drm/i915: Simplify error escape from cmdparser

We need to flush the destination buffer, even on error, to maintain
consistent cache state. Thereby removing the jump on error past the
clear, and reducing the loop-escape mechanism to a mere break.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191211110437.4082687-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -1453,7 +1453,7 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		if (!desc) {
 			DRM_DEBUG("CMD: Unrecognized command: 0x%08X\n", *cmd);
 			ret = -EINVAL;
-			goto err;
+			break;
 		}
 
 		if (desc->flags & CMD_DESC_FIXED)
@@ -1467,21 +1467,18 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 				  length,
 				  batch_end - cmd);
 			ret = -EINVAL;
-			goto err;
+			break;
 		}
 
 		if (!check_cmd(engine, desc, cmd, length)) {
 			ret = -EACCES;
-			goto err;
+			break;
 		}
 
 		if (desc->cmd.value == MI_BATCH_BUFFER_START) {
 			ret = check_bbstart(cmd, offset, length, batch_length,
 					    batch_addr, shadow_addr,
 					    jump_whitelist);
-
-			if (ret)
-				goto err;
 			break;
 		}
 
@@ -1493,7 +1490,7 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		if  (cmd >= batch_end) {
 			DRM_DEBUG("CMD: Got to the end of the buffer w/o a BBE cmd!\n");
 			ret = -EINVAL;
-			goto err;
+			break;
 		}
 	} while (1);
 
@@ -1503,7 +1500,6 @@ int intel_engine_cmd_parser(struct intel_engine_cs *engine,
 		drm_clflush_virt_range(ptr, (void *)(cmd + 1) - ptr);
 	}
 
-err:
 	if (!IS_ERR_OR_NULL(jump_whitelist))
 		kfree(jump_whitelist);
 	i915_gem_object_unpin_map(shadow->obj);