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 == 100Required properties: See the pin controller driver specific documentation 101 102Optional properties: 103#pinctrl-cells: Number of pin control cells in addition to the index within the 104 pin controller device instance 105 106pinctrl-use-default: Boolean. Indicates that the OS can use the boot default 107 pin configuration. This allows using an OS that does not have a 108 driver for the pin controller. This property can be set either 109 globally for the pin controller or in child nodes for individual 110 pin group control. 111 112Pin controller devices should contain the pin configuration nodes that client 113devices reference. 114 115For example: 116 117 pincontroller { 118 ... /* Standard DT properties for the device itself elided */ 119 120 state_0_node_a { 121 ... 122 }; 123 state_1_node_a { 124 ... 125 }; 126 state_1_node_b { 127 ... 128 }; 129 } 130 131The contents of each of those pin configuration child nodes is defined 132entirely by the binding for the individual pin controller device. There 133exists no common standard for this content. The pinctrl framework only 134provides generic helper bindings that the pin controller driver can use. 135 136The pin configuration nodes need not be direct children of the pin controller 137device; they may be grandchildren, for example. Whether this is legal, and 138whether there is any interaction between the child and intermediate parent 139nodes, is again defined entirely by the binding for the individual pin 140controller device. 141 142== Generic pin multiplexing node content == 143 144See pinmux-node.yaml 145 146== Generic pin configuration node content == 147 148See pincfg-node.yaml 149