nordic,nrf-gpio-forwarder

Description

This is an abstract device responsible for forwarding pins between cores.

In nRF53 family of SoCs, GPIO pins must be explicitly forwarded by
the application core to the network core if the latter should drive them.
The purpose of this abstract device is to represent all GPIO pins that the
nRF53 application core should forward to the nRF53 network core.

Once the control over selected GPIO pins is forwarded to it, the network
core is responsible for configuring the pins and driving them as needed.

Here is an example of how a nrf-gpio-forwarder can be used with a nRF5340
combined with a nRF21540 Front-End module. Consider the following node
present in DTS file targeted for the nRF5340 network core, which defines
the details of the nRF21540 Front-End module's interface:

nrf_radio_fem: nrf21540 {
  compatible = "nordic,nrf21540-fem";
  tx-en-gpios = <&gpio0 30 GPIO_ACTIVE_HIGH>;
  rx-en-gpios = <&gpio1 11 GPIO_ACTIVE_HIGH>;
  pdn-gpios   = <&gpio1 10 GPIO_ACTIVE_HIGH>;
  mode-gpios  = <&gpio1 12 GPIO_ACTIVE_HIGH>;
};

Since the nRF21540 Front-End module should be controlled by the nRF5340
network core, all the GPIO pins used to control it must be forwarded by
the nRF5340 application core to the network core. Consider the following
nrf-gpio-forwarder node defined in DTS file targeted for the nRF5340
application core:

gpio_fwd: nrf-gpio-forwarder {
  compatible = "nordic,nrf-gpio-forwarder";
  nrf21540-gpio-if {
    gpios = <&gpio0 30 0>, <&gpio1 11 0>, <&gpio1 10 0>, <&gpio1 12 0>;
  };
};

In the above example, the nrf-gpio-forwarder node is configured to forward
control over the following GPIO pins to the network core:

  - P0.30 (matching `tx-en-gpios`)
  - P1.11 (matching `rx-en-gpios`)
  - P1.10 (matching `pdn-gpios`)
  - P1.12 (matching `mode-gpios`)

Please note that the GPIO flags provided for child nodes of the forwarder
are ignored. In order to configure the GPIOs passed to the forwarder, their
GPIO flags must be set in the matching node that these GPIOs are forwarded
to. In the above example, the GPIO flags must be set in the nrf21540 node.
They are set to 0 in the nrf-gpio-forwarder node as they are ignored anyway.

Child nodes for the forwarder can be defined independently by multiple DTS
files. They are merged into a single node with multiple child nodes when
processing devicetree for an application build. However, in order for that
to happen, names of the child nodes must be unique in the scope of a single
nrf-gpio-forwarder instance.

Properties

Top level properties

These property descriptions apply to “nordic,nrf-gpio-forwarder” nodes themselves. This page also describes child node properties in the following sections.

Properties not inherited from the base binding file.

(None)

Properties inherited from the base binding file, which defines common properties that may be set on many nodes. Not all of these may apply to the “nordic,nrf-gpio-forwarder” compatible.

Name	Type	Details
`status`	`string`	indicates the operational status of a device Legal values: `'ok'`, `'okay'`, `'disabled'`, `'reserved'`, `'fail'`, `'fail-sss'` See Important properties for more information.
`compatible`	`string-array`	compatible strings This property is required. See Important properties for more information.
`reg`	`array`	register space See Important properties for more information.
`reg-names`	`string-array`	name of each register space
`interrupts`	`array`	interrupts for device See Important properties for more information.
`interrupts-extended`	`compound`	extended interrupt specifier for device
`interrupt-names`	`string-array`	name of each interrupt
`interrupt-parent`	`phandle`	phandle to interrupt controller node
`label`	`string`	Human readable string describing the device (used as device_get_binding() argument) See Important properties for more information.
`clocks`	`phandle-array`	Clock gate information
`clock-names`	`string-array`	name of each clock
`#address-cells`	`int`	number of address cells in reg property
`#size-cells`	`int`	number of size cells in reg property
`dmas`	`phandle-array`	DMA channels specifiers
`dma-names`	`string-array`	Provided names of DMA channel specifiers
`io-channels`	`phandle-array`	IO channels specifiers
`io-channel-names`	`string-array`	Provided names of IO channel specifiers
`mboxes`	`phandle-array`	mailbox / IPM channels specifiers
`mbox-names`	`string-array`	Provided names of mailbox / IPM channel specifiers
`wakeup-source`	`boolean`	Property to identify that a device can be used as wake up source. When this property is provided a specific flag is set into the device that tells the system that the device is capable of wake up the system. Wake up capable devices are disabled (interruptions will not wake up the system) by default but they can be enabled at runtime if necessary.
`power-domain`	`phandle`	Power domain the device belongs to. The device will be notified when the power domain it belongs to is either suspended or resumed.

Child node properties

Name

Type

Details

gpios

phandle-array

Array of GPIOs to be forwarded. Note that GPIO flags provided for
elements of this array are ignored. In order to configure the GPIOs
from this array, their GPIO flags must be set in the matching
node that these GPIOs are forwarded to.

This property is required.