1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2020 Silex Insight
3
4 #include <linux/delay.h>
5 #include <linux/hw_random.h>
6 #include <linux/io.h>
7 #include <linux/iopoll.h>
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/platform_device.h>
11 #include <linux/workqueue.h>
12
13 #define BA431_RESET_DELAY 1 /* usec */
14 #define BA431_RESET_READ_STATUS_TIMEOUT 1000 /* usec */
15 #define BA431_RESET_READ_STATUS_INTERVAL 10 /* usec */
16 #define BA431_READ_RETRY_INTERVAL 1 /* usec */
17
18 #define BA431_REG_CTRL 0x00
19 #define BA431_REG_FIFO_LEVEL 0x04
20 #define BA431_REG_STATUS 0x30
21 #define BA431_REG_FIFODATA 0x80
22
23 #define BA431_CTRL_ENABLE BIT(0)
24 #define BA431_CTRL_SOFTRESET BIT(8)
25
26 #define BA431_STATUS_STATE_MASK (BIT(1) | BIT(2) | BIT(3))
27 #define BA431_STATUS_STATE_OFFSET 1
28
29 enum ba431_state {
30 BA431_STATE_RESET,
31 BA431_STATE_STARTUP,
32 BA431_STATE_FIFOFULLON,
33 BA431_STATE_FIFOFULLOFF,
34 BA431_STATE_RUNNING,
35 BA431_STATE_ERROR
36 };
37
38 struct ba431_trng {
39 struct device *dev;
40 void __iomem *base;
41 struct hwrng rng;
42 atomic_t reset_pending;
43 struct work_struct reset_work;
44 };
45
ba431_trng_read_reg(struct ba431_trng * ba431,u32 reg)46 static inline u32 ba431_trng_read_reg(struct ba431_trng *ba431, u32 reg)
47 {
48 return ioread32(ba431->base + reg);
49 }
50
ba431_trng_write_reg(struct ba431_trng * ba431,u32 reg,u32 val)51 static inline void ba431_trng_write_reg(struct ba431_trng *ba431, u32 reg,
52 u32 val)
53 {
54 iowrite32(val, ba431->base + reg);
55 }
56
ba431_trng_get_state(struct ba431_trng * ba431)57 static inline enum ba431_state ba431_trng_get_state(struct ba431_trng *ba431)
58 {
59 u32 status = ba431_trng_read_reg(ba431, BA431_REG_STATUS);
60
61 return (status & BA431_STATUS_STATE_MASK) >> BA431_STATUS_STATE_OFFSET;
62 }
63
ba431_trng_is_in_error(struct ba431_trng * ba431)64 static int ba431_trng_is_in_error(struct ba431_trng *ba431)
65 {
66 enum ba431_state state = ba431_trng_get_state(ba431);
67
68 if ((state < BA431_STATE_STARTUP) ||
69 (state >= BA431_STATE_ERROR))
70 return 1;
71
72 return 0;
73 }
74
ba431_trng_reset(struct ba431_trng * ba431)75 static int ba431_trng_reset(struct ba431_trng *ba431)
76 {
77 int ret;
78
79 /* Disable interrupts, random generation and enable the softreset */
80 ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_SOFTRESET);
81 udelay(BA431_RESET_DELAY);
82 ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_ENABLE);
83
84 /* Wait until the state changed */
85 if (readx_poll_timeout(ba431_trng_is_in_error, ba431, ret, !ret,
86 BA431_RESET_READ_STATUS_INTERVAL,
87 BA431_RESET_READ_STATUS_TIMEOUT)) {
88 dev_err(ba431->dev, "reset failed (state: %d)\n",
89 ba431_trng_get_state(ba431));
90 return -ETIMEDOUT;
91 }
92
93 dev_info(ba431->dev, "reset done\n");
94
95 return 0;
96 }
97
ba431_trng_reset_work(struct work_struct * work)98 static void ba431_trng_reset_work(struct work_struct *work)
99 {
100 struct ba431_trng *ba431 = container_of(work, struct ba431_trng,
101 reset_work);
102 ba431_trng_reset(ba431);
103 atomic_set(&ba431->reset_pending, 0);
104 }
105
ba431_trng_schedule_reset(struct ba431_trng * ba431)106 static void ba431_trng_schedule_reset(struct ba431_trng *ba431)
107 {
108 if (atomic_cmpxchg(&ba431->reset_pending, 0, 1))
109 return;
110
111 schedule_work(&ba431->reset_work);
112 }
113
ba431_trng_read(struct hwrng * rng,void * buf,size_t max,bool wait)114 static int ba431_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
115 {
116 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
117 u32 *data = buf;
118 unsigned int level, i;
119 int n = 0;
120
121 while (max > 0) {
122 level = ba431_trng_read_reg(ba431, BA431_REG_FIFO_LEVEL);
123 if (!level) {
124 if (ba431_trng_is_in_error(ba431)) {
125 ba431_trng_schedule_reset(ba431);
126 break;
127 }
128
129 if (!wait)
130 break;
131
132 udelay(BA431_READ_RETRY_INTERVAL);
133 continue;
134 }
135
136 i = level;
137 do {
138 data[n++] = ba431_trng_read_reg(ba431,
139 BA431_REG_FIFODATA);
140 max -= sizeof(*data);
141 } while (--i && (max > 0));
142
143 if (ba431_trng_is_in_error(ba431)) {
144 n -= (level - i);
145 ba431_trng_schedule_reset(ba431);
146 break;
147 }
148 }
149
150 n *= sizeof(data);
151 return (n || !wait) ? n : -EIO;
152 }
153
ba431_trng_cleanup(struct hwrng * rng)154 static void ba431_trng_cleanup(struct hwrng *rng)
155 {
156 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
157
158 ba431_trng_write_reg(ba431, BA431_REG_CTRL, 0);
159 cancel_work_sync(&ba431->reset_work);
160 }
161
ba431_trng_init(struct hwrng * rng)162 static int ba431_trng_init(struct hwrng *rng)
163 {
164 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
165
166 return ba431_trng_reset(ba431);
167 }
168
ba431_trng_probe(struct platform_device * pdev)169 static int ba431_trng_probe(struct platform_device *pdev)
170 {
171 struct ba431_trng *ba431;
172 int ret;
173
174 ba431 = devm_kzalloc(&pdev->dev, sizeof(*ba431), GFP_KERNEL);
175 if (!ba431)
176 return -ENOMEM;
177
178 ba431->dev = &pdev->dev;
179
180 ba431->base = devm_platform_ioremap_resource(pdev, 0);
181 if (IS_ERR(ba431->base))
182 return PTR_ERR(ba431->base);
183
184 atomic_set(&ba431->reset_pending, 0);
185 INIT_WORK(&ba431->reset_work, ba431_trng_reset_work);
186 ba431->rng.name = pdev->name;
187 ba431->rng.init = ba431_trng_init;
188 ba431->rng.cleanup = ba431_trng_cleanup;
189 ba431->rng.read = ba431_trng_read;
190
191 ret = devm_hwrng_register(&pdev->dev, &ba431->rng);
192 if (ret)
193 return dev_err_probe(&pdev->dev, ret, "BA431 registration failed\n");
194
195 dev_info(&pdev->dev, "BA431 TRNG registered\n");
196
197 return 0;
198 }
199
200 static const struct of_device_id ba431_trng_dt_ids[] = {
201 { .compatible = "silex-insight,ba431-rng" },
202 { /* sentinel */ }
203 };
204 MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids);
205
206 static struct platform_driver ba431_trng_driver = {
207 .driver = {
208 .name = "ba431-rng",
209 .of_match_table = ba431_trng_dt_ids,
210 },
211 .probe = ba431_trng_probe,
212 };
213
214 module_platform_driver(ba431_trng_driver);
215
216 MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>");
217 MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431");
218 MODULE_LICENSE("GPL");
219