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>
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index e533368e..10ecbba 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -583,18 +583,19 @@
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);