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);