diff options
author | Mark Brown <broonie@opensource.wolfsonmicro.com> | 2011-11-18 11:03:50 -0500 |
---|---|---|
committer | Mark Brown <broonie@opensource.wolfsonmicro.com> | 2011-11-20 15:56:38 -0500 |
commit | d91e8db2c3bbe8ef0e2f3e1a6ff5b31a8d53ef16 (patch) | |
tree | 2bcc299fa62738407b5e25483230f7249f0d016d /drivers/base | |
parent | 4c691664583ef6a91f9ed0e08a75fbd30a5ffd5c (diff) |
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: Mark Brown <broonie@opensource.wolfsonmicro.com>
Diffstat (limited to 'drivers/base')
-rw-r--r-- | drivers/base/regmap/regmap.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index e533368e5598..10ecbba32e10 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c | |||
@@ -583,18 +583,19 @@ int regmap_update_bits(struct regmap *map, unsigned int reg, | |||
583 | unsigned int mask, unsigned int val) | 583 | unsigned int mask, unsigned int val) |
584 | { | 584 | { |
585 | int ret; | 585 | int ret; |
586 | unsigned int tmp; | 586 | unsigned int tmp, orig; |
587 | 587 | ||
588 | mutex_lock(&map->lock); | 588 | mutex_lock(&map->lock); |
589 | 589 | ||
590 | ret = _regmap_read(map, reg, &tmp); | 590 | ret = _regmap_read(map, reg, &orig); |
591 | if (ret != 0) | 591 | if (ret != 0) |
592 | goto out; | 592 | goto out; |
593 | 593 | ||
594 | tmp &= ~mask; | 594 | tmp = orig & ~mask; |
595 | tmp |= val & mask; | 595 | tmp |= val & mask; |
596 | 596 | ||
597 | ret = _regmap_write(map, reg, tmp); | 597 | if (tmp != orig) |
598 | ret = _regmap_write(map, reg, tmp); | ||
598 | 599 | ||
599 | out: | 600 | out: |
600 | mutex_unlock(&map->lock); | 601 | mutex_unlock(&map->lock); |