regmap: Lock the sync path, ensure we use the lockless _regmap_write()

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
index 2caf6e4..59e432c 100644
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -230,6 +230,7 @@
 
 	BUG_ON(!map->cache_ops);
 
+	mutex_lock(&map->lock);
 	dev_dbg(map->dev, "Syncing %s cache\n",
 		map->cache_ops->name);
 	name = map->cache_ops->name;
@@ -242,7 +243,7 @@
 			if (ret < 0)
 				goto out;
 			map->cache_bypass = 1;
-			ret = regmap_write(map, i, val);
+			ret = _regmap_write(map, i, val);
 			map->cache_bypass = 0;
 			if (ret < 0)
 				goto out;
@@ -254,6 +255,7 @@
 	}
 out:
 	trace_regcache_sync(map->dev, name, "stop");
+	mutex_unlock(&map->lock);
 
 	return ret;
 }