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Diffstat (limited to 'Documentation/devicetree/bindings/gpio')
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio.txt | 55 |
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. |