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| author |   Mark Brown <broonie@opensource.wolfsonmicro.com> | 2011-11-18 16:03:50 +0000 |
|---|---|---|
| committer | Mark Brown <broonie@opensource.wolfsonmicro.com> | 2011-11-20 20:56:38 +0000 |
| commit | d91e8db2c3bbe8ef0e2f3e1a6ff5b31a8d53ef16 (patch) | |
| tree | 2bcc299fa62738407b5e25483230f7249f0d016d /drivers/base/regmap | |
| parent | regmap: Remove indexed cache type (diff) | |
| download | linux-dev-d91e8db2c3bbe8ef0e2f3e1a6ff5b31a8d53ef16.tar.xz linux-dev-d91e8db2c3bbe8ef0e2f3e1a6ff5b31a8d53ef16.zip | |
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/regmap')
| -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, unsigned int mask, unsigned int val) { int ret; - unsigned int tmp; + unsigned int tmp, orig; mutex_lock(&map->lock); - ret = _regmap_read(map, reg, &tmp); + ret = _regmap_read(map, reg, &orig); if (ret != 0) goto out; - tmp &= ~mask; + tmp = orig & ~mask; tmp |= val & mask; - ret = _regmap_write(map, reg, tmp); + if (tmp != orig) + ret = _regmap_write(map, reg, tmp); out: mutex_unlock(&map->lock); |