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dt-bindings: gpio: add raspberry pi GPIO expander binding

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The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware over
I2C. The firmware mailbox interface allows the ARM core to control the
GPIO lines.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Baruch Siach 2018-02-20 14:19:32 +02:00 committed by Linus Walleij
parent 08af112e79
commit 9777d8099a
1 changed files with 30 additions and 0 deletions
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Documentation/devicetree/bindings/gpio/raspberrypi,firmware-gpio.txt Normal file
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Raspberry Pi GPIO expander
The Raspberry Pi 3 GPIO expander is controlled by the VC4 firmware. The
firmware exposes a mailbox interface that allows the ARM core to control the
GPIO lines on the expander.
The Raspberry Pi GPIO expander node must be a child node of the Raspberry Pi
firmware node.
Required properties:
- compatible : Should be "raspberrypi,firmware-gpio"
- gpio-controller : Marks the device node as a gpio controller
- #gpio-cells : Should be two. The first cell is the pin number, and
the second cell is used to specify the gpio polarity:
0 = active high
1 = active low
Example:
firmware: firmware-rpi {
compatible = "raspberrypi,bcm2835-firmware";
mboxes = <&mailbox>;
expgpio: gpio {
compatible = "raspberrypi,firmware-gpio";
gpio-controller;
#gpio-cells = <2>;
};
};