1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2020 Silex Insight
4 #include <linux/delay.h>
5 #include <linux/hw_random.h>
7 #include <linux/iopoll.h>
8 #include <linux/kernel.h>
9 #include <linux/mod_devicetable.h>
10 #include <linux/module.h>
11 #include <linux/platform_device.h>
12 #include <linux/workqueue.h>
14 #define BA431_RESET_DELAY 1 /* usec */
15 #define BA431_RESET_READ_STATUS_TIMEOUT 1000 /* usec */
16 #define BA431_RESET_READ_STATUS_INTERVAL 10 /* usec */
17 #define BA431_READ_RETRY_INTERVAL 1 /* usec */
19 #define BA431_REG_CTRL 0x00
20 #define BA431_REG_FIFO_LEVEL 0x04
21 #define BA431_REG_STATUS 0x30
22 #define BA431_REG_FIFODATA 0x80
24 #define BA431_CTRL_ENABLE BIT(0)
25 #define BA431_CTRL_SOFTRESET BIT(8)
27 #define BA431_STATUS_STATE_MASK (BIT(1) | BIT(2) | BIT(3))
28 #define BA431_STATUS_STATE_OFFSET 1
33 BA431_STATE_FIFOFULLON,
34 BA431_STATE_FIFOFULLOFF,
43 atomic_t reset_pending;
44 struct work_struct reset_work;
47 static inline u32 ba431_trng_read_reg(struct ba431_trng *ba431, u32 reg)
49 return ioread32(ba431->base + reg);
52 static inline void ba431_trng_write_reg(struct ba431_trng *ba431, u32 reg,
55 iowrite32(val, ba431->base + reg);
58 static inline enum ba431_state ba431_trng_get_state(struct ba431_trng *ba431)
60 u32 status = ba431_trng_read_reg(ba431, BA431_REG_STATUS);
62 return (status & BA431_STATUS_STATE_MASK) >> BA431_STATUS_STATE_OFFSET;
65 static int ba431_trng_is_in_error(struct ba431_trng *ba431)
67 enum ba431_state state = ba431_trng_get_state(ba431);
69 if ((state < BA431_STATE_STARTUP) ||
70 (state >= BA431_STATE_ERROR))
76 static int ba431_trng_reset(struct ba431_trng *ba431)
80 /* Disable interrupts, random generation and enable the softreset */
81 ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_SOFTRESET);
82 udelay(BA431_RESET_DELAY);
83 ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_ENABLE);
85 /* Wait until the state changed */
86 if (readx_poll_timeout(ba431_trng_is_in_error, ba431, ret, !ret,
87 BA431_RESET_READ_STATUS_INTERVAL,
88 BA431_RESET_READ_STATUS_TIMEOUT)) {
89 dev_err(ba431->dev, "reset failed (state: %d)\n",
90 ba431_trng_get_state(ba431));
94 dev_info(ba431->dev, "reset done\n");
99 static void ba431_trng_reset_work(struct work_struct *work)
101 struct ba431_trng *ba431 = container_of(work, struct ba431_trng,
103 ba431_trng_reset(ba431);
104 atomic_set(&ba431->reset_pending, 0);
107 static void ba431_trng_schedule_reset(struct ba431_trng *ba431)
109 if (atomic_cmpxchg(&ba431->reset_pending, 0, 1))
112 schedule_work(&ba431->reset_work);
115 static int ba431_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
117 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
119 unsigned int level, i;
123 level = ba431_trng_read_reg(ba431, BA431_REG_FIFO_LEVEL);
125 if (ba431_trng_is_in_error(ba431)) {
126 ba431_trng_schedule_reset(ba431);
133 udelay(BA431_READ_RETRY_INTERVAL);
139 data[n++] = ba431_trng_read_reg(ba431,
141 max -= sizeof(*data);
142 } while (--i && (max > 0));
144 if (ba431_trng_is_in_error(ba431)) {
146 ba431_trng_schedule_reset(ba431);
152 return (n || !wait) ? n : -EIO;
155 static void ba431_trng_cleanup(struct hwrng *rng)
157 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
159 ba431_trng_write_reg(ba431, BA431_REG_CTRL, 0);
160 cancel_work_sync(&ba431->reset_work);
163 static int ba431_trng_init(struct hwrng *rng)
165 struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
167 return ba431_trng_reset(ba431);
170 static int ba431_trng_probe(struct platform_device *pdev)
172 struct ba431_trng *ba431;
173 struct resource *res;
176 ba431 = devm_kzalloc(&pdev->dev, sizeof(*ba431), GFP_KERNEL);
180 ba431->dev = &pdev->dev;
182 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
183 ba431->base = devm_ioremap_resource(&pdev->dev, res);
184 if (IS_ERR(ba431->base))
185 return PTR_ERR(ba431->base);
187 atomic_set(&ba431->reset_pending, 0);
188 INIT_WORK(&ba431->reset_work, ba431_trng_reset_work);
189 ba431->rng.name = pdev->name;
190 ba431->rng.init = ba431_trng_init;
191 ba431->rng.cleanup = ba431_trng_cleanup;
192 ba431->rng.read = ba431_trng_read;
194 platform_set_drvdata(pdev, ba431);
196 ret = hwrng_register(&ba431->rng);
198 dev_err(&pdev->dev, "BA431 registration failed (%d)\n", ret);
202 dev_info(&pdev->dev, "BA431 TRNG registered\n");
207 static int ba431_trng_remove(struct platform_device *pdev)
209 struct ba431_trng *ba431 = platform_get_drvdata(pdev);
211 hwrng_unregister(&ba431->rng);
216 static const struct of_device_id ba431_trng_dt_ids[] = {
217 { .compatible = "silex-insight,ba431-rng", .data = NULL },
220 MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids);
222 static struct platform_driver ba431_trng_driver = {
225 .of_match_table = ba431_trng_dt_ids,
227 .probe = ba431_trng_probe,
228 .remove = ba431_trng_remove,
231 module_platform_driver(ba431_trng_driver);
233 MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>");
234 MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431");
235 MODULE_LICENSE("GPL");