pinctrl-bindings.txt

  1== Introduction ==
  2
  3Hardware modules that control pin multiplexing or configuration parameters
  4such as pull-up/down, tri-state, drive-strength etc are designated as pin
  5controllers. Each pin controller must be represented as a node in device tree,
  6just like any other hardware module.
  7
  8Hardware modules whose signals are affected by pin configuration are
  9designated client devices. Again, each client device must be represented as a
 10node in device tree, just like any other hardware module.
 11
 12For a client device to operate correctly, certain pin controllers must
 13set up certain specific pin configurations. Some client devices need a
 14single static pin configuration, e.g. set up during initialization. Others
 15need to reconfigure pins at run-time, for example to tri-state pins when the
 16device is inactive. Hence, each client device can define a set of named
 17states. The number and names of those states is defined by the client device's
 18own binding.
 19
 20The common pinctrl bindings defined in this file provide an infrastructure
 21for client device device tree nodes to map those state names to the pin
 22configuration used by those states.
 23
 24Note that pin controllers themselves may also be client devices of themselves.
 25For example, a pin controller may set up its own "active" state when the
 26driver loads. This would allow representing a board's static pin configuration
 27in a single place, rather than splitting it across multiple client device
 28nodes. The decision to do this or not somewhat rests with the author of
 29individual board device tree files, and any requirements imposed by the
 30bindings for the individual client devices in use by that board, i.e. whether
 31they require certain specific named states for dynamic pin configuration.
 32
 33== Pinctrl client devices ==
 34
 35For each client device individually, every pin state is assigned an integer
 36ID. These numbers start at 0, and are contiguous. For each state ID, a unique
 37property exists to define the pin configuration. Each state may also be
 38assigned a name. When names are used, another property exists to map from
 39those names to the integer IDs.
 40
 41Each client device's own binding determines the set of states that must be
 42defined in its device tree node, and whether to define the set of state
 43IDs that must be provided, or whether to define the set of state names that
 44must be provided.
 45
 46Required properties:
 47pinctrl-0:	List of phandles, each pointing at a pin configuration
 48		node. These referenced pin configuration nodes must be child
 49		nodes of the pin controller that they configure. Multiple
 50		entries may exist in this list so that multiple pin
 51		controllers may be configured, or so that a state may be built
 52		from multiple nodes for a single pin controller, each
 53		contributing part of the overall configuration. See the next
 54		section of this document for details of the format of these
 55		pin configuration nodes.
 56
 57		In some cases, it may be useful to define a state, but for it
 58		to be empty. This may be required when a common IP block is
 59		used in an SoC either without a pin controller, or where the
 60		pin controller does not affect the HW module in question. If
 61		the binding for that IP block requires certain pin states to
 62		exist, they must still be defined, but may be left empty.
 63
 64Optional properties:
 65pinctrl-1:	List of phandles, each pointing at a pin configuration
 66		node within a pin controller.
 67...
 68pinctrl-n:	List of phandles, each pointing at a pin configuration
 69		node within a pin controller.
 70pinctrl-names:	The list of names to assign states. List entry 0 defines the
 71		name for integer state ID 0, list entry 1 for state ID 1, and
 72		so on.
 73
 74For example:
 75
 76	/* For a client device requiring named states */
 77	device {
 78		pinctrl-names = "active", "idle";
 79		pinctrl-0 = <&state_0_node_a>;
 80		pinctrl-1 = <&state_1_node_a>, <&state_1_node_b>;
 81	};
 82
 83	/* For the same device if using state IDs */
 84	device {
 85		pinctrl-0 = <&state_0_node_a>;
 86		pinctrl-1 = <&state_1_node_a>, <&state_1_node_b>;
 87	};
 88
 89	/*
 90	 * For an IP block whose binding supports pin configuration,
 91	 * but in use on an SoC that doesn't have any pin control hardware
 92	 */
 93	device {
 94		pinctrl-names = "active", "idle";
 95		pinctrl-0 = <>;
 96		pinctrl-1 = <>;
 97	};
 98
 99== Pin controller devices ==
100
101See pinctrl.yaml
102
103== Generic pin multiplexing node content ==
104
105See pinmux-node.yaml
106
107== Generic pin configuration node content ==
108
109See pincfg-node.yaml