gpio: sx150x: correct and refine reset-on-probe behavior
Gregory Bean [Thu, 9 Sep 2010 23:38:02 +0000 (16:38 -0700)]
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>

drivers/gpio/sx150x.c
include/linux/i2c/sx150x.h

index b42f42c..823559a 100644 (file)
@@ -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);
index ee3049c..52baa79 100644 (file)
@@ -63,6 +63,9 @@
  *            IRQ lines will appear.  Similarly to gpio_base, the expander
  *            will create a block of irqs beginning at this number.
  *            This value is ignored if irq_summary is < 0.
+ * @reset_during_probe: If set to true, the driver will trigger a full
+ *                      reset of the chip at the beginning of the probe
+ *                      in order to place it in a known state.
  */
 struct sx150x_platform_data {
        unsigned gpio_base;
@@ -73,6 +76,7 @@ struct sx150x_platform_data {
        u16      io_polarity;
        int      irq_summary;
        unsigned irq_base;
+       bool     reset_during_probe;
 };
 
 #endif /* __LINUX_I2C_SX150X_H */