Messages in this thread Patch in this message | | | From | Mark Brown <> | Subject | [PATCH] regmap: Suppress noop writes in regmap_update_bits() | Date | Fri, 18 Nov 2011 16:07:56 +0000 |
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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> --- 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 e533368..10ecbba3 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); -- 1.7.7.3
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