[PATCH AUTOSEL 5.10 1/9] regmap: Account for register length when chunking

[Sasha Levin <sashal@kernel.org>]

From: Jim Wylder <jwylder@google.com>

[ Upstream commit 3981514180c987a79ea98f0ae06a7cbf58a9ac0f ]

Currently, when regmap_raw_write() splits the data, it uses the
max_raw_write value defined for the bus.  For any bus that includes
the target register address in the max_raw_write value, the chunked
transmission will always exceed the maximum transmission length.
To avoid this problem, subtract the length of the register and the
padding from the maximum transmission.

Signed-off-by: Jim Wylder <jwylder@google.com
Link: https://lore.kernel.org/r/20230517152444.3690870-2-jwylder@google.com
Signed-off-by: Mark Brown <broonie@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/base/regmap/regmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 55a30afc14a00..2a3c3dfefdcec 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1998,6 +1998,8 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	size_t val_count = val_len / val_bytes;
 	size_t chunk_count, chunk_bytes;
 	size_t chunk_regs = val_count;
+	size_t max_data = map->max_raw_write - map->format.reg_bytes -
+			map->format.pad_bytes;
 	int ret, i;
 
 	if (!val_count)
@@ -2005,8 +2007,8 @@ int _regmap_raw_write(struct regmap *map, unsigned int reg,
 
 	if (map->use_single_write)
 		chunk_regs = 1;
-	else if (map->max_raw_write && val_len > map->max_raw_write)
-		chunk_regs = map->max_raw_write / val_bytes;
+	else if (map->max_raw_write && val_len > max_data)
+		chunk_regs = max_data / val_bytes;
 
 	chunk_count = val_count / chunk_regs;
 	chunk_bytes = chunk_regs * val_bytes;
-- 
2.39.2