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 ret = devm_hwrng_register(&pdev->dev, &ba431->rng); 193 if (ret) 194 return dev_err_probe(&pdev->dev, ret, "BA431 registration failed\n"); 195 196 dev_info(&pdev->dev, "BA431 TRNG registered\n"); 197 198 return 0; 199 } 200 201 static const struct of_device_id ba431_trng_dt_ids[] = { 202 { .compatible = "silex-insight,ba431-rng" }, 203 { /* sentinel */ } 204 }; 205 MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids); 206 207 static struct platform_driver ba431_trng_driver = { 208 .driver = { 209 .name = "ba431-rng", 210 .of_match_table = ba431_trng_dt_ids, 211 }, 212 .probe = ba431_trng_probe, 213 }; 214 215 module_platform_driver(ba431_trng_driver); 216 217 MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>"); 218 MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431"); 219 MODULE_LICENSE("GPL"); 220