gpio: sx150x: correct and refine reset-on-probe behavior

Replace the arbitrary software-reset call from the device-probe
method, because:

- It is defective.  To work correctly, it should be two byte writes,
  not a single word write.  As it stands, it does nothing.

- Some devices with sx150x expanders installed have their NRESET pins
  ganged on the same line, so resetting one causes the others to reset -
  not a nice thing to do arbitrarily!

- The probe, usually taking place at boot, implies a recent hard-reset,
  so a software reset at this point is just a waste of energy anyway.

Therefore, make it optional, defaulting to off, as this will match the
common case of probing at powerup and also matches the current broken
no-op behavior.

Signed-off-by: Gregory Bean <gbean@codeaurora.org>
Reviewed-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/drivers/gpio/sx150x.c b/drivers/gpio/sx150x.c
index b42f42ca70c3..823559ab0e24 100644
--- a/drivers/gpio/sx150x.c
+++ b/drivers/gpio/sx150x.c
@@ -459,17 +459,33 @@ static int sx150x_init_io(struct sx150x_chip *chip, u8 base, u16 cfg)
 	return err;
 }
 
-static int sx150x_init_hw(struct sx150x_chip *chip,
-			struct sx150x_platform_data *pdata)
+static int sx150x_reset(struct sx150x_chip *chip)
 {
-	int err = 0;
+	int err;
 
-	err = i2c_smbus_write_word_data(chip->client,
+	err = i2c_smbus_write_byte_data(chip->client,
 					chip->dev_cfg->reg_reset,
-					0x3412);
+					0x12);
 	if (err < 0)
 		return err;
 
+	err = i2c_smbus_write_byte_data(chip->client,
+					chip->dev_cfg->reg_reset,
+					0x34);
+	return err;
+}
+
+static int sx150x_init_hw(struct sx150x_chip *chip,
+			struct sx150x_platform_data *pdata)
+{
+	int err = 0;
+
+	if (pdata->reset_during_probe) {
+		err = sx150x_reset(chip);
+		if (err < 0)
+			return err;
+	}
+
 	err = sx150x_i2c_write(chip->client,
 			chip->dev_cfg->reg_misc,
 			0x01);