regmap: Implement generic syncing functionality

In the absence of a sync callback, do it manually.  This of course
can't take advantange of the specific optimizations of each
cache type but it will do well enough in most cases.
Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache.c

@@ -223,20 +223,39 @@ EXPORT_SYMBOL_GPL(regcache_write);
  */
 int regcache_sync(struct regmap *map)
 {
-	int ret;
+	int ret = 0;
+	unsigned int val;
+	unsigned int i;
 	const char *name;
 
 	BUG_ON(!map->cache_ops);
 
-	if (map->cache_ops->sync) {
 	dev_dbg(map->dev, "Syncing %s cache\n",
 		map->cache_ops->name);
 	name = map->cache_ops->name;
 	trace_regcache_sync(map->dev, name, "start");
+	if (map->cache_ops->sync) {
 		ret = map->cache_ops->sync(map);
-		trace_regcache_sync(map->dev, name, "stop");
+	} else {
+		for (i = 0; i < map->num_reg_defaults; i++) {
+			ret = regcache_read(map, i, &val);
+			if (ret < 0)
+				goto out;
+			regcache_cache_bypass(map, true);
+			ret = regcache_write(map, i, val);
+			regcache_cache_bypass(map, false);
+			if (ret < 0)
+				goto out;
+			dev_dbg(map->dev, "Synced register %#x, value %#x\n",
+				map->reg_defaults[i].reg,
+				map->reg_defaults[i].def);
 		}
-	return 0;
+
+	}
+out:
+	trace_regcache_sync(map->dev, name, "stop");
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(regcache_sync);