summaryrefslogtreecommitdiffstats
path: root/drivers/char/hw_random/ba431-rng.c
blob: 5b7ca0416490a27b78557b9939ebd80e3cd4706b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Silex Insight

#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>

#define BA431_RESET_DELAY			1 /* usec */
#define BA431_RESET_READ_STATUS_TIMEOUT		1000 /* usec */
#define BA431_RESET_READ_STATUS_INTERVAL	10 /* usec */
#define BA431_READ_RETRY_INTERVAL		1 /* usec */

#define BA431_REG_CTRL				0x00
#define BA431_REG_FIFO_LEVEL			0x04
#define BA431_REG_STATUS			0x30
#define BA431_REG_FIFODATA			0x80

#define BA431_CTRL_ENABLE			BIT(0)
#define BA431_CTRL_SOFTRESET			BIT(8)

#define BA431_STATUS_STATE_MASK			(BIT(1) | BIT(2) | BIT(3))
#define BA431_STATUS_STATE_OFFSET		1

enum ba431_state {
	BA431_STATE_RESET,
	BA431_STATE_STARTUP,
	BA431_STATE_FIFOFULLON,
	BA431_STATE_FIFOFULLOFF,
	BA431_STATE_RUNNING,
	BA431_STATE_ERROR
};

struct ba431_trng {
	struct device *dev;
	void __iomem *base;
	struct hwrng rng;
	atomic_t reset_pending;
	struct work_struct reset_work;
};

static inline u32 ba431_trng_read_reg(struct ba431_trng *ba431, u32 reg)
{
	return ioread32(ba431->base + reg);
}

static inline void ba431_trng_write_reg(struct ba431_trng *ba431, u32 reg,
					u32 val)
{
	iowrite32(val, ba431->base + reg);
}

static inline enum ba431_state ba431_trng_get_state(struct ba431_trng *ba431)
{
	u32 status = ba431_trng_read_reg(ba431, BA431_REG_STATUS);

	return (status & BA431_STATUS_STATE_MASK) >> BA431_STATUS_STATE_OFFSET;
}

static int ba431_trng_is_in_error(struct ba431_trng *ba431)
{
	enum ba431_state state = ba431_trng_get_state(ba431);

	if ((state < BA431_STATE_STARTUP) ||
	    (state >= BA431_STATE_ERROR))
		return 1;

	return 0;
}

static int ba431_trng_reset(struct ba431_trng *ba431)
{
	int ret;

	/* Disable interrupts, random generation and enable the softreset */
	ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_SOFTRESET);
	udelay(BA431_RESET_DELAY);
	ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_ENABLE);

	/* Wait until the state changed */
	if (readx_poll_timeout(ba431_trng_is_in_error, ba431, ret, !ret,
			       BA431_RESET_READ_STATUS_INTERVAL,
			       BA431_RESET_READ_STATUS_TIMEOUT)) {
		dev_err(ba431->dev, "reset failed (state: %d)\n",
			ba431_trng_get_state(ba431));
		return -ETIMEDOUT;
	}

	dev_info(ba431->dev, "reset done\n");

	return 0;
}

static void ba431_trng_reset_work(struct work_struct *work)
{
	struct ba431_trng *ba431 = container_of(work, struct ba431_trng,
						reset_work);
	ba431_trng_reset(ba431);
	atomic_set(&ba431->reset_pending, 0);
}

static void ba431_trng_schedule_reset(struct ba431_trng *ba431)
{
	if (atomic_cmpxchg(&ba431->reset_pending, 0, 1))
		return;

	schedule_work(&ba431->reset_work);
}

static int ba431_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
	struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
	u32 *data = buf;
	unsigned int level, i;
	int n = 0;

	while (max > 0) {
		level = ba431_trng_read_reg(ba431, BA431_REG_FIFO_LEVEL);
		if (!level) {
			if (ba431_trng_is_in_error(ba431)) {
				ba431_trng_schedule_reset(ba431);
				break;
			}

			if (!wait)
				break;

			udelay(BA431_READ_RETRY_INTERVAL);
			continue;
		}

		i = level;
		do {
			data[n++] = ba431_trng_read_reg(ba431,
							BA431_REG_FIFODATA);
			max -= sizeof(*data);
		} while (--i && (max > 0));

		if (ba431_trng_is_in_error(ba431)) {
			n -= (level - i);
			ba431_trng_schedule_reset(ba431);
			break;
		}
	}

	n *= sizeof(data);
	return (n || !wait) ? n : -EIO;
}

static void ba431_trng_cleanup(struct hwrng *rng)
{
	struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);

	ba431_trng_write_reg(ba431, BA431_REG_CTRL, 0);
	cancel_work_sync(&ba431->reset_work);
}

static int ba431_trng_init(struct hwrng *rng)
{
	struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);

	return ba431_trng_reset(ba431);
}

static int ba431_trng_probe(struct platform_device *pdev)
{
	struct ba431_trng *ba431;
	int ret;

	ba431 = devm_kzalloc(&pdev->dev, sizeof(*ba431), GFP_KERNEL);
	if (!ba431)
		return -ENOMEM;

	ba431->dev = &pdev->dev;

	ba431->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(ba431->base))
		return PTR_ERR(ba431->base);

	atomic_set(&ba431->reset_pending, 0);
	INIT_WORK(&ba431->reset_work, ba431_trng_reset_work);
	ba431->rng.name = pdev->name;
	ba431->rng.init = ba431_trng_init;
	ba431->rng.cleanup = ba431_trng_cleanup;
	ba431->rng.read = ba431_trng_read;

	platform_set_drvdata(pdev, ba431);

	ret = devm_hwrng_register(&pdev->dev, &ba431->rng);
	if (ret) {
		dev_err(&pdev->dev, "BA431 registration failed (%d)\n", ret);
		return ret;
	}

	dev_info(&pdev->dev, "BA431 TRNG registered\n");

	return 0;
}

static const struct of_device_id ba431_trng_dt_ids[] = {
	{ .compatible = "silex-insight,ba431-rng", .data = NULL },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids);

static struct platform_driver ba431_trng_driver = {
	.driver = {
		.name = "ba431-rng",
		.of_match_table = ba431_trng_dt_ids,
	},
	.probe = ba431_trng_probe,
};

module_platform_driver(ba431_trng_driver);

MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>");
MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431");
MODULE_LICENSE("GPL");