1= Reset Signal Device Tree Bindings =
2
3This binding is intended to represent the hardware reset signals present
4internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole
5standalone chips are most likely better represented as GPIOs, although there
6are likely to be exceptions to this rule.
7
8Hardware blocks typically receive a reset signal. This signal is generated by
9a reset provider (e.g. power management or clock module) and received by a
10reset consumer (the module being reset, or a module managing when a sub-
11ordinate module is reset). This binding exists to represent the provider and
12consumer, and provide a way to couple the two together.
13
14A reset signal is represented by the phandle of the provider, plus a reset
15specifier - a list of DT cells that represents the reset signal within the
16provider. The length (number of cells) and semantics of the reset specifier
17are dictated by the binding of the reset provider, although common schemes
18are described below.
19
20A word on where to place reset signal consumers in device tree: It is possible
21in hardware for a reset signal to affect multiple logically separate HW blocks
22at once. In this case, it would be unwise to represent this reset signal in
23the DT node of each affected HW block, since if activated, an unrelated block
24may be reset. Instead, reset signals should be represented in the DT node
25where it makes most sense to control it; this may be a bus node if all
26children of the bus are affected by the reset signal, or an individual HW
27block node for dedicated reset signals. The intent of this binding is to give
28appropriate software access to the reset signals in order to manage the HW,
29rather than to slavishly enumerate the reset signal that affects each HW
30block.
31
32= Reset providers =
33
34Required properties:
35#reset-cells:	Number of cells in a reset specifier; Typically 0 for nodes
36		with a single reset output and 1 for nodes with multiple
37		reset outputs.
38
39For example:
40
41	rst: reset-controller {
42		#reset-cells = <1>;
43	};
44
45= Reset consumers =
46
47Required properties:
48resets:		List of phandle and reset specifier pairs, one pair
49		for each reset signal that affects the device, or that the
50		device manages. Note: if the reset provider specifies '0' for
51		#reset-cells, then only the phandle portion of the pair will
52		appear.
53
54Optional properties:
55reset-names:	List of reset signal name strings sorted in the same order as
56		the resets property. Consumers drivers will use reset-names to
57		match reset signal names with reset specifiers.
58
59For example:
60
61	device {
62		resets = <&rst 20>;
63		reset-names = "reset";
64	};
65
66This represents a device with a single reset signal named "reset".
67
68	bus {
69		resets = <&rst 10> <&rst 11> <&rst 12> <&rst 11>;
70		reset-names = "i2s1", "i2s2", "dma", "mixer";
71	};
72
73This represents a bus that controls the reset signal of each of four sub-
74ordinate devices. Consider for example a bus that fails to operate unless no
75child device has reset asserted.
76