Bluetooth: btbcm: Obtain and handle reset GPIO

Obtain and drive the optional reset GPIO line if this is
not hardwired in the platform. This is needed on the
Samsung GT-I9070 mobile phone.

The invers of power is used, this should be OK to apply
simultaneously as the power signal according to
figures 47-51 on pages 159-161 in the BCM4330 datasheet.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_bcm.c

@@ -68,6 +68,8 @@ struct bcm_device_data {
  *	deassert = Bluetooth device may sleep when sleep criteria are met
  * @shutdown: BT_REG_ON pin,
  *	power up or power down Bluetooth device internal regulators
+ * @reset: BT_RST_N pin,
+ *	active low resets the Bluetooth logic core
  * @set_device_wakeup: callback to toggle BT_WAKE pin
  *	either by accessing @device_wakeup or by calling @btlp
  * @set_shutdown: callback to toggle BT_REG_ON pin
@@ -101,6 +103,7 @@ struct bcm_device {
 	const char		*name;
 	struct gpio_desc	*device_wakeup;
 	struct gpio_desc	*shutdown;
+	struct gpio_desc	*reset;
 	int			(*set_device_wakeup)(struct bcm_device *, bool);
 	int			(*set_shutdown)(struct bcm_device *, bool);
 #ifdef CONFIG_ACPI
@@ -985,6 +988,15 @@ static int bcm_gpio_set_device_wakeup(struct bcm_device *dev, bool awake)
 static int bcm_gpio_set_shutdown(struct bcm_device *dev, bool powered)
 {
 	gpiod_set_value_cansleep(dev->shutdown, powered);
+	if (dev->reset)
+		/*
+		 * The reset line is asserted on powerdown and deasserted
+		 * on poweron so the inverse of powered is used. Notice
+		 * that the GPIO line BT_RST_N needs to be specified as
+		 * active low in the device tree or similar system
+		 * description.
+		 */
+		gpiod_set_value_cansleep(dev->reset, !powered);
 	return 0;
 }
 
@@ -1050,6 +1062,11 @@ static int bcm_get_resources(struct bcm_device *dev)
 	if (IS_ERR(dev->shutdown))
 		return PTR_ERR(dev->shutdown);
 
+	dev->reset = devm_gpiod_get_optional(dev->dev, "reset",
+					     GPIOD_OUT_LOW);
+	if (IS_ERR(dev->reset))
+		return PTR_ERR(dev->reset);
+
 	dev->set_device_wakeup = bcm_gpio_set_device_wakeup;
 	dev->set_shutdown = bcm_gpio_set_shutdown;