[PATCH] extcon-usb-gpio: add enable pin support

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Sometimes  there's a real  OTG chip behind the USB ID signal mapped to a GPIO
pin: in my case it's Maxim Integrated MAX3355E which  integrates Vbus charge
pump and comparators and passes  thru the ID  signal  from an OTG connector.
This chip also has the SHDN# pin which  should be  driven high for the normal
operation  and low to  save power;  it  is connected to a GPIO pin as well on,
hence  we'll have  to  teach the driver to parse the new optional device tree
property, "enable-gpio"...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>

---
The patch is against the 'extcon-next' branch of the 'extcon.git' repo.

 Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt |    3 +++
 drivers/extcon/extcon-usb-gpio.c                             |    5 +++++
 2 files changed, 8 insertions(+)

Index: extcon/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
===================================================================
--- extcon.orig/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
+++ extcon/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
@@ -7,6 +7,9 @@ Required properties:
 - compatible: Should be "linux,extcon-usb-gpio"
 - id-gpio: gpio for USB ID pin. See gpio binding.
 
+Optional properties:
+- enable-gpio: gpio for the enable pin. See gpio binding.
+
 Example: Examples of extcon-usb-gpio node in dra7-evm.dts as listed below:
 	extcon_usb1 {
 		compatible = "linux,extcon-usb-gpio";
Index: extcon/drivers/extcon/extcon-usb-gpio.c
===================================================================
--- extcon.orig/drivers/extcon/extcon-usb-gpio.c
+++ extcon/drivers/extcon/extcon-usb-gpio.c
@@ -33,6 +33,7 @@ struct usb_extcon_info {
 	struct device *dev;
 	struct extcon_dev *edev;
 
+	struct gpio_desc *enable_gpiod;
 	struct gpio_desc *id_gpiod;
 	int id_irq;
 
@@ -99,6 +100,8 @@ static int usb_extcon_probe(struct platf
 		return -ENOMEM;
 
 	info->dev = dev;
+	info->enable_gpiod = devm_gpiod_get_optional(&pdev->dev, "enable",
+						     GPIOD_OUT_HIGH);
 	info->id_gpiod = devm_gpiod_get(&pdev->dev, "id", GPIOD_IN);
 	if (IS_ERR(info->id_gpiod)) {
 		dev_err(dev, "failed to get ID GPIO\n");
@@ -155,6 +158,8 @@ static int usb_extcon_remove(struct plat
 
 	cancel_delayed_work_sync(&info->wq_detcable);
 
+	gpiod_set_value_cansleep(info->enable_gpiod, 0);
+
 	return 0;
 }