[RFC 6/9] regmap: Speed up _regmap_raw_write_impl() for large buffers

[Noralf Trønnes]

When writing a 3MB buffer the unwritable check in _regmap_raw_write_impl()
adds a ~20ms overhead on a Raspberry Pi 4.
Amend this by avoiding the check if it's not necessary.

Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
---
 drivers/base/regmap/regmap.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 19f57ccfbe1d..cd876309a74b 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1489,10 +1489,12 @@ 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;
+	if (map->max_register || map->writeable_reg || map->wr_table) {
+		for (i = 0; i < val_len / map->format.val_bytes; i++)
+			if (!regmap_writeable(map,
+					      reg + regmap_get_offset(map, i)))
+				return -EINVAL;
+	}
 
 	if (!map->cache_bypass && map->format.parse_val) {
 		unsigned int ival;
-- 
2.23.0