mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-26 21:13:48 +00:00
72 lines
2.9 KiB
Text
72 lines
2.9 KiB
Text
|
* PCF857x-compatible I/O expanders
|
||
|
|
|
||
|
|
The PCF857x-compatible chips have "quasi-bidirectional" I/O lines that can be
|
||
|
|
driven high by a pull-up current source or driven low to ground. This combines
|
||
|
|
the direction and output level into a single bit per line, which can't be read
|
||
|
|
back. We can't actually know at initialization time whether a line is configured
|
||
|
|
(a) as output and driving the signal low/high, or (b) as input and reporting a
|
||
|
|
low/high value, without knowing the last value written since the chip came out
|
||
|
|
of reset (if any). The only reliable solution for setting up line direction is
|
||
|
|
thus to do it explicitly.
|
||
|
|
|
||
|
|
Required Properties:
|
||
|
|
|
||
|
|
- compatible: should be one of the following.
|
||
|
|
- "maxim,max7328": For the Maxim MAX7378
|
||
|
|
- "maxim,max7329": For the Maxim MAX7329
|
||
|
|
- "nxp,pca8574": For the NXP PCA8574
|
||
|
|
- "nxp,pca8575": For the NXP PCA8575
|
||
|
|
- "nxp,pca9670": For the NXP PCA9670
|
||
|
|
- "nxp,pca9671": For the NXP PCA9671
|
||
|
|
- "nxp,pca9672": For the NXP PCA9672
|
||
|
|
- "nxp,pca9673": For the NXP PCA9673
|
||
|
|
- "nxp,pca9674": For the NXP PCA9674
|
||
|
|
- "nxp,pca9675": For the NXP PCA9675
|
||
|
|
- "nxp,pcf8574": For the NXP PCF8574
|
||
|
|
- "nxp,pcf8574a": For the NXP PCF8574A
|
||
|
|
- "nxp,pcf8575": For the NXP PCF8575
|
||
|
|
- "ti,tca9554": For the TI TCA9554
|
||
|
|
|
||
|
|
- reg: I2C slave address.
|
||
|
|
|
||
|
|
- gpio-controller: Marks the device node as a gpio controller.
|
||
|
|
- #gpio-cells: Should be 2. The first cell is the GPIO number and the second
|
||
|
|
cell specifies GPIO flags, as defined in <dt-bindings/gpio/gpio.h>. Only the
|
||
|
|
GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW flags are supported.
|
||
|
|
|
||
|
|
Optional Properties:
|
||
|
|
|
||
|
|
- lines-initial-states: Bitmask that specifies the initial state of each
|
||
|
|
line. When a bit is set to zero, the corresponding line will be initialized to
|
||
|
|
the input (pulled-up) state. When the bit is set to one, the line will be
|
||
|
|
initialized the low-level output state. If the property is not specified
|
||
|
|
all lines will be initialized to the input state.
|
||
|
|
|
||
|
|
The I/O expander can detect input state changes, and thus optionally act as
|
||
|
|
an interrupt controller. When the expander interrupt line is connected all the
|
||
|
|
following properties must be set. For more information please see the
|
||
|
|
interrupt controller device tree bindings documentation available at
|
||
|
|
Documentation/devicetree/bindings/interrupt-controller/interrupts.txt.
|
||
|
|
|
||
|
|
- interrupt-controller: Identifies the node as an interrupt controller.
|
||
|
|
- #interrupt-cells: Number of cells to encode an interrupt source, shall be 2.
|
||
|
|
- interrupt-parent: phandle of the parent interrupt controller.
|
||
|
|
- interrupts: Interrupt specifier for the controllers interrupt.
|
||
|
|
|
||
|
|
|
||
|
|
Please refer to gpio.txt in this directory for details of the common GPIO
|
||
|
|
bindings used by client devices.
|
||
|
|
|
||
|
|
Example: PCF8575 I/O expander node
|
||
|
|
|
||
|
|
pcf8575: gpio@20 {
|
||
|
|
compatible = "nxp,pcf8575";
|
||
|
|
reg = <0x20>;
|
||
|
|
interrupt-parent = <&irqpin2>;
|
||
|
|
interrupts = <3 0>;
|
||
|
|
gpio-controller;
|
||
|
|
#gpio-cells = <2>;
|
||
|
|
interrupt-controller;
|
||
|
|
#interrupt-cells = <2>;
|
||
|
|
};
|