drivers/char/hw_random/iproc-rng200.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3 * Copyright (C) 2015 Broadcom Corporation
   4 *
   5 */
   6 /*
   7  * DESCRIPTION: The Broadcom iProc RNG200 Driver
   8  */
   9
  10 #include <linux/hw_random.h>
  11 #include <linux/init.h>
  12 #include <linux/io.h>
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/of_address.h>
  16 #include <linux/of_platform.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/delay.h>
  19
  20 /* Registers */
  21 #define RNG_CTRL_OFFSET                                 0x00
  22 #define RNG_CTRL_RNG_RBGEN_MASK                         0x00001FFF
  23 #define RNG_CTRL_RNG_RBGEN_ENABLE                       0x00000001
  24
  25 #define RNG_SOFT_RESET_OFFSET                           0x04
  26 #define RNG_SOFT_RESET                                  0x00000001
  27
  28 #define RBG_SOFT_RESET_OFFSET                           0x08
  29 #define RBG_SOFT_RESET                                  0x00000001
  30
  31 #define RNG_INT_STATUS_OFFSET                           0x18
  32 #define RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK     0x80000000
  33 #define RNG_INT_STATUS_STARTUP_TRANSITIONS_MET_IRQ_MASK 0x00020000
  34 #define RNG_INT_STATUS_NIST_FAIL_IRQ_MASK               0x00000020
  35 #define RNG_INT_STATUS_TOTAL_BITS_COUNT_IRQ_MASK        0x00000001
  36
  37 #define RNG_FIFO_DATA_OFFSET                            0x20
  38
  39 #define RNG_FIFO_COUNT_OFFSET                           0x24
  40 #define RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK              0x000000FF
  41
  42 struct iproc_rng200_dev {
  43         struct hwrng rng;
  44         void __iomem *base;
  45 };
  46
  47 #define to_rng_priv(rng)        container_of(rng, struct iproc_rng200_dev, rng)
  48
  49 static void iproc_rng200_enable_set(void __iomem *rng_base, bool enable)
  50 {
  51         u32 val;
  52
  53         val = ioread32(rng_base + RNG_CTRL_OFFSET);
  54         val &= ~RNG_CTRL_RNG_RBGEN_MASK;
  55
  56         if (enable)
  57                 val |= RNG_CTRL_RNG_RBGEN_ENABLE;
  58
  59         iowrite32(val, rng_base + RNG_CTRL_OFFSET);
  60 }
  61
  62 static void iproc_rng200_restart(void __iomem *rng_base)
  63 {
  64         uint32_t val;
  65
  66         iproc_rng200_enable_set(rng_base, false);
  67
  68         /* Clear all interrupt status */
  69         iowrite32(0xFFFFFFFFUL, rng_base + RNG_INT_STATUS_OFFSET);
  70
  71         /* Reset RNG and RBG */
  72         val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
  73         val |= RBG_SOFT_RESET;
  74         iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
  75
  76         val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
  77         val |= RNG_SOFT_RESET;
  78         iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
  79
  80         val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
  81         val &= ~RNG_SOFT_RESET;
  82         iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
  83
  84         val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
  85         val &= ~RBG_SOFT_RESET;
  86         iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
  87
  88         iproc_rng200_enable_set(rng_base, true);
  89 }
  90
  91 static int iproc_rng200_read(struct hwrng *rng, void *buf, size_t max,
  92                              bool wait)
  93 {
  94         struct iproc_rng200_dev *priv = to_rng_priv(rng);
  95         uint32_t num_remaining = max;
  96         uint32_t status;
  97
  98         #define MAX_RESETS_PER_READ     1
  99         uint32_t num_resets = 0;
 100
 101         #define MAX_IDLE_TIME   (1 * HZ)
 102         unsigned long idle_endtime = jiffies + MAX_IDLE_TIME;
 103
 104         while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {
 105
 106                 /* Is RNG sane? If not, reset it. */
 107                 status = ioread32(priv->base + RNG_INT_STATUS_OFFSET);
 108                 if ((status & (RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK |
 109                         RNG_INT_STATUS_NIST_FAIL_IRQ_MASK)) != 0) {
 110
 111                         if (num_resets >= MAX_RESETS_PER_READ)
 112                                 return max - num_remaining;
 113
 114                         iproc_rng200_restart(priv->base);
 115                         num_resets++;
 116                 }
 117
 118                 /* Are there any random numbers available? */
 119                 if ((ioread32(priv->base + RNG_FIFO_COUNT_OFFSET) &
 120                                 RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {
 121
 122                         if (num_remaining >= sizeof(uint32_t)) {
 123                                 /* Buffer has room to store entire word */
 124                                 *(uint32_t *)buf = ioread32(priv->base +
 125                                                         RNG_FIFO_DATA_OFFSET);
 126                                 buf += sizeof(uint32_t);
 127                                 num_remaining -= sizeof(uint32_t);
 128                         } else {
 129                                 /* Buffer can only store partial word */
 130                                 uint32_t rnd_number = ioread32(priv->base +
 131                                                         RNG_FIFO_DATA_OFFSET);
 132                                 memcpy(buf, &rnd_number, num_remaining);
 133                                 buf += num_remaining;
 134                                 num_remaining = 0;
 135                         }
 136
 137                         /* Reset the IDLE timeout */
 138                         idle_endtime = jiffies + MAX_IDLE_TIME;
 139                 } else {
 140                         if (!wait)
 141                                 /* Cannot wait, return immediately */
 142                                 return max - num_remaining;
 143
 144                         /* Can wait, give others chance to run */
 145                         usleep_range(min(num_remaining * 10, 500U), 500);
 146                 }
 147         }
 148
 149         return max - num_remaining;
 150 }
 151
 152 static int iproc_rng200_init(struct hwrng *rng)
 153 {
 154         struct iproc_rng200_dev *priv = to_rng_priv(rng);
 155
 156         iproc_rng200_enable_set(priv->base, true);
 157
 158         return 0;
 159 }
 160
 161 static void iproc_rng200_cleanup(struct hwrng *rng)
 162 {
 163         struct iproc_rng200_dev *priv = to_rng_priv(rng);
 164
 165         iproc_rng200_enable_set(priv->base, false);
 166 }
 167
 168 static int iproc_rng200_probe(struct platform_device *pdev)
 169 {
 170         struct iproc_rng200_dev *priv;
 171         struct device *dev = &pdev->dev;
 172         int ret;
 173
 174         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 175         if (!priv)
 176                 return -ENOMEM;
 177
 178         /* Map peripheral */
 179         priv->base = devm_platform_ioremap_resource(pdev, 0);
 180         if (IS_ERR(priv->base)) {
 181                 dev_err(dev, "failed to remap rng regs\n");
 182                 return PTR_ERR(priv->base);
 183         }
 184
 185         priv->rng.name = "iproc-rng200";
 186         priv->rng.read = iproc_rng200_read;
 187         priv->rng.init = iproc_rng200_init;
 188         priv->rng.cleanup = iproc_rng200_cleanup;
 189
 190         /* Register driver */
 191         ret = devm_hwrng_register(dev, &priv->rng);
 192         if (ret) {
 193                 dev_err(dev, "hwrng registration failed\n");
 194                 return ret;
 195         }
 196
 197         dev_info(dev, "hwrng registered\n");
 198
 199         return 0;
 200 }
 201
 202 static const struct of_device_id iproc_rng200_of_match[] = {
 203         { .compatible = "brcm,bcm2711-rng200", },
 204         { .compatible = "brcm,bcm7211-rng200", },
 205         { .compatible = "brcm,bcm7278-rng200", },
 206         { .compatible = "brcm,iproc-rng200", },
 207         {},
 208 };
 209 MODULE_DEVICE_TABLE(of, iproc_rng200_of_match);
 210
 211 static struct platform_driver iproc_rng200_driver = {
 212         .driver = {
 213                 .name           = "iproc-rng200",
 214                 .of_match_table = iproc_rng200_of_match,
 215         },
 216         .probe          = iproc_rng200_probe,
 217 };
 218 module_platform_driver(iproc_rng200_driver);
 219
 220 MODULE_AUTHOR("Broadcom");
 221 MODULE_DESCRIPTION("iProc RNG200 Random Number Generator driver");
 222 MODULE_LICENSE("GPL v2");