regmap: Use async I/O during cache sync

Try to speed up I/O a little by not synchronising until we are finished
scheduling writes. A brief survey of existing users suggests we have none
that would currently benefit from an async cache sync.
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/base/regmap/regcache.c

@@ -307,6 +307,8 @@ int regcache_sync(struct regmap *map)
 	if (!map->cache_dirty)
 		goto out;
 
+	map->async = true;
+
 	/* Apply any patch first */
 	map->cache_bypass = 1;
 	for (i = 0; i < map->patch_regs; i++) {
@@ -332,11 +334,15 @@ int regcache_sync(struct regmap *map)
 		map->cache_dirty = false;
 
 out:
-	trace_regcache_sync(map->dev, name, "stop");
 	/* Restore the bypass state */
+	map->async = false;
 	map->cache_bypass = bypass;
 	map->unlock(map->lock_arg);
 
+	regmap_async_complete(map);
+
+	trace_regcache_sync(map->dev, name, "stop");
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regcache_sync);
@@ -375,17 +381,23 @@ int regcache_sync_region(struct regmap *map, unsigned int min,
 	if (!map->cache_dirty)
 		goto out;
 
+	map->async = true;
+
 	if (map->cache_ops->sync)
 		ret = map->cache_ops->sync(map, min, max);
 	else
 		ret = regcache_default_sync(map, min, max);
 
 out:
-	trace_regcache_sync(map->dev, name, "stop region");
 	/* Restore the bypass state */
 	map->cache_bypass = bypass;
+	map->async = false;
 	map->unlock(map->lock_arg);
 
+	regmap_async_complete(map);
+
+	trace_regcache_sync(map->dev, name, "stop region");
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regcache_sync_region);