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Stephen Warren89c1e2d2016-06-17 09:43:58 -06001/*
2 * Copyright (c) 2016, NVIDIA CORPORATION.
3 *
4 * SPDX-License-Identifier: GPL-2.0
5 */
6
7#ifndef _RESET_H
8#define _RESET_H
9
10/**
11 * A reset is a hardware signal indicating that a HW module (or IP block, or
12 * sometimes an entire off-CPU chip) reset all of its internal state to some
13 * known-good initial state. Drivers will often reset HW modules when they
14 * begin execution to ensure that hardware correctly responds to all requests,
15 * or in response to some error condition. Reset signals are often controlled
16 * externally to the HW module being reset, by an entity this API calls a reset
17 * controller. This API provides a standard means for drivers to request that
18 * reset controllers set or clear reset signals.
19 *
20 * A driver that implements UCLASS_RESET is a reset controller or provider. A
21 * controller will often implement multiple separate reset signals, since the
22 * hardware it manages often has this capability. reset-uclass.h describes the
23 * interface which reset controllers must implement.
24 *
25 * Reset consumers/clients are the HW modules affected by reset signals. This
26 * header file describes the API used by drivers for those HW modules.
27 */
28
29struct udevice;
30
31/**
32 * struct reset_ctl - A handle to (allowing control of) a single reset signal.
33 *
34 * Clients provide storage for reset control handles. The content of the
35 * structure is managed solely by the reset API and reset drivers. A reset
36 * control struct is initialized by "get"ing the reset control struct. The
37 * reset control struct is passed to all other reset APIs to identify which
38 * reset signal to operate upon.
39 *
40 * @dev: The device which implements the reset signal.
41 * @id: The reset signal ID within the provider.
42 *
43 * Currently, the reset API assumes that a single integer ID is enough to
44 * identify and configure any reset signal for any reset provider. If this
45 * assumption becomes invalid in the future, the struct could be expanded to
46 * either (a) add more fields to allow reset providers to store additional
47 * information, or (b) replace the id field with an opaque pointer, which the
48 * provider would dynamically allocated during its .of_xlate op, and process
49 * during is .request op. This may require the addition of an extra op to clean
50 * up the allocation.
51 */
52struct reset_ctl {
53 struct udevice *dev;
54 /*
55 * Written by of_xlate. We assume a single id is enough for now. In the
56 * future, we might add more fields here.
57 */
58 unsigned long id;
59};
60
61/**
62 * reset_get_by_index - Get/request a reset signal by integer index.
63 *
64 * This looks up and requests a reset signal. The index is relative to the
65 * client device; each device is assumed to have n reset signals associated
66 * with it somehow, and this function finds and requests one of them. The
67 * mapping of client device reset signal indices to provider reset signals may
68 * be via device-tree properties, board-provided mapping tables, or some other
69 * mechanism.
70 *
71 * @dev: The client device.
72 * @index: The index of the reset signal to request, within the client's
73 * list of reset signals.
74 * @reset_ctl A pointer to a reset control struct to initialize.
75 * @return 0 if OK, or a negative error code.
76 */
77int reset_get_by_index(struct udevice *dev, int index,
78 struct reset_ctl *reset_ctl);
79
80/**
81 * reset_get_by_name - Get/request a reset signal by name.
82 *
83 * This looks up and requests a reset signal. The name is relative to the
84 * client device; each device is assumed to have n reset signals associated
85 * with it somehow, and this function finds and requests one of them. The
86 * mapping of client device reset signal names to provider reset signal may be
87 * via device-tree properties, board-provided mapping tables, or some other
88 * mechanism.
89 *
90 * @dev: The client device.
91 * @name: The name of the reset signal to request, within the client's
92 * list of reset signals.
93 * @reset_ctl: A pointer to a reset control struct to initialize.
94 * @return 0 if OK, or a negative error code.
95 */
96int reset_get_by_name(struct udevice *dev, const char *name,
97 struct reset_ctl *reset_ctl);
98
99/**
100 * reset_free - Free a previously requested reset signal.
101 *
102 * @reset_ctl: A reset control struct that was previously successfully
103 * requested by reset_get_by_*().
104 * @return 0 if OK, or a negative error code.
105 */
106int reset_free(struct reset_ctl *reset_ctl);
107
108/**
109 * reset_assert - Assert a reset signal.
110 *
111 * This function will assert the specified reset signal, thus resetting the
112 * affected HW module(s). Depending on the reset controller hardware, the reset
113 * signal will either stay asserted until reset_deassert() is called, or the
114 * hardware may autonomously clear the reset signal itself.
115 *
116 * @reset_ctl: A reset control struct that was previously successfully
117 * requested by reset_get_by_*().
118 * @return 0 if OK, or a negative error code.
119 */
120int reset_assert(struct reset_ctl *reset_ctl);
121
122/**
123 * reset_deassert - Deassert a reset signal.
124 *
125 * This function will deassert the specified reset signal, thus releasing the
126 * affected HW modules() from reset, and allowing them to continue normal
127 * operation.
128 *
129 * @reset_ctl: A reset control struct that was previously successfully
130 * requested by reset_get_by_*().
131 * @return 0 if OK, or a negative error code.
132 */
133int reset_deassert(struct reset_ctl *reset_ctl);
134
135#endif