diff options
Diffstat (limited to 'Documentation/devicetree/bindings')
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio.txt | 40 |
1 files changed, 26 insertions, 14 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt index 3fb8f53071b8..b9bd1d64cfa6 100644 --- a/Documentation/devicetree/bindings/gpio/gpio.txt +++ b/Documentation/devicetree/bindings/gpio/gpio.txt @@ -13,13 +13,22 @@ properties, each containing a 'gpio-list': gpio-specifier : Array of #gpio-cells specifying specific gpio (controller specific) -GPIO properties should be named "[<name>-]gpios". The exact -meaning of each gpios property must be documented in the device tree -binding for each device. +GPIO properties should be named "[<name>-]gpios", with <name> being the purpose +of this GPIO for the device. While a non-existent <name> is considered valid +for compatibility reasons (resolving to the "gpios" property), it is not allowed +for new bindings. -For example, the following could be used to describe GPIO pins used -as chip select lines; with chip selects 0, 1 and 3 populated, and chip -select 2 left empty: +GPIO properties can contain one or more GPIO phandles, but only in exceptional +cases should they contain more than one. If your device uses several GPIOs with +distinct functions, reference each of them under its own property, giving it a +meaningful name. The only case where an array of GPIOs is accepted is when +several GPIOs serve the same function (e.g. a parallel data line). + +The exact purpose of each gpios property must be documented in the device tree +binding of the device. + +The following example could be used to describe GPIO pins used as device enable +and bit-banged data signals: gpio1: gpio1 { gpio-controller @@ -30,10 +39,12 @@ select 2 left empty: #gpio-cells = <1>; }; [...] - chipsel-gpios = <&gpio1 12 0>, - <&gpio1 13 0>, - <0>, /* holes are permitted, means no GPIO 2 */ - <&gpio2 2>; + + enable-gpios = <&gpio2 2>; + data-gpios = <&gpio1 12 0>, + <&gpio1 13 0>, + <&gpio1 14 0>, + <&gpio1 15 0>; Note that gpio-specifier length is controller dependent. In the above example, &gpio1 uses 2 cells to specify a gpio, while &gpio2 @@ -42,16 +53,17 @@ only uses one. gpio-specifier may encode: bank, pin position inside the bank, whether pin is open-drain and whether pin is logically inverted. Exact meaning of each specifier cell is controller specific, and must -be documented in the device tree binding for the device. +be documented in the device tree binding for the device. Use the macros +defined in include/dt-bindings/gpio/gpio.h whenever possible: Example of a node using GPIOs: node { - gpios = <&qe_pio_e 18 0>; + enable-gpios = <&qe_pio_e 18 GPIO_ACTIVE_HIGH>; }; -In this example gpio-specifier is "18 0" and encodes GPIO pin number, -and GPIO flags as accepted by the "qe_pio_e" gpio-controller. +GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes +GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller. 1.1) GPIO specifier best practices ---------------------------------- |