drivers/char/hw_random/imx-rngc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * RNG driver for Freescale RNGC
   4  *
   5  * Copyright (C) 2008-2012 Freescale Semiconductor, Inc.
   6  * Copyright (C) 2017 Martin Kaiser <martin@kaiser.cx>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/mod_devicetable.h>
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/clk.h>
  14 #include <linux/err.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/hw_random.h>
  18 #include <linux/completion.h>
  19 #include <linux/io.h>
  20
  21 #define RNGC_VER_ID                     0x0000
  22 #define RNGC_COMMAND                    0x0004
  23 #define RNGC_CONTROL                    0x0008
  24 #define RNGC_STATUS                     0x000C
  25 #define RNGC_ERROR                      0x0010
  26 #define RNGC_FIFO                       0x0014
  27
  28 /* the fields in the ver id register */
  29 #define RNGC_TYPE_SHIFT         28
  30 #define RNGC_VER_MAJ_SHIFT              8
  31
  32 /* the rng_type field */
  33 #define RNGC_TYPE_RNGB                  0x1
  34 #define RNGC_TYPE_RNGC                  0x2
  35
  36
  37 #define RNGC_CMD_CLR_ERR                0x00000020
  38 #define RNGC_CMD_CLR_INT                0x00000010
  39 #define RNGC_CMD_SEED                   0x00000002
  40 #define RNGC_CMD_SELF_TEST              0x00000001
  41
  42 #define RNGC_CTRL_MASK_ERROR            0x00000040
  43 #define RNGC_CTRL_MASK_DONE             0x00000020
  44 #define RNGC_CTRL_AUTO_SEED             0x00000010
  45
  46 #define RNGC_STATUS_ERROR               0x00010000
  47 #define RNGC_STATUS_FIFO_LEVEL_MASK     0x00000f00
  48 #define RNGC_STATUS_FIFO_LEVEL_SHIFT    8
  49 #define RNGC_STATUS_SEED_DONE           0x00000020
  50 #define RNGC_STATUS_ST_DONE             0x00000010
  51
  52 #define RNGC_ERROR_STATUS_STAT_ERR      0x00000008
  53
  54 #define RNGC_TIMEOUT  3000 /* 3 sec */
  55
  56
  57 static bool self_test = true;
  58 module_param(self_test, bool, 0);
  59
  60 struct imx_rngc {
  61         struct device           *dev;
  62         struct clk              *clk;
  63         void __iomem            *base;
  64         struct hwrng            rng;
  65         struct completion       rng_op_done;
  66         /*
  67          * err_reg is written only by the irq handler and read only
  68          * when interrupts are masked, we need no spinlock
  69          */
  70         u32                     err_reg;
  71 };
  72
  73
  74 static inline void imx_rngc_irq_mask_clear(struct imx_rngc *rngc)
  75 {
  76         u32 ctrl, cmd;
  77
  78         /* mask interrupts */
  79         ctrl = readl(rngc->base + RNGC_CONTROL);
  80         ctrl |= RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR;
  81         writel(ctrl, rngc->base + RNGC_CONTROL);
  82
  83         /*
  84          * CLR_INT clears the interrupt only if there's no error
  85          * CLR_ERR clear the interrupt and the error register if there
  86          * is an error
  87          */
  88         cmd = readl(rngc->base + RNGC_COMMAND);
  89         cmd |= RNGC_CMD_CLR_INT | RNGC_CMD_CLR_ERR;
  90         writel(cmd, rngc->base + RNGC_COMMAND);
  91 }
  92
  93 static inline void imx_rngc_irq_unmask(struct imx_rngc *rngc)
  94 {
  95         u32 ctrl;
  96
  97         ctrl = readl(rngc->base + RNGC_CONTROL);
  98         ctrl &= ~(RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR);
  99         writel(ctrl, rngc->base + RNGC_CONTROL);
 100 }
 101
 102 static int imx_rngc_self_test(struct imx_rngc *rngc)
 103 {
 104         u32 cmd;
 105         int ret;
 106
 107         imx_rngc_irq_unmask(rngc);
 108
 109         /* run self test */
 110         cmd = readl(rngc->base + RNGC_COMMAND);
 111         writel(cmd | RNGC_CMD_SELF_TEST, rngc->base + RNGC_COMMAND);
 112
 113         ret = wait_for_completion_timeout(&rngc->rng_op_done, RNGC_TIMEOUT);
 114         imx_rngc_irq_mask_clear(rngc);
 115         if (!ret)
 116                 return -ETIMEDOUT;
 117
 118         return rngc->err_reg ? -EIO : 0;
 119 }
 120
 121 static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool wait)
 122 {
 123         struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
 124         unsigned int status;
 125         unsigned int level;
 126         int retval = 0;
 127
 128         while (max >= sizeof(u32)) {
 129                 status = readl(rngc->base + RNGC_STATUS);
 130
 131                 /* is there some error while reading this random number? */
 132                 if (status & RNGC_STATUS_ERROR)
 133                         break;
 134
 135                 /* how many random numbers are in FIFO? [0-16] */
 136                 level = (status & RNGC_STATUS_FIFO_LEVEL_MASK) >>
 137                         RNGC_STATUS_FIFO_LEVEL_SHIFT;
 138
 139                 if (level) {
 140                         /* retrieve a random number from FIFO */
 141                         *(u32 *)data = readl(rngc->base + RNGC_FIFO);
 142
 143                         retval += sizeof(u32);
 144                         data += sizeof(u32);
 145                         max -= sizeof(u32);
 146                 }
 147         }
 148
 149         return retval ? retval : -EIO;
 150 }
 151
 152 static irqreturn_t imx_rngc_irq(int irq, void *priv)
 153 {
 154         struct imx_rngc *rngc = (struct imx_rngc *)priv;
 155         u32 status;
 156
 157         /*
 158          * clearing the interrupt will also clear the error register
 159          * read error and status before clearing
 160          */
 161         status = readl(rngc->base + RNGC_STATUS);
 162         rngc->err_reg = readl(rngc->base + RNGC_ERROR);
 163
 164         imx_rngc_irq_mask_clear(rngc);
 165
 166         if (status & (RNGC_STATUS_SEED_DONE | RNGC_STATUS_ST_DONE))
 167                 complete(&rngc->rng_op_done);
 168
 169         return IRQ_HANDLED;
 170 }
 171
 172 static int imx_rngc_init(struct hwrng *rng)
 173 {
 174         struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
 175         u32 cmd, ctrl;
 176         int ret;
 177
 178         /* clear error */
 179         cmd = readl(rngc->base + RNGC_COMMAND);
 180         writel(cmd | RNGC_CMD_CLR_ERR, rngc->base + RNGC_COMMAND);
 181
 182         imx_rngc_irq_unmask(rngc);
 183
 184         /* create seed, repeat while there is some statistical error */
 185         do {
 186                 /* seed creation */
 187                 cmd = readl(rngc->base + RNGC_COMMAND);
 188                 writel(cmd | RNGC_CMD_SEED, rngc->base + RNGC_COMMAND);
 189
 190                 ret = wait_for_completion_timeout(&rngc->rng_op_done,
 191                                 RNGC_TIMEOUT);
 192
 193                 if (!ret) {
 194                         ret = -ETIMEDOUT;
 195                         goto err;
 196                 }
 197
 198         } while (rngc->err_reg == RNGC_ERROR_STATUS_STAT_ERR);
 199
 200         if (rngc->err_reg) {
 201                 ret = -EIO;
 202                 goto err;
 203         }
 204
 205         /*
 206          * enable automatic seeding, the rngc creates a new seed automatically
 207          * after serving 2^20 random 160-bit words
 208          */
 209         ctrl = readl(rngc->base + RNGC_CONTROL);
 210         ctrl |= RNGC_CTRL_AUTO_SEED;
 211         writel(ctrl, rngc->base + RNGC_CONTROL);
 212
 213         /*
 214          * if initialisation was successful, we keep the interrupt
 215          * unmasked until imx_rngc_cleanup is called
 216          * we mask the interrupt ourselves if we return an error
 217          */
 218         return 0;
 219
 220 err:
 221         imx_rngc_irq_mask_clear(rngc);
 222         return ret;
 223 }
 224
 225 static void imx_rngc_cleanup(struct hwrng *rng)
 226 {
 227         struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
 228
 229         imx_rngc_irq_mask_clear(rngc);
 230 }
 231
 232 static int imx_rngc_probe(struct platform_device *pdev)
 233 {
 234         struct imx_rngc *rngc;
 235         int ret;
 236         int irq;
 237         u32 ver_id;
 238         u8  rng_type;
 239
 240         rngc = devm_kzalloc(&pdev->dev, sizeof(*rngc), GFP_KERNEL);
 241         if (!rngc)
 242                 return -ENOMEM;
 243
 244         rngc->base = devm_platform_ioremap_resource(pdev, 0);
 245         if (IS_ERR(rngc->base))
 246                 return PTR_ERR(rngc->base);
 247
 248         rngc->clk = devm_clk_get(&pdev->dev, NULL);
 249         if (IS_ERR(rngc->clk)) {
 250                 dev_err(&pdev->dev, "Can not get rng_clk\n");
 251                 return PTR_ERR(rngc->clk);
 252         }
 253
 254         irq = platform_get_irq(pdev, 0);
 255         if (irq < 0)
 256                 return irq;
 257
 258         ret = clk_prepare_enable(rngc->clk);
 259         if (ret)
 260                 return ret;
 261
 262         ver_id = readl(rngc->base + RNGC_VER_ID);
 263         rng_type = ver_id >> RNGC_TYPE_SHIFT;
 264         /*
 265          * This driver supports only RNGC and RNGB. (There's a different
 266          * driver for RNGA.)
 267          */
 268         if (rng_type != RNGC_TYPE_RNGC && rng_type != RNGC_TYPE_RNGB) {
 269                 ret = -ENODEV;
 270                 goto err;
 271         }
 272
 273         ret = devm_request_irq(&pdev->dev,
 274                         irq, imx_rngc_irq, 0, pdev->name, (void *)rngc);
 275         if (ret) {
 276                 dev_err(rngc->dev, "Can't get interrupt working.\n");
 277                 goto err;
 278         }
 279
 280         init_completion(&rngc->rng_op_done);
 281
 282         rngc->rng.name = pdev->name;
 283         rngc->rng.init = imx_rngc_init;
 284         rngc->rng.read = imx_rngc_read;
 285         rngc->rng.cleanup = imx_rngc_cleanup;
 286         rngc->rng.quality = 19;
 287
 288         rngc->dev = &pdev->dev;
 289         platform_set_drvdata(pdev, rngc);
 290
 291         imx_rngc_irq_mask_clear(rngc);
 292
 293         if (self_test) {
 294                 ret = imx_rngc_self_test(rngc);
 295                 if (ret) {
 296                         dev_err(rngc->dev, "self test failed\n");
 297                         goto err;
 298                 }
 299         }
 300
 301         ret = hwrng_register(&rngc->rng);
 302         if (ret) {
 303                 dev_err(&pdev->dev, "hwrng registration failed\n");
 304                 goto err;
 305         }
 306
 307         dev_info(&pdev->dev,
 308                 "Freescale RNG%c registered (HW revision %d.%02d)\n",
 309                 rng_type == RNGC_TYPE_RNGB ? 'B' : 'C',
 310                 (ver_id >> RNGC_VER_MAJ_SHIFT) & 0xff, ver_id & 0xff);
 311         return 0;
 312
 313 err:
 314         clk_disable_unprepare(rngc->clk);
 315
 316         return ret;
 317 }
 318
 319 static int __exit imx_rngc_remove(struct platform_device *pdev)
 320 {
 321         struct imx_rngc *rngc = platform_get_drvdata(pdev);
 322
 323         hwrng_unregister(&rngc->rng);
 324
 325         clk_disable_unprepare(rngc->clk);
 326
 327         return 0;
 328 }
 329
 330 static int __maybe_unused imx_rngc_suspend(struct device *dev)
 331 {
 332         struct imx_rngc *rngc = dev_get_drvdata(dev);
 333
 334         clk_disable_unprepare(rngc->clk);
 335
 336         return 0;
 337 }
 338
 339 static int __maybe_unused imx_rngc_resume(struct device *dev)
 340 {
 341         struct imx_rngc *rngc = dev_get_drvdata(dev);
 342
 343         clk_prepare_enable(rngc->clk);
 344
 345         return 0;
 346 }
 347
 348 static SIMPLE_DEV_PM_OPS(imx_rngc_pm_ops, imx_rngc_suspend, imx_rngc_resume);
 349
 350 static const struct of_device_id imx_rngc_dt_ids[] = {
 351         { .compatible = "fsl,imx25-rngb", .data = NULL, },
 352         { /* sentinel */ }
 353 };
 354 MODULE_DEVICE_TABLE(of, imx_rngc_dt_ids);
 355
 356 static struct platform_driver imx_rngc_driver = {
 357         .driver = {
 358                 .name = "imx_rngc",
 359                 .pm = &imx_rngc_pm_ops,
 360                 .of_match_table = imx_rngc_dt_ids,
 361         },
 362         .remove = __exit_p(imx_rngc_remove),
 363 };
 364
 365 module_platform_driver_probe(imx_rngc_driver, imx_rngc_probe);
 366
 367 MODULE_AUTHOR("Freescale Semiconductor, Inc.");
 368 MODULE_DESCRIPTION("H/W RNGC driver for i.MX");
 369 MODULE_LICENSE("GPL");