regmap: fix writes to non incrementing registers

When checking if a register block is writable we must ensure that the
block does not start with or contain a non incrementing register.

Fixes: 8b9f9d4dc5 ("regmap: verify if register is writeable before writing operations")
Signed-off-by: Ben Whitten <ben.whitten@gmail.com>
Link: https://lore.kernel.org/r/20200118205625.14532-1-ben.whitten@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap.c

@@ -1488,11 +1488,18 @@ static int _regmap_raw_write_impl(struct regmap *map, unsigned int reg,
 
 	WARN_ON(!map->bus);
 
-	/* Check for unwritable registers before we start */
-	for (i = 0; i < val_len / map->format.val_bytes; i++)
-		if (!regmap_writeable(map,
-				     reg + regmap_get_offset(map, i)))
-			return -EINVAL;
+	/* Check for unwritable or noinc registers in range
+	 * before we start
+	 */
+	if (!regmap_writeable_noinc(map, reg)) {
+		for (i = 0; i < val_len / map->format.val_bytes; i++) {
+			unsigned int element =
+				reg + regmap_get_offset(map, i);
+			if (!regmap_writeable(map, element) ||
+				regmap_writeable_noinc(map, element))
+				return -EINVAL;
+		}
+	}
 
 	if (!map->cache_bypass && map->format.parse_val) {
 		unsigned int ival;