1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (c) 2015, Daniel Thompson 4 */ 5 6 #include <linux/clk.h> 7 #include <linux/delay.h> 8 #include <linux/hw_random.h> 9 #include <linux/io.h> 10 #include <linux/iopoll.h> 11 #include <linux/kernel.h> 12 #include <linux/module.h> 13 #include <linux/of.h> 14 #include <linux/of_address.h> 15 #include <linux/platform_device.h> 16 #include <linux/pm_runtime.h> 17 #include <linux/reset.h> 18 #include <linux/slab.h> 19 20 #define RNG_CR 0x00 21 #define RNG_CR_RNGEN BIT(2) 22 #define RNG_CR_CED BIT(5) 23 #define RNG_CR_CONFIG1 GENMASK(11, 8) 24 #define RNG_CR_NISTC BIT(12) 25 #define RNG_CR_CONFIG2 GENMASK(15, 13) 26 #define RNG_CR_CLKDIV_SHIFT 16 27 #define RNG_CR_CLKDIV GENMASK(19, 16) 28 #define RNG_CR_CONFIG3 GENMASK(25, 20) 29 #define RNG_CR_CONDRST BIT(30) 30 #define RNG_CR_CONFLOCK BIT(31) 31 #define RNG_CR_ENTROPY_SRC_MASK (RNG_CR_CONFIG1 | RNG_CR_NISTC | RNG_CR_CONFIG2 | RNG_CR_CONFIG3) 32 #define RNG_CR_CONFIG_MASK (RNG_CR_ENTROPY_SRC_MASK | RNG_CR_CED | RNG_CR_CLKDIV) 33 34 #define RNG_SR 0x04 35 #define RNG_SR_DRDY BIT(0) 36 #define RNG_SR_CECS BIT(1) 37 #define RNG_SR_SECS BIT(2) 38 #define RNG_SR_CEIS BIT(5) 39 #define RNG_SR_SEIS BIT(6) 40 41 #define RNG_DR 0x08 42 43 #define RNG_NSCR 0x0C 44 #define RNG_NSCR_MASK GENMASK(17, 0) 45 46 #define RNG_HTCR 0x10 47 48 #define RNG_NB_RECOVER_TRIES 3 49 50 struct stm32_rng_data { 51 uint max_clock_rate; 52 u32 cr; 53 u32 nscr; 54 u32 htcr; 55 bool has_cond_reset; 56 }; 57 58 /** 59 * struct stm32_rng_config - RNG configuration data 60 * 61 * @cr: RNG configuration. 0 means default hardware RNG configuration 62 * @nscr: Noise sources control configuration. 63 * @htcr: Health tests configuration. 64 */ 65 struct stm32_rng_config { 66 u32 cr; 67 u32 nscr; 68 u32 htcr; 69 }; 70 71 struct stm32_rng_private { 72 struct hwrng rng; 73 struct device *dev; 74 void __iomem *base; 75 struct clk *clk; 76 struct reset_control *rst; 77 struct stm32_rng_config pm_conf; 78 const struct stm32_rng_data *data; 79 bool ced; 80 bool lock_conf; 81 }; 82 83 /* 84 * Extracts from the STM32 RNG specification when RNG supports CONDRST. 85 * 86 * When a noise source (or seed) error occurs, the RNG stops generating 87 * random numbers and sets to “1” both SEIS and SECS bits to indicate 88 * that a seed error occurred. (...) 89 * 90 * 1. Software reset by writing CONDRST at 1 and at 0 (see bitfield 91 * description for details). This step is needed only if SECS is set. 92 * Indeed, when SEIS is set and SECS is cleared it means RNG performed 93 * the reset automatically (auto-reset). 94 * 2. If SECS was set in step 1 (no auto-reset) wait for CONDRST 95 * to be cleared in the RNG_CR register, then confirm that SEIS is 96 * cleared in the RNG_SR register. Otherwise just clear SEIS bit in 97 * the RNG_SR register. 98 * 3. If SECS was set in step 1 (no auto-reset) wait for SECS to be 99 * cleared by RNG. The random number generation is now back to normal. 100 */ 101 static int stm32_rng_conceal_seed_error_cond_reset(struct stm32_rng_private *priv) 102 { 103 struct device *dev = priv->dev; 104 u32 sr = readl_relaxed(priv->base + RNG_SR); 105 u32 cr = readl_relaxed(priv->base + RNG_CR); 106 int err; 107 108 if (sr & RNG_SR_SECS) { 109 /* Conceal by resetting the subsystem (step 1.) */ 110 writel_relaxed(cr | RNG_CR_CONDRST, priv->base + RNG_CR); 111 writel_relaxed(cr & ~RNG_CR_CONDRST, priv->base + RNG_CR); 112 } else { 113 /* RNG auto-reset (step 2.) */ 114 writel_relaxed(sr & ~RNG_SR_SEIS, priv->base + RNG_SR); 115 goto end; 116 } 117 118 err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_CR, cr, !(cr & RNG_CR_CONDRST), 10, 119 100000); 120 if (err) { 121 dev_err(dev, "%s: timeout %x\n", __func__, sr); 122 return err; 123 } 124 125 /* Check SEIS is cleared (step 2.) */ 126 if (readl_relaxed(priv->base + RNG_SR) & RNG_SR_SEIS) 127 return -EINVAL; 128 129 err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_SR, sr, !(sr & RNG_SR_SECS), 10, 130 100000); 131 if (err) { 132 dev_err(dev, "%s: timeout %x\n", __func__, sr); 133 return err; 134 } 135 136 end: 137 return 0; 138 } 139 140 /* 141 * Extracts from the STM32 RNG specification, when CONDRST is not supported 142 * 143 * When a noise source (or seed) error occurs, the RNG stops generating 144 * random numbers and sets to “1” both SEIS and SECS bits to indicate 145 * that a seed error occurred. (...) 146 * 147 * The following sequence shall be used to fully recover from a seed 148 * error after the RNG initialization: 149 * 1. Clear the SEIS bit by writing it to “0”. 150 * 2. Read out 12 words from the RNG_DR register, and discard each of 151 * them in order to clean the pipeline. 152 * 3. Confirm that SEIS is still cleared. Random number generation is 153 * back to normal. 154 */ 155 static int stm32_rng_conceal_seed_error_sw_reset(struct stm32_rng_private *priv) 156 { 157 unsigned int i = 0; 158 u32 sr = readl_relaxed(priv->base + RNG_SR); 159 160 writel_relaxed(sr & ~RNG_SR_SEIS, priv->base + RNG_SR); 161 162 for (i = 12; i != 0; i--) 163 (void)readl_relaxed(priv->base + RNG_DR); 164 165 if (readl_relaxed(priv->base + RNG_SR) & RNG_SR_SEIS) 166 return -EINVAL; 167 168 return 0; 169 } 170 171 static int stm32_rng_conceal_seed_error(struct hwrng *rng) 172 { 173 struct stm32_rng_private *priv = container_of(rng, struct stm32_rng_private, rng); 174 175 dev_dbg(priv->dev, "Concealing seed error\n"); 176 177 if (priv->data->has_cond_reset) 178 return stm32_rng_conceal_seed_error_cond_reset(priv); 179 else 180 return stm32_rng_conceal_seed_error_sw_reset(priv); 181 }; 182 183 184 static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 185 { 186 struct stm32_rng_private *priv = container_of(rng, struct stm32_rng_private, rng); 187 unsigned int i = 0; 188 int retval = 0, err = 0; 189 u32 sr; 190 191 retval = pm_runtime_resume_and_get(priv->dev); 192 if (retval) 193 return retval; 194 195 if (readl_relaxed(priv->base + RNG_SR) & RNG_SR_SEIS) 196 stm32_rng_conceal_seed_error(rng); 197 198 while (max >= sizeof(u32)) { 199 sr = readl_relaxed(priv->base + RNG_SR); 200 /* 201 * Manage timeout which is based on timer and take 202 * care of initial delay time when enabling the RNG. 203 */ 204 if (!sr && wait) { 205 err = readl_relaxed_poll_timeout_atomic(priv->base 206 + RNG_SR, 207 sr, sr, 208 10, 50000); 209 if (err) { 210 dev_err(priv->dev, "%s: timeout %x!\n", __func__, sr); 211 break; 212 } 213 } else if (!sr) { 214 /* The FIFO is being filled up */ 215 break; 216 } 217 218 if (sr != RNG_SR_DRDY) { 219 if (sr & RNG_SR_SEIS) { 220 err = stm32_rng_conceal_seed_error(rng); 221 i++; 222 if (err && i > RNG_NB_RECOVER_TRIES) { 223 dev_err(priv->dev, "Couldn't recover from seed error\n"); 224 retval = -ENOTRECOVERABLE; 225 goto exit_rpm; 226 } 227 228 continue; 229 } 230 231 if (WARN_ONCE((sr & RNG_SR_CEIS), "RNG clock too slow - %x\n", sr)) 232 writel_relaxed(0, priv->base + RNG_SR); 233 } 234 235 /* Late seed error case: DR being 0 is an error status */ 236 *(u32 *)data = readl_relaxed(priv->base + RNG_DR); 237 if (!*(u32 *)data) { 238 err = stm32_rng_conceal_seed_error(rng); 239 i++; 240 if (err && i > RNG_NB_RECOVER_TRIES) { 241 dev_err(priv->dev, "Couldn't recover from seed error"); 242 retval = -ENOTRECOVERABLE; 243 goto exit_rpm; 244 } 245 246 continue; 247 } 248 249 i = 0; 250 retval += sizeof(u32); 251 data += sizeof(u32); 252 max -= sizeof(u32); 253 } 254 255 exit_rpm: 256 pm_runtime_mark_last_busy(priv->dev); 257 pm_runtime_put_sync_autosuspend(priv->dev); 258 259 return retval || !wait ? retval : -EIO; 260 } 261 262 static uint stm32_rng_clock_freq_restrain(struct hwrng *rng) 263 { 264 struct stm32_rng_private *priv = 265 container_of(rng, struct stm32_rng_private, rng); 266 unsigned long clock_rate = 0; 267 uint clock_div = 0; 268 269 clock_rate = clk_get_rate(priv->clk); 270 271 /* 272 * Get the exponent to apply on the CLKDIV field in RNG_CR register 273 * No need to handle the case when clock-div > 0xF as it is physically 274 * impossible 275 */ 276 while ((clock_rate >> clock_div) > priv->data->max_clock_rate) 277 clock_div++; 278 279 pr_debug("RNG clk rate : %lu\n", clk_get_rate(priv->clk) >> clock_div); 280 281 return clock_div; 282 } 283 284 static int stm32_rng_init(struct hwrng *rng) 285 { 286 struct stm32_rng_private *priv = 287 container_of(rng, struct stm32_rng_private, rng); 288 int err; 289 u32 reg; 290 291 err = clk_prepare_enable(priv->clk); 292 if (err) 293 return err; 294 295 /* clear error indicators */ 296 writel_relaxed(0, priv->base + RNG_SR); 297 298 reg = readl_relaxed(priv->base + RNG_CR); 299 300 /* 301 * Keep default RNG configuration if none was specified. 302 * 0 is an invalid value as it disables all entropy sources. 303 */ 304 if (priv->data->has_cond_reset && priv->data->cr) { 305 uint clock_div = stm32_rng_clock_freq_restrain(rng); 306 307 reg &= ~RNG_CR_CONFIG_MASK; 308 reg |= RNG_CR_CONDRST | (priv->data->cr & RNG_CR_ENTROPY_SRC_MASK) | 309 (clock_div << RNG_CR_CLKDIV_SHIFT); 310 if (priv->ced) 311 reg &= ~RNG_CR_CED; 312 else 313 reg |= RNG_CR_CED; 314 writel_relaxed(reg, priv->base + RNG_CR); 315 316 /* Health tests and noise control registers */ 317 writel_relaxed(priv->data->htcr, priv->base + RNG_HTCR); 318 writel_relaxed(priv->data->nscr & RNG_NSCR_MASK, priv->base + RNG_NSCR); 319 320 reg &= ~RNG_CR_CONDRST; 321 reg |= RNG_CR_RNGEN; 322 if (priv->lock_conf) 323 reg |= RNG_CR_CONFLOCK; 324 325 writel_relaxed(reg, priv->base + RNG_CR); 326 327 err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_CR, reg, 328 (!(reg & RNG_CR_CONDRST)), 329 10, 50000); 330 if (err) { 331 clk_disable_unprepare(priv->clk); 332 dev_err(priv->dev, "%s: timeout %x!\n", __func__, reg); 333 return -EINVAL; 334 } 335 } else { 336 /* Handle all RNG versions by checking if conditional reset should be set */ 337 if (priv->data->has_cond_reset) 338 reg |= RNG_CR_CONDRST; 339 340 if (priv->ced) 341 reg &= ~RNG_CR_CED; 342 else 343 reg |= RNG_CR_CED; 344 345 writel_relaxed(reg, priv->base + RNG_CR); 346 347 if (priv->data->has_cond_reset) 348 reg &= ~RNG_CR_CONDRST; 349 350 reg |= RNG_CR_RNGEN; 351 352 writel_relaxed(reg, priv->base + RNG_CR); 353 } 354 355 err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_SR, reg, 356 reg & RNG_SR_DRDY, 357 10, 100000); 358 if (err || (reg & ~RNG_SR_DRDY)) { 359 clk_disable_unprepare(priv->clk); 360 dev_err(priv->dev, "%s: timeout:%x SR: %x!\n", __func__, err, reg); 361 return -EINVAL; 362 } 363 364 clk_disable_unprepare(priv->clk); 365 366 return 0; 367 } 368 369 static void stm32_rng_remove(struct platform_device *ofdev) 370 { 371 pm_runtime_disable(&ofdev->dev); 372 } 373 374 static int __maybe_unused stm32_rng_runtime_suspend(struct device *dev) 375 { 376 struct stm32_rng_private *priv = dev_get_drvdata(dev); 377 u32 reg; 378 379 reg = readl_relaxed(priv->base + RNG_CR); 380 reg &= ~RNG_CR_RNGEN; 381 writel_relaxed(reg, priv->base + RNG_CR); 382 clk_disable_unprepare(priv->clk); 383 384 return 0; 385 } 386 387 static int __maybe_unused stm32_rng_suspend(struct device *dev) 388 { 389 struct stm32_rng_private *priv = dev_get_drvdata(dev); 390 int err; 391 392 err = clk_prepare_enable(priv->clk); 393 if (err) 394 return err; 395 396 if (priv->data->has_cond_reset) { 397 priv->pm_conf.nscr = readl_relaxed(priv->base + RNG_NSCR); 398 priv->pm_conf.htcr = readl_relaxed(priv->base + RNG_HTCR); 399 } 400 401 /* Do not save that RNG is enabled as it will be handled at resume */ 402 priv->pm_conf.cr = readl_relaxed(priv->base + RNG_CR) & ~RNG_CR_RNGEN; 403 404 writel_relaxed(priv->pm_conf.cr, priv->base + RNG_CR); 405 406 clk_disable_unprepare(priv->clk); 407 408 return 0; 409 } 410 411 static int __maybe_unused stm32_rng_runtime_resume(struct device *dev) 412 { 413 struct stm32_rng_private *priv = dev_get_drvdata(dev); 414 int err; 415 u32 reg; 416 417 err = clk_prepare_enable(priv->clk); 418 if (err) 419 return err; 420 421 /* Clean error indications */ 422 writel_relaxed(0, priv->base + RNG_SR); 423 424 reg = readl_relaxed(priv->base + RNG_CR); 425 reg |= RNG_CR_RNGEN; 426 writel_relaxed(reg, priv->base + RNG_CR); 427 428 return 0; 429 } 430 431 static int __maybe_unused stm32_rng_resume(struct device *dev) 432 { 433 struct stm32_rng_private *priv = dev_get_drvdata(dev); 434 int err; 435 u32 reg; 436 437 err = clk_prepare_enable(priv->clk); 438 if (err) 439 return err; 440 441 /* Clean error indications */ 442 writel_relaxed(0, priv->base + RNG_SR); 443 444 if (priv->data->has_cond_reset) { 445 /* 446 * Correct configuration in bits [29:4] must be set in the same 447 * access that set RNG_CR_CONDRST bit. Else config setting is 448 * not taken into account. CONFIGLOCK bit must also be unset but 449 * it is not handled at the moment. 450 */ 451 writel_relaxed(priv->pm_conf.cr | RNG_CR_CONDRST, priv->base + RNG_CR); 452 453 writel_relaxed(priv->pm_conf.nscr, priv->base + RNG_NSCR); 454 writel_relaxed(priv->pm_conf.htcr, priv->base + RNG_HTCR); 455 456 reg = readl_relaxed(priv->base + RNG_CR); 457 reg |= RNG_CR_RNGEN; 458 reg &= ~RNG_CR_CONDRST; 459 writel_relaxed(reg, priv->base + RNG_CR); 460 461 err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_CR, reg, 462 reg & ~RNG_CR_CONDRST, 10, 100000); 463 464 if (err) { 465 clk_disable_unprepare(priv->clk); 466 dev_err(priv->dev, "%s: timeout:%x CR: %x!\n", __func__, err, reg); 467 return -EINVAL; 468 } 469 } else { 470 reg = priv->pm_conf.cr; 471 reg |= RNG_CR_RNGEN; 472 writel_relaxed(reg, priv->base + RNG_CR); 473 } 474 475 clk_disable_unprepare(priv->clk); 476 477 return 0; 478 } 479 480 static const struct dev_pm_ops __maybe_unused stm32_rng_pm_ops = { 481 SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend, 482 stm32_rng_runtime_resume, NULL) 483 SET_SYSTEM_SLEEP_PM_OPS(stm32_rng_suspend, 484 stm32_rng_resume) 485 }; 486 487 static const struct stm32_rng_data stm32mp13_rng_data = { 488 .has_cond_reset = true, 489 .max_clock_rate = 48000000, 490 .cr = 0x00F00D00, 491 .nscr = 0x2B5BB, 492 .htcr = 0x969D, 493 }; 494 495 static const struct stm32_rng_data stm32_rng_data = { 496 .has_cond_reset = false, 497 .max_clock_rate = 3000000, 498 }; 499 500 static const struct of_device_id stm32_rng_match[] = { 501 { 502 .compatible = "st,stm32mp13-rng", 503 .data = &stm32mp13_rng_data, 504 }, 505 { 506 .compatible = "st,stm32-rng", 507 .data = &stm32_rng_data, 508 }, 509 {}, 510 }; 511 MODULE_DEVICE_TABLE(of, stm32_rng_match); 512 513 static int stm32_rng_probe(struct platform_device *ofdev) 514 { 515 struct device *dev = &ofdev->dev; 516 struct device_node *np = ofdev->dev.of_node; 517 struct stm32_rng_private *priv; 518 struct resource *res; 519 520 priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL); 521 if (!priv) 522 return -ENOMEM; 523 524 priv->base = devm_platform_get_and_ioremap_resource(ofdev, 0, &res); 525 if (IS_ERR(priv->base)) 526 return PTR_ERR(priv->base); 527 528 priv->clk = devm_clk_get(&ofdev->dev, NULL); 529 if (IS_ERR(priv->clk)) 530 return PTR_ERR(priv->clk); 531 532 priv->rst = devm_reset_control_get(&ofdev->dev, NULL); 533 if (!IS_ERR(priv->rst)) { 534 reset_control_assert(priv->rst); 535 udelay(2); 536 reset_control_deassert(priv->rst); 537 } 538 539 priv->ced = of_property_read_bool(np, "clock-error-detect"); 540 priv->lock_conf = of_property_read_bool(np, "st,rng-lock-conf"); 541 priv->dev = dev; 542 543 priv->data = of_device_get_match_data(dev); 544 if (!priv->data) 545 return -ENODEV; 546 547 dev_set_drvdata(dev, priv); 548 549 priv->rng.name = dev_driver_string(dev); 550 priv->rng.init = stm32_rng_init; 551 priv->rng.read = stm32_rng_read; 552 priv->rng.quality = 900; 553 554 pm_runtime_set_autosuspend_delay(dev, 100); 555 pm_runtime_use_autosuspend(dev); 556 pm_runtime_enable(dev); 557 558 return devm_hwrng_register(dev, &priv->rng); 559 } 560 561 static struct platform_driver stm32_rng_driver = { 562 .driver = { 563 .name = "stm32-rng", 564 .pm = pm_ptr(&stm32_rng_pm_ops), 565 .of_match_table = stm32_rng_match, 566 }, 567 .probe = stm32_rng_probe, 568 .remove_new = stm32_rng_remove, 569 }; 570 571 module_platform_driver(stm32_rng_driver); 572 573 MODULE_LICENSE("GPL"); 574 MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>"); 575 MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver"); 576