device-tree-bindings/gpio/gpio.txt

1 Specifying GPIO information for devices
8 properties, each containing a 'gpio-list':
10 	gpio-list ::= <single-gpio> [gpio-list]
11 	single-gpio ::= <gpio-phandle> <gpio-specifier>
12 	gpio-phandle : phandle to gpio controller node
13 	gpio-specifier : Array of #gpio-cells specifying specific gpio
16 GPIO properties should be named "[<name>-]gpios", with <name> being the purpose
17 of this GPIO for the device. While a non-existent <name> is considered valid
21 GPIO properties can contain one or more GPIO phandles, but only in exceptional
30 The following example could be used to describe GPIO pins used as device enable
34 		gpio-controller
35 		 #gpio-cells = <2>;
38 		gpio-controller
39 		 #gpio-cells = <1>;
49 Note that gpio-specifier length is controller dependent.  In the
50 above example, &gpio1 uses 2 cells to specify a gpio, while &gpio2
53 gpio-specifier may encode: bank, pin position inside the bank,
57 defined in include/dt-bindings/gpio/gpio.h whenever possible:
65 GPIO_ACTIVE_HIGH is 0, so in this example gpio-specifier is "18 0" and encodes
66 GPIO pin number, and GPIO flags as accepted by the "qe_pio_e" gpio-controller.
68 1.1) GPIO specifier best practices
71 A gpio-specifier should contain a flag indicating the GPIO polarity; active-
75 The gpio-specifier's polarity flag should represent the physical level at the
76 GPIO controller that achieves (or represents, for inputs) a logically asserted
79 the GPIO controller and the device, then the gpio-specifier will represent the
97 In particular, the polarity cannot be derived from the gpio-specifier, since
105 in the binding. The gpio-specifier should represent the polarity of the signal
106 (at the GPIO controller) assuming that the device is configured for this
109 responsible for correctly interpreting (inverting) the GPIO signal at the GPIO
112 2) gpio-controller nodes
115 Every GPIO controller node must contain both an empty "gpio-controller"
116 property, and a #gpio-cells integer property, which indicates the number of
117 cells in a gpio-specifier.
119 Example of two SOC GPIO banks defined as gpio-controller nodes:
121 	qe_pio_a: gpio-controller@1400 {
124 		gpio-controller;
125 		#gpio-cells = <2>;
128 	qe_pio_e: gpio-controller@1460 {
131 		gpio-controller;
132 		#gpio-cells = <2>;
135 2.1) gpio- and pin-controller interaction
138 Some or all of the GPIOs provided by a GPIO controller may be routed to pins
140 GPIO and other functions.
143 controllers. The gpio-ranges property described below represents this, and
146 	gpio-range-list ::= <single-gpio-range> [gpio-range-list]
147 	single-gpio-range ::= <numeric-gpio-range> | <named-gpio-range>
148 	numeric-gpio-range ::=
149 			<pinctrl-phandle> <gpio-base> <pinctrl-base> <count>
150 	named-gpio-range ::= <pinctrl-phandle> <gpio-base> '<0 0>'
152 	gpio-base : Base GPIO ID in the GPIO controller
159 In case named gpio ranges are used (ranges with both <pinctrl-base> and
160 <count> set to 0), the property gpio-ranges-group-names contains one string
161 for every single-gpio-range in gpio-ranges:
163 	gpiorange-name : Name of the pingroup associated to the GPIO range in
173 were referenced by any gpio-ranges property to contain a property named
174 #gpio-range-cells with value <3>. This requirement is now deprecated.
181 	qe_pio_e: gpio-controller@1460 {
182 		#gpio-cells = <2>;
185 		gpio-controller;
186 		gpio-ranges = <&pinctrl1 0 20 10>, <&pinctrl2 10 50 20>;
189 Here, a single GPIO controller has GPIOs 0..9 routed to pin controller
195 	gpio_pio_i: gpio-controller@14B0 {
196 		#gpio-cells = <2>;
199 		gpio-controller;
200 		gpio-ranges =			<&pinctrl1 0 20 10>,
204 		gpio-ranges-group-names =	"",
210 Here, three GPIO ranges are defined wrt. two pin controllers. pinctrl1 GPIO
211 ranges are defined using pin numbers whereas the GPIO ranges wrt. pinctrl2
214 3) GPIO hog definitions
217 The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
218 providing automatic GPIO request and configuration as part of the
219 gpio-controller's driver probe function.
221 Each GPIO hog definition is represented as a child node of the GPIO controller.
223 - gpio-hog:   A property specifying that this child node represents a GPIO hog.
224 - gpios:      Store the GPIO information (id, flags) for the GPIO to
227               ! Not yet support more than one gpio !
230 - input:      A property specifying to set the GPIO direction as input.
231 - output-low  A property specifying to set the GPIO direction as output with
233 - output-high A property specifying to set the GPIO direction as output with
237 - line-name:  The GPIO label name. If not present the node name is used.
244                 #gpio-cells = <2>;
245                 gpio-controller;
248                         gpio-hog;
253                         gpio-hog;
255                         line-name = "foo-bar-gpio";
260 For the above Example you can than access the gpio in your boardcode