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-rw-r--r--Documentation/devicetree/bindings/gpio/gpio.txt55
1 files changed, 30 insertions, 25 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index d933af370697..6cec6ff20d2e 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -75,23 +75,36 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
gpio-controller;
};
-2.1) gpio-controller and pinctrl subsystem
-------------------------------------------
+2.1) gpio- and pin-controller interaction
+-----------------------------------------
-gpio-controller on a SOC might be tightly coupled with the pinctrl
-subsystem, in the sense that the pins can be used by other functions
-together with optional gpio feature.
+Some or all of the GPIOs provided by a GPIO controller may be routed to pins
+on the package via a pin controller. This allows muxing those pins between
+GPIO and other functions.
-While the pin allocation is totally managed by the pin ctrl subsystem,
-gpio (under gpiolib) is still maintained by gpio drivers. It may happen
-that different pin ranges in a SoC is managed by different gpio drivers.
+It is useful to represent which GPIOs correspond to which pins on which pin
+controllers. The gpio-ranges property described below represents this, and
+contains information structures as follows:
-This makes it logical to let gpio drivers announce their pin ranges to
-the pin ctrl subsystem and call 'pinctrl_request_gpio' in order to
-request the corresponding pin before any gpio usage.
+ gpio-range-list ::= <single-gpio-range> [gpio-range-list]
+ single-gpio-range ::=
+ <pinctrl-phandle> <gpio-base> <pinctrl-base> <count>
+ gpio-phandle : phandle to pin controller node.
+ gpio-base : Base GPIO ID in the GPIO controller
+ pinctrl-base : Base pinctrl pin ID in the pin controller
+ count : The number of GPIOs/pins in this range
-For this, the gpio controller can use a pinctrl phandle and pins to
-announce the pinrange to the pin ctrl subsystem. For example,
+The "pin controller node" mentioned above must conform to the bindings
+described in ../pinctrl/pinctrl-bindings.txt.
+
+Previous versions of this binding required all pin controller nodes that
+were referenced by any gpio-ranges property to contain a property named
+#gpio-range-cells with value <3>. This requirement is now deprecated.
+However, that property may still exist in older device trees for
+compatibility reasons, and would still be required even in new device
+trees that need to be compatible with older software.
+
+Example:
qe_pio_e: gpio-controller@1460 {
#gpio-cells = <2>;
@@ -99,16 +112,8 @@ announce the pinrange to the pin ctrl subsystem. For example,
reg = <0x1460 0x18>;
gpio-controller;
gpio-ranges = <&pinctrl1 0 20 10>, <&pinctrl2 10 50 20>;
+ };
- }
-
-where,
- &pinctrl1 and &pinctrl2 is the phandle to the pinctrl DT node.
-
- Next values specify the base pin and number of pins for the range
- handled by 'qe_pio_e' gpio. In the given example from base pin 20 to
- pin 29 under pinctrl1 with gpio offset 0 and pin 50 to pin 69 under
- pinctrl2 with gpio offset 10 is handled by this gpio controller.
-
-The pinctrl node must have "#gpio-range-cells" property to show number of
-arguments to pass with phandle from gpio controllers node.
+Here, a single GPIO controller has GPIOs 0..9 routed to pin controller
+pinctrl1's pins 20..29, and GPIOs 10..19 routed to pin controller pinctrl2's
+pins 50..59.

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