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/mod_devicetable.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/delay.h>
  18
  19 /* Registers */
  20 #define RNG_CTRL_OFFSET                                 0x00
  21 #define RNG_CTRL_RNG_RBGEN_MASK                         0x00001FFF
  22 #define RNG_CTRL_RNG_RBGEN_ENABLE                       0x00000001
  23
  24 #define RNG_SOFT_RESET_OFFSET                           0x04
  25 #define RNG_SOFT_RESET                                  0x00000001
  26
  27 #define RBG_SOFT_RESET_OFFSET                           0x08
  28 #define RBG_SOFT_RESET                                  0x00000001
  29
  30 #define RNG_INT_STATUS_OFFSET                           0x18
  31 #define RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK     0x80000000
  32 #define RNG_INT_STATUS_STARTUP_TRANSITIONS_MET_IRQ_MASK 0x00020000
  33 #define RNG_INT_STATUS_NIST_FAIL_IRQ_MASK               0x00000020
  34 #define RNG_INT_STATUS_TOTAL_BITS_COUNT_IRQ_MASK        0x00000001
  35
  36 #define RNG_FIFO_DATA_OFFSET                            0x20
  37
  38 #define RNG_FIFO_COUNT_OFFSET                           0x24
  39 #define RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK              0x000000FF
  40
  41 struct iproc_rng200_dev {
  42         struct hwrng rng;
  43         void __iomem *base;
  44 };
  45
  46 #define to_rng_priv(rng)        container_of(rng, struct iproc_rng200_dev, rng)
  47
  48 static void iproc_rng200_enable_set(void __iomem *rng_base, bool enable)
  49 {
  50         u32 val;
  51
  52         val = ioread32(rng_base + RNG_CTRL_OFFSET);
  53         val &= ~RNG_CTRL_RNG_RBGEN_MASK;
  54
  55         if (enable)
  56                 val |= RNG_CTRL_RNG_RBGEN_ENABLE;
  57
  58         iowrite32(val, rng_base + RNG_CTRL_OFFSET);
  59 }
  60
  61 static void iproc_rng200_restart(void __iomem *rng_base)
  62 {
  63         uint32_t val;
  64
  65         iproc_rng200_enable_set(rng_base, false);
  66
  67         /* Clear all interrupt status */
  68         iowrite32(0xFFFFFFFFUL, rng_base + RNG_INT_STATUS_OFFSET);
  69
  70         /* Reset RNG and RBG */
  71         val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
  72         val |= RBG_SOFT_RESET;
  73         iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
  74
  75         val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
  76         val |= RNG_SOFT_RESET;
  77         iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
  78
  79         val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
  80         val &= ~RNG_SOFT_RESET;
  81         iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
  82
  83         val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
  84         val &= ~RBG_SOFT_RESET;
  85         iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
  86
  87         iproc_rng200_enable_set(rng_base, true);
  88 }
  89
  90 static int iproc_rng200_read(struct hwrng *rng, void *buf, size_t max,
  91                              bool wait)
  92 {
  93         struct iproc_rng200_dev *priv = to_rng_priv(rng);
  94         uint32_t num_remaining = max;
  95         uint32_t status;
  96
  97         #define MAX_RESETS_PER_READ     1
  98         uint32_t num_resets = 0;
  99
 100         #define MAX_IDLE_TIME   (1 * HZ)
 101         unsigned long idle_endtime = jiffies + MAX_IDLE_TIME;
 102
 103         while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {
 104
 105                 /* Is RNG sane? If not, reset it. */
 106                 status = ioread32(priv->base + RNG_INT_STATUS_OFFSET);
 107                 if ((status & (RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK |
 108                         RNG_INT_STATUS_NIST_FAIL_IRQ_MASK)) != 0) {
 109
 110                         if (num_resets >= MAX_RESETS_PER_READ)
 111                                 return max - num_remaining;
 112
 113                         iproc_rng200_restart(priv->base);
 114                         num_resets++;
 115                 }
 116
 117                 /* Are there any random numbers available? */
 118                 if ((ioread32(priv->base + RNG_FIFO_COUNT_OFFSET) &
 119                                 RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {
 120
 121                         if (num_remaining >= sizeof(uint32_t)) {
 122                                 /* Buffer has room to store entire word */
 123                                 *(uint32_t *)buf = ioread32(priv->base +
 124                                                         RNG_FIFO_DATA_OFFSET);
 125                                 buf += sizeof(uint32_t);
 126                                 num_remaining -= sizeof(uint32_t);
 127                         } else {
 128                                 /* Buffer can only store partial word */
 129                                 uint32_t rnd_number = ioread32(priv->base +
 130                                                         RNG_FIFO_DATA_OFFSET);
 131                                 memcpy(buf, &rnd_number, num_remaining);
 132                                 buf += num_remaining;
 133                                 num_remaining = 0;
 134                         }
 135
 136                         /* Reset the IDLE timeout */
 137                         idle_endtime = jiffies + MAX_IDLE_TIME;
 138                 } else {
 139                         if (!wait)
 140                                 /* Cannot wait, return immediately */
 141                                 return max - num_remaining;
 142
 143                         /* Can wait, give others chance to run */
 144                         usleep_range(min(num_remaining * 10, 500U), 500);
 145                 }
 146         }
 147
 148         return max - num_remaining;
 149 }
 150
 151 static int iproc_rng200_init(struct hwrng *rng)
 152 {
 153         struct iproc_rng200_dev *priv = to_rng_priv(rng);
 154
 155         iproc_rng200_enable_set(priv->base, true);
 156
 157         return 0;
 158 }
 159
 160 static void iproc_rng200_cleanup(struct hwrng *rng)
 161 {
 162         struct iproc_rng200_dev *priv = to_rng_priv(rng);
 163
 164         iproc_rng200_enable_set(priv->base, false);
 165 }
 166
 167 static int iproc_rng200_probe(struct platform_device *pdev)
 168 {
 169         struct iproc_rng200_dev *priv;
 170         struct device *dev = &pdev->dev;
 171         int ret;
 172
 173         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 174         if (!priv)
 175                 return -ENOMEM;
 176
 177         /* Map peripheral */
 178         priv->base = devm_platform_ioremap_resource(pdev, 0);
 179         if (IS_ERR(priv->base)) {
 180                 dev_err(dev, "failed to remap rng regs\n");
 181                 return PTR_ERR(priv->base);
 182         }
 183
 184         dev_set_drvdata(dev, priv);
 185
 186         priv->rng.name = "iproc-rng200";
 187         priv->rng.read = iproc_rng200_read;
 188         priv->rng.init = iproc_rng200_init;
 189         priv->rng.cleanup = iproc_rng200_cleanup;
 190
 191         /* Register driver */
 192         ret = devm_hwrng_register(dev, &priv->rng);
 193         if (ret) {
 194                 dev_err(dev, "hwrng registration failed\n");
 195                 return ret;
 196         }
 197
 198         dev_info(dev, "hwrng registered\n");
 199
 200         return 0;
 201 }
 202
 203 static int __maybe_unused iproc_rng200_suspend(struct device *dev)
 204 {
 205         struct iproc_rng200_dev *priv = dev_get_drvdata(dev);
 206
 207         iproc_rng200_cleanup(&priv->rng);
 208
 209         return 0;
 210 }
 211
 212 static int __maybe_unused iproc_rng200_resume(struct device *dev)
 213 {
 214         struct iproc_rng200_dev *priv =  dev_get_drvdata(dev);
 215
 216         iproc_rng200_init(&priv->rng);
 217
 218         return 0;
 219 }
 220
 221 static const struct dev_pm_ops iproc_rng200_pm_ops = {
 222         SET_SYSTEM_SLEEP_PM_OPS(iproc_rng200_suspend, iproc_rng200_resume)
 223 };
 224
 225 static const struct of_device_id iproc_rng200_of_match[] = {
 226         { .compatible = "brcm,bcm2711-rng200", },
 227         { .compatible = "brcm,bcm7211-rng200", },
 228         { .compatible = "brcm,bcm7278-rng200", },
 229         { .compatible = "brcm,iproc-rng200", },
 230         {},
 231 };
 232 MODULE_DEVICE_TABLE(of, iproc_rng200_of_match);
 233
 234 static struct platform_driver iproc_rng200_driver = {
 235         .driver = {
 236                 .name           = "iproc-rng200",
 237                 .of_match_table = iproc_rng200_of_match,
 238                 .pm             = &iproc_rng200_pm_ops,
 239         },
 240         .probe          = iproc_rng200_probe,
 241 };
 242 module_platform_driver(iproc_rng200_driver);
 243
 244 MODULE_AUTHOR("Broadcom");
 245 MODULE_DESCRIPTION("iProc RNG200 Random Number Generator driver");
 246 MODULE_LICENSE("GPL v2");