drivers/char/hw_random/ba431-rng.c

   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/mod_devicetable.h>
  10 #include <linux/module.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/workqueue.h>
  13
  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 */
  18
  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
  23
  24 #define BA431_CTRL_ENABLE                       BIT(0)
  25 #define BA431_CTRL_SOFTRESET                    BIT(8)
  26
  27 #define BA431_STATUS_STATE_MASK                 (BIT(1) | BIT(2) | BIT(3))
  28 #define BA431_STATUS_STATE_OFFSET               1
  29
  30 enum ba431_state {
  31         BA431_STATE_RESET,
  32         BA431_STATE_STARTUP,
  33         BA431_STATE_FIFOFULLON,
  34         BA431_STATE_FIFOFULLOFF,
  35         BA431_STATE_RUNNING,
  36         BA431_STATE_ERROR
  37 };
  38
  39 struct ba431_trng {
  40         struct device *dev;
  41         void __iomem *base;
  42         struct hwrng rng;
  43         atomic_t reset_pending;
  44         struct work_struct reset_work;
  45 };
  46
  47 static inline u32 ba431_trng_read_reg(struct ba431_trng *ba431, u32 reg)
  48 {
  49         return ioread32(ba431->base + reg);
  50 }
  51
  52 static inline void ba431_trng_write_reg(struct ba431_trng *ba431, u32 reg,
  53                                         u32 val)
  54 {
  55         iowrite32(val, ba431->base + reg);
  56 }
  57
  58 static inline enum ba431_state ba431_trng_get_state(struct ba431_trng *ba431)
  59 {
  60         u32 status = ba431_trng_read_reg(ba431, BA431_REG_STATUS);
  61
  62         return (status & BA431_STATUS_STATE_MASK) >> BA431_STATUS_STATE_OFFSET;
  63 }
  64
  65 static int ba431_trng_is_in_error(struct ba431_trng *ba431)
  66 {
  67         enum ba431_state state = ba431_trng_get_state(ba431);
  68
  69         if ((state < BA431_STATE_STARTUP) ||
  70             (state >= BA431_STATE_ERROR))
  71                 return 1;
  72
  73         return 0;
  74 }
  75
  76 static int ba431_trng_reset(struct ba431_trng *ba431)
  77 {
  78         int ret;
  79
  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);
  84
  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));
  91                 return -ETIMEDOUT;
  92         }
  93
  94         dev_info(ba431->dev, "reset done\n");
  95
  96         return 0;
  97 }
  98
  99 static void ba431_trng_reset_work(struct work_struct *work)
 100 {
 101         struct ba431_trng *ba431 = container_of(work, struct ba431_trng,
 102                                                 reset_work);
 103         ba431_trng_reset(ba431);
 104         atomic_set(&ba431->reset_pending, 0);
 105 }
 106
 107 static void ba431_trng_schedule_reset(struct ba431_trng *ba431)
 108 {
 109         if (atomic_cmpxchg(&ba431->reset_pending, 0, 1))
 110                 return;
 111
 112         schedule_work(&ba431->reset_work);
 113 }
 114
 115 static int ba431_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
 116 {
 117         struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
 118         u32 *data = buf;
 119         unsigned int level, i;
 120         int n = 0;
 121
 122         while (max > 0) {
 123                 level = ba431_trng_read_reg(ba431, BA431_REG_FIFO_LEVEL);
 124                 if (!level) {
 125                         if (ba431_trng_is_in_error(ba431)) {
 126                                 ba431_trng_schedule_reset(ba431);
 127                                 break;
 128                         }
 129
 130                         if (!wait)
 131                                 break;
 132
 133                         udelay(BA431_READ_RETRY_INTERVAL);
 134                         continue;
 135                 }
 136
 137                 i = level;
 138                 do {
 139                         data[n++] = ba431_trng_read_reg(ba431,
 140                                                         BA431_REG_FIFODATA);
 141                         max -= sizeof(*data);
 142                 } while (--i && (max > 0));
 143
 144                 if (ba431_trng_is_in_error(ba431)) {
 145                         n -= (level - i);
 146                         ba431_trng_schedule_reset(ba431);
 147                         break;
 148                 }
 149         }
 150
 151         n *= sizeof(data);
 152         return (n || !wait) ? n : -EIO;
 153 }
 154
 155 static void ba431_trng_cleanup(struct hwrng *rng)
 156 {
 157         struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
 158
 159         ba431_trng_write_reg(ba431, BA431_REG_CTRL, 0);
 160         cancel_work_sync(&ba431->reset_work);
 161 }
 162
 163 static int ba431_trng_init(struct hwrng *rng)
 164 {
 165         struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
 166
 167         return ba431_trng_reset(ba431);
 168 }
 169
 170 static int ba431_trng_probe(struct platform_device *pdev)
 171 {
 172         struct ba431_trng *ba431;
 173         int ret;
 174
 175         ba431 = devm_kzalloc(&pdev->dev, sizeof(*ba431), GFP_KERNEL);
 176         if (!ba431)
 177                 return -ENOMEM;
 178
 179         ba431->dev = &pdev->dev;
 180
 181         ba431->base = devm_platform_ioremap_resource(pdev, 0);
 182         if (IS_ERR(ba431->base))
 183                 return PTR_ERR(ba431->base);
 184
 185         atomic_set(&ba431->reset_pending, 0);
 186         INIT_WORK(&ba431->reset_work, ba431_trng_reset_work);
 187         ba431->rng.name = pdev->name;
 188         ba431->rng.init = ba431_trng_init;
 189         ba431->rng.cleanup = ba431_trng_cleanup;
 190         ba431->rng.read = ba431_trng_read;
 191
 192         platform_set_drvdata(pdev, ba431);
 193
 194         ret = devm_hwrng_register(&pdev->dev, &ba431->rng);
 195         if (ret) {
 196                 dev_err(&pdev->dev, "BA431 registration failed (%d)\n", ret);
 197                 return ret;
 198         }
 199
 200         dev_info(&pdev->dev, "BA431 TRNG registered\n");
 201
 202         return 0;
 203 }
 204
 205 static const struct of_device_id ba431_trng_dt_ids[] = {
 206         { .compatible = "silex-insight,ba431-rng", .data = NULL },
 207         { /* sentinel */ }
 208 };
 209 MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids);
 210
 211 static struct platform_driver ba431_trng_driver = {
 212         .driver = {
 213                 .name = "ba431-rng",
 214                 .of_match_table = ba431_trng_dt_ids,
 215         },
 216         .probe = ba431_trng_probe,
 217 };
 218
 219 module_platform_driver(ba431_trng_driver);
 220
 221 MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>");
 222 MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431");
 223 MODULE_LICENSE("GPL");