drm/i915/cmdparser: Use explicit goto for error paths

In the next patch we will be adding a second valid
termination condition which will require a small
amount of refactoring to share logic with the BB_END
case.

Refactor all error conditions to jump to a dedicated
exit path, with 'break' reserved only for a successful
parse.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Jon Bloomfield <jon.bloomfield@intel.com>
Reviewed-by: Chris Wilson <chris.p.wilson@intel.com>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -1338,21 +1338,15 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 	do {
 		u32 length;
 
-		if (*cmd == MI_BATCH_BUFFER_END) {
-			if (needs_clflush_after) {
-				void *ptr = page_mask_bits(shadow_batch_obj->mm.mapping);
-				drm_clflush_virt_range(ptr,
-						       (void *)(cmd + 1) - ptr);
-			}
+		if (*cmd == MI_BATCH_BUFFER_END)
 			break;
-		}
 
 		desc = find_cmd(engine, *cmd, desc, &default_desc);
 		if (!desc) {
 			DRM_DEBUG_DRIVER("CMD: Unrecognized command: 0x%08X\n",
 					 *cmd);
 			ret = -EINVAL;
-			break;
+			goto err;
 		}
 
 		/*
@@ -1362,7 +1356,7 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		 */
 		if (desc->cmd.value == MI_BATCH_BUFFER_START) {
 			ret = -EACCES;
-			break;
+			goto err;
 		}
 
 		if (desc->flags & CMD_DESC_FIXED)
@@ -1376,22 +1370,29 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 					 length,
 					 batch_end - cmd);
 			ret = -EINVAL;
-			break;
+			goto err;
 		}
 
 		if (!check_cmd(engine, desc, cmd, length)) {
 			ret = -EACCES;
-			break;
+			goto err;
 		}
 
 		cmd += length;
 		if  (cmd >= batch_end) {
 			DRM_DEBUG_DRIVER("CMD: Got to the end of the buffer w/o a BBE cmd!\n");
 			ret = -EINVAL;
-			break;
+			goto err;
 		}
 	} while (1);
 
+	if (needs_clflush_after) {
+		void *ptr = page_mask_bits(shadow_batch_obj->mm.mapping);
+
+		drm_clflush_virt_range(ptr, (void *)(cmd + 1) - ptr);
+	}
+
+err:
 	i915_gem_object_unpin_map(shadow_batch_obj);
 	return ret;
 }