1/*
2 * Copyright (C) 2013 STMicroelectronics Limited
3 * Author: Stephen Gallimore <stephen.gallimore@st.com>
4 *
5 * Inspired by mach-imx/src.c
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 */
12#include <linux/kernel.h>
13#include <linux/platform_device.h>
14#include <linux/module.h>
15#include <linux/err.h>
16#include <linux/types.h>
17#include <linux/of_device.h>
18#include <linux/regmap.h>
19#include <linux/mfd/syscon.h>
20
21#include "reset-syscfg.h"
22
23/**
24 * Reset channel regmap configuration
25 *
26 * @reset: regmap field for the channel's reset bit.
27 * @ack: regmap field for the channel's ack bit (optional).
28 */
29struct syscfg_reset_channel {
30	struct regmap_field *reset;
31	struct regmap_field *ack;
32};
33
34/**
35 * A reset controller which groups together a set of related reset bits, which
36 * may be located in different system configuration registers.
37 *
38 * @rst: base reset controller structure.
39 * @active_low: are the resets in this controller active low, i.e. clearing
40 *              the reset bit puts the hardware into reset.
41 * @channels: An array of reset channels for this controller.
42 */
43struct syscfg_reset_controller {
44	struct reset_controller_dev rst;
45	bool active_low;
46	struct syscfg_reset_channel *channels;
47};
48
49#define to_syscfg_reset_controller(_rst) \
50	container_of(_rst, struct syscfg_reset_controller, rst)
51
52static int syscfg_reset_program_hw(struct reset_controller_dev *rcdev,
53				   unsigned long idx, int assert)
54{
55	struct syscfg_reset_controller *rst = to_syscfg_reset_controller(rcdev);
56	const struct syscfg_reset_channel *ch;
57	u32 ctrl_val = rst->active_low ? !assert : !!assert;
58	int err;
59
60	if (idx >= rcdev->nr_resets)
61		return -EINVAL;
62
63	ch = &rst->channels[idx];
64
65	err = regmap_field_write(ch->reset, ctrl_val);
66	if (err)
67		return err;
68
69	if (ch->ack) {
70		unsigned long timeout = jiffies + msecs_to_jiffies(1000);
71		u32 ack_val;
72
73		while (true) {
74			err = regmap_field_read(ch->ack, &ack_val);
75			if (err)
76				return err;
77
78			if (ack_val == ctrl_val)
79				break;
80
81			if (time_after(jiffies, timeout))
82				return -ETIME;
83
84			cpu_relax();
85		}
86	}
87
88	return 0;
89}
90
91static int syscfg_reset_assert(struct reset_controller_dev *rcdev,
92			       unsigned long idx)
93{
94	return syscfg_reset_program_hw(rcdev, idx, true);
95}
96
97static int syscfg_reset_deassert(struct reset_controller_dev *rcdev,
98				 unsigned long idx)
99{
100	return syscfg_reset_program_hw(rcdev, idx, false);
101}
102
103static int syscfg_reset_dev(struct reset_controller_dev *rcdev,
104			    unsigned long idx)
105{
106	int err = syscfg_reset_assert(rcdev, idx);
107	if (err)
108		return err;
109
110	return syscfg_reset_deassert(rcdev, idx);
111}
112
113static struct reset_control_ops syscfg_reset_ops = {
114	.reset    = syscfg_reset_dev,
115	.assert   = syscfg_reset_assert,
116	.deassert = syscfg_reset_deassert,
117};
118
119static int syscfg_reset_controller_register(struct device *dev,
120				const struct syscfg_reset_controller_data *data)
121{
122	struct syscfg_reset_controller *rc;
123	size_t size;
124	int i, err;
125
126	rc = devm_kzalloc(dev, sizeof(*rc), GFP_KERNEL);
127	if (!rc)
128		return -ENOMEM;
129
130	size = sizeof(struct syscfg_reset_channel) * data->nr_channels;
131
132	rc->channels = devm_kzalloc(dev, size, GFP_KERNEL);
133	if (!rc->channels)
134		return -ENOMEM;
135
136	rc->rst.ops = &syscfg_reset_ops,
137	rc->rst.of_node = dev->of_node;
138	rc->rst.nr_resets = data->nr_channels;
139	rc->active_low = data->active_low;
140
141	for (i = 0; i < data->nr_channels; i++) {
142		struct regmap *map;
143		struct regmap_field *f;
144		const char *compatible = data->channels[i].compatible;
145
146		map = syscon_regmap_lookup_by_compatible(compatible);
147		if (IS_ERR(map))
148			return PTR_ERR(map);
149
150		f = devm_regmap_field_alloc(dev, map, data->channels[i].reset);
151		if (IS_ERR(f))
152			return PTR_ERR(f);
153
154		rc->channels[i].reset = f;
155
156		if (!data->wait_for_ack)
157			continue;
158
159		f = devm_regmap_field_alloc(dev, map, data->channels[i].ack);
160		if (IS_ERR(f))
161			return PTR_ERR(f);
162
163		rc->channels[i].ack = f;
164	}
165
166	err = reset_controller_register(&rc->rst);
167	if (!err)
168		dev_info(dev, "registered\n");
169
170	return err;
171}
172
173int syscfg_reset_probe(struct platform_device *pdev)
174{
175	struct device *dev = pdev ? &pdev->dev : NULL;
176	const struct of_device_id *match;
177
178	if (!dev || !dev->driver)
179		return -ENODEV;
180
181	match = of_match_device(dev->driver->of_match_table, dev);
182	if (!match || !match->data)
183		return -EINVAL;
184
185	return syscfg_reset_controller_register(dev, match->data);
186}
187