Commit d91e8db2 authored by Mark Brown's avatar Mark Brown
Browse files

regmap: Suppress noop writes in regmap_update_bits() 



If the new register value is identical to the original one then suppress
the write to the hardware in regmap_update_bits(), saving some I/O cost.

Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
parent 4c691664

drivers/base/regmap/regmap.c

+5 −4
Original line number Original line Diff line number Diff line
@@ -583,17 +583,18 @@ int regmap_update_bits(struct regmap *map, unsigned int reg, 
		       unsigned int mask, unsigned int val)

		       unsigned int mask, unsigned int val)

{

{

	int ret;

	int ret;

	unsigned int tmp;

	unsigned int tmp, orig;





	mutex_lock(&map->lock);

	mutex_lock(&map->lock);





	ret = _regmap_read(map, reg, &tmp);

	ret = _regmap_read(map, reg, &orig);

	if (ret != 0)

	if (ret != 0)

		goto out;

		goto out;





	tmp &= ~mask;

	tmp = orig & ~mask;

	tmp |= val & mask;

	tmp |= val & mask;





	if (tmp != orig)

		ret = _regmap_write(map, reg, tmp);

		ret = _regmap_write(map, reg, tmp);





out:

out: