CHROMIUM: mfd: max77686: don't read when updating if mask is 0xff

If an update is going to set all of the bits of a register, there is no
reason to read its value first.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
BUG=chrome-os-partner:10891
TEST=builds clean and snow boots;
TEST=ftrace shows that most update_reg calls, when mask is 0xff, only
     cause a single i2c write

Change-Id: I14270ba5f3ef6d060401a7c6c69b6f493a9f6588
Reviewed-on: https://gerrit.chromium.org/gerrit/30551
Reviewed-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Commit-Ready: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>

diff --git a/drivers/mfd/max77686.c b/drivers/mfd/max77686.c
index 3a3c75f..e78e2f9 100644 (file)
--- a/drivers/mfd/max77686.c
+++ b/drivers/mfd/max77686.c
@@ -110,6 +110,9 @@ int max77686_update_reg(struct i2c_client *i2c, u8 reg, u8 val, u8 mask)
        struct max77686_dev *max77686 = i2c_get_clientdata(i2c);
        int ret;
 
+       if (mask == 0xff)
+               return max77686_write_reg(i2c, reg, val);
+
        mutex_lock(&max77686->iolock);
        ret = i2c_smbus_read_byte_data(i2c, reg);
        if (ret >= 0) {