 {
 	return gem_submission_method(fd) & GEM_SUBMISSION_GUC;
 }
+
+static bool is_wedged(int i915)
+{
+	int err = 0;
+	if (ioctl(i915, DRM_IOCTL_I915_GEM_THROTTLE))
+		err = -errno;
+	return err == -EIO;
+}
+
+/**
+ * gem_test_engine:
+ * @i915: open i915 drm file descriptor
+ * @engine: the engine (I915_EXEC_RING id) to exercise
+ *
+ * Execute a nop batch on the specified, or -1 for all, and check it
+ * executes.
+ */
+void gem_test_engine(int i915, unsigned int engine)
+{
+	const uint32_t bbe = MI_BATCH_BUFFER_END;
+	struct drm_i915_gem_exec_object2 obj = {
+		.handle = gem_create(i915, 4096)
+	};
+	struct drm_i915_gem_execbuffer2 execbuf = {
+		.buffers_ptr = to_user_pointer(&obj),
+		.buffer_count = 1,
+	};
+
+	igt_assert(!is_wedged(i915));
+	gem_write(i915, obj.handle, 0, &bbe, sizeof(bbe));
+
+	if (engine == -1u) {
+		for_each_engine(i915, engine) {
+			execbuf.flags = engine;
+			gem_execbuf(i915, &execbuf);
+		}
+	} else {
+		execbuf.flags = engine;
+		gem_execbuf(i915, &execbuf);
+	}
+	gem_sync(i915, obj.handle);
+	gem_close(i915, obj.handle);
+
+	igt_assert(!is_wedged(i915));
+}

lib/i915/gem_submission.h

@@ -33,4 +33,6 @@ bool gem_has_semaphores(int fd);
 bool gem_has_execlists(int fd);
 bool gem_has_guc_submission(int fd);
 
+void gem_test_engine(int fd, unsigned int engine);
+
 #endif /* GEM_SUBMISSION_H */

tests/gem_eio.c

@@ -66,7 +66,7 @@ static void trigger_reset(int fd)
 
 	/* And just check the gpu is indeed running again */
 	igt_debug("Checking that the GPU recovered\n");
-	gem_quiescent_gpu(fd);
+	gem_test_engine(fd, -1);
 }
 
 static void wedge_gpu(int fd)

tests/pm_rpm.c

@@ -1277,7 +1277,7 @@ static void gem_idle_subtest(void)
 
 	sleep(5);
 
-	gem_quiescent_gpu(drm_fd);
+	gem_test_engine(drm_fd, -1);
 }
 
 static void gem_evict_pwrite_subtest(void)