1 * Open PIC Binding
2
3 This binding specifies what properties must be available in the device tree
4 representation of an Open PIC compliant interrupt controller. This binding is
5 based on the binding defined for Open PIC in [1] and is a superset of that
6 binding.
7
8 Required properties:
9
10 NOTE: Many of these descriptions were paraphrased here from [1] to aid
11 readability.
12
13 - compatible: Specifies the compatibility list for the PIC. The type
14 shall be <string> and the value shall include "open-pic".
15
16 - reg: Specifies the base physical address(s) and size(s) of this
17 PIC's addressable register space. The type shall be <prop-encoded-array>.
18
19 - interrupt-controller: The presence of this property identifies the node
20 as an Open PIC. No property value shall be defined.
21
22 - #interrupt-cells: Specifies the number of cells needed to encode an
23 interrupt source. The type shall be a <u32> and the value shall be 2.
24
25 - #address-cells: Specifies the number of cells needed to encode an
26 address. The type shall be <u32> and the value shall be 0. As such,
27 'interrupt-map' nodes do not have to specify a parent unit address.
28
29 Optional properties:
30
31 - pic-no-reset: The presence of this property indicates that the PIC
32 shall not be reset during runtime initialization. No property value shall
33 be defined. The presence of this property also mandates that any
34 initialization related to interrupt sources shall be limited to sources
35 explicitly referenced in the device tree.
36
37 * Interrupt Specifier Definition
38
39 Interrupt specifiers consists of 2 cells encoded as
40 follows:
41
42 - <1st-cell>: The interrupt-number that identifies the interrupt source.
43
44 - <2nd-cell>: The level-sense information, encoded as follows:
45 0 = low-to-high edge triggered
46 1 = active low level-sensitive
47 2 = active high level-sensitive
48 3 = high-to-low edge triggered
49
50 * Examples
51
52 Example 1:
53
54 /*
55 * An Open PIC interrupt controller
56 */
57 mpic: pic@40000 {
58 // This is an interrupt controller node.
59 interrupt-controller;
60
61 // No address cells so that 'interrupt-map' nodes which reference
62 // this Open PIC node do not need a parent address specifier.
63 #address-cells = <0>;
64
65 // Two cells to encode interrupt sources.
66 #interrupt-cells = <2>;
67
68 // Offset address of 0x40000 and size of 0x40000.
69 reg = <0x40000 0x40000>;
70
71 // Compatible with Open PIC.
72 compatible = "open-pic";
73
74 // The PIC shall not be reset.
75 pic-no-reset;
76 };
77
78 Example 2:
79
80 /*
81 * An interrupt generating device that is wired to an Open PIC.
82 */
83 serial0: serial@4500 {
84 // Interrupt source '42' that is active high level-sensitive.
85 // Note that there are only two cells as specified in the interrupt
86 // parent's '#interrupt-cells' property.
87 interrupts = <42 2>;
88
89 // The interrupt controller that this device is wired to.
90 interrupt-parent = <&mpic>;
91 };
92
93 * References
94
95 [1] Devicetree Specification
96 (https://www.devicetree.org/specifications/)
97
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