regmap: cache: Use raw I/O to sync rbtrees if we can

This will bring no meaningful benefit by itself, it is done as a separate
commit to aid bisection if there are problems with the following commits
adding support for coalescing adjacent writes.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache-rbtree.c

@@ -55,6 +55,12 @@ static unsigned int regcache_rbtree_get_register(struct regmap *map,
 	return regcache_get_val(map, rbnode->block, idx);
 }
 
+static const void *regcache_rbtree_get_reg_addr(struct regmap *map,
+	struct regcache_rbtree_node *rbnode, unsigned int idx)
+{
+	return regcache_get_val_addr(map, rbnode->block, idx);
+}
+
 static void regcache_rbtree_set_register(struct regmap *map,
 					 struct regcache_rbtree_node *rbnode,
 					 unsigned int idx, unsigned int val)
@@ -442,6 +448,7 @@ static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
 	struct regcache_rbtree_node *rbnode;
 	unsigned int regtmp;
 	unsigned int val;
+	const void *addr;
 	int ret;
 	int i, base, end;
 
@@ -480,7 +487,17 @@ static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
 				continue;
 
 			map->cache_bypass = 1;
+
+			if (regmap_can_raw_write(map)) {
+				addr = regcache_rbtree_get_reg_addr(map,
+								    rbnode, i);
+				ret = _regmap_raw_write(map, regtmp, addr,
+							map->format.val_bytes,
+							false);
+			} else {
 				ret = _regmap_write(map, regtmp, val);
+			}
+
 			map->cache_bypass = 0;
 			if (ret)
 				return ret;