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Subject[PATCH v2 4/4] Documentation: extcon: usb-gpio: update usb-gpio binding description
Add information about VBUS pin detection support, 'debounce' property
and some other details.

Signed-off-by: Robert Baldyga <>
.../devicetree/bindings/extcon/extcon-usb-gpio.txt | 28 ++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
index af0b903..7096f39 100644
--- a/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
+++ b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
@@ -1,16 +1,40 @@
USB GPIO Extcon device

-This is a virtual device used to generate USB cable states from the USB ID pin
-connected to a GPIO pin.
+This is a virtual device used to generate USB cable states from the USB
+ID and VBUS signals connected to GPIO pins.
+The extcon cable states USB and USB_HOST are actually VBUS and !ID
+pin states and do not indicate what mode the USB needs to operate in.
+That decision is done by the USB stack.
+Some devices have only one of these GPIO pins, so we support cases when
+only one of them is present. Hence properties 'id-gpio' and 'vbus-gpio'
+are described as optional, but at least one of them has to be present
+in extcon-usb-gpio node.
+In general we have three cases:
+1. If VBUS and ID gpios are present we pass them as is
+2. If only VBUS gpio is present we assume that ID pin is always High.
+ USB-HOST = false, USB = VBUS.
+3. If only ID pin is available we infer the VBUS pin states based on ID.

Required properties:
- compatible: Should be "linux,extcon-usb-gpio"
+Optional properties
- id-gpio: gpio for USB ID pin. See gpio binding.
+- vbus-gpio: gpio for USB VBUS pin. See gpio binding.
+- debounce: gpio debounce time in milliseconds (u32).

Example: Examples of extcon-usb-gpio node in dra7-evm.dts as listed below:
extcon_usb1 {
compatible = "linux,extcon-usb-gpio";
id-gpio = <&gpio6 1 GPIO_ACTIVE_HIGH>;
+ vbus-gpio = <&gpio6 2 GPIO_ACTIVE_HIGH>;
+ debounce = <25>;

&omap_dwc3_1 {

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