regmap: Account for register length when chunking

commit 3981514180c987a79ea98f0ae06a7cbf58a9ac0f upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 7de1f27..8359164 100644 (file)
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2064,6 +2064,8 @@ 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)
@@ -2071,8 +2073,8 @@ 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;