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regmap: Suppress noop writes in regmap_update_bits()

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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>
This commit is contained in:
Mark Brown 2011-11-18 16:03:50 +00:00
parent 4c69166458
commit d91e8db2c3
1 changed files with 5 additions and 4 deletions
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9
drivers/base/regmap/regmap.c
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@ -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);