drivers/char/hw_random/stm32-rng.c

   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_address.h>
  14 #include <linux/of_platform.h>
  15 #include <linux/pm_runtime.h>
  16 #include <linux/reset.h>
  17 #include <linux/slab.h>
  18
  19 #define RNG_CR 0x00
  20 #define RNG_CR_RNGEN BIT(2)
  21 #define RNG_CR_CED BIT(5)
  22
  23 #define RNG_SR 0x04
  24 #define RNG_SR_SEIS BIT(6)
  25 #define RNG_SR_CEIS BIT(5)
  26 #define RNG_SR_DRDY BIT(0)
  27
  28 #define RNG_DR 0x08
  29
  30 struct stm32_rng_private {
  31         struct hwrng rng;
  32         void __iomem *base;
  33         struct clk *clk;
  34         struct reset_control *rst;
  35         bool ced;
  36 };
  37
  38 static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  39 {
  40         struct stm32_rng_private *priv =
  41             container_of(rng, struct stm32_rng_private, rng);
  42         u32 sr;
  43         int retval = 0;
  44
  45         pm_runtime_get_sync((struct device *) priv->rng.priv);
  46
  47         while (max >= sizeof(u32)) {
  48                 sr = readl_relaxed(priv->base + RNG_SR);
  49                 /* Manage timeout which is based on timer and take */
  50                 /* care of initial delay time when enabling rng */
  51                 if (!sr && wait) {
  52                         int err;
  53
  54                         err = readl_relaxed_poll_timeout_atomic(priv->base
  55                                                                    + RNG_SR,
  56                                                                    sr, sr,
  57                                                                    10, 50000);
  58                         if (err)
  59                                 dev_err((struct device *)priv->rng.priv,
  60                                         "%s: timeout %x!\n", __func__, sr);
  61                 }
  62
  63                 /* If error detected or data not ready... */
  64                 if (sr != RNG_SR_DRDY) {
  65                         if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
  66                                         "bad RNG status - %x\n", sr))
  67                                 writel_relaxed(0, priv->base + RNG_SR);
  68                         break;
  69                 }
  70
  71                 *(u32 *)data = readl_relaxed(priv->base + RNG_DR);
  72
  73                 retval += sizeof(u32);
  74                 data += sizeof(u32);
  75                 max -= sizeof(u32);
  76         }
  77
  78         pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
  79         pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
  80
  81         return retval || !wait ? retval : -EIO;
  82 }
  83
  84 static int stm32_rng_init(struct hwrng *rng)
  85 {
  86         struct stm32_rng_private *priv =
  87             container_of(rng, struct stm32_rng_private, rng);
  88         int err;
  89
  90         err = clk_prepare_enable(priv->clk);
  91         if (err)
  92                 return err;
  93
  94         if (priv->ced)
  95                 writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
  96         else
  97                 writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
  98                                priv->base + RNG_CR);
  99
 100         /* clear error indicators */
 101         writel_relaxed(0, priv->base + RNG_SR);
 102
 103         return 0;
 104 }
 105
 106 static void stm32_rng_cleanup(struct hwrng *rng)
 107 {
 108         struct stm32_rng_private *priv =
 109             container_of(rng, struct stm32_rng_private, rng);
 110
 111         writel_relaxed(0, priv->base + RNG_CR);
 112         clk_disable_unprepare(priv->clk);
 113 }
 114
 115 static int stm32_rng_probe(struct platform_device *ofdev)
 116 {
 117         struct device *dev = &ofdev->dev;
 118         struct device_node *np = ofdev->dev.of_node;
 119         struct stm32_rng_private *priv;
 120         struct resource res;
 121         int err;
 122
 123         priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
 124         if (!priv)
 125                 return -ENOMEM;
 126
 127         err = of_address_to_resource(np, 0, &res);
 128         if (err)
 129                 return err;
 130
 131         priv->base = devm_ioremap_resource(dev, &res);
 132         if (IS_ERR(priv->base))
 133                 return PTR_ERR(priv->base);
 134
 135         priv->clk = devm_clk_get(&ofdev->dev, NULL);
 136         if (IS_ERR(priv->clk))
 137                 return PTR_ERR(priv->clk);
 138
 139         priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
 140         if (!IS_ERR(priv->rst)) {
 141                 reset_control_assert(priv->rst);
 142                 udelay(2);
 143                 reset_control_deassert(priv->rst);
 144         }
 145
 146         priv->ced = of_property_read_bool(np, "clock-error-detect");
 147
 148         dev_set_drvdata(dev, priv);
 149
 150         priv->rng.name = dev_driver_string(dev);
 151 #ifndef CONFIG_PM
 152         priv->rng.init = stm32_rng_init;
 153         priv->rng.cleanup = stm32_rng_cleanup;
 154 #endif
 155         priv->rng.read = stm32_rng_read;
 156         priv->rng.priv = (unsigned long) dev;
 157         priv->rng.quality = 900;
 158
 159         pm_runtime_set_autosuspend_delay(dev, 100);
 160         pm_runtime_use_autosuspend(dev);
 161         pm_runtime_enable(dev);
 162
 163         return devm_hwrng_register(dev, &priv->rng);
 164 }
 165
 166 static int stm32_rng_remove(struct platform_device *ofdev)
 167 {
 168         pm_runtime_disable(&ofdev->dev);
 169
 170         return 0;
 171 }
 172
 173 #ifdef CONFIG_PM
 174 static int stm32_rng_runtime_suspend(struct device *dev)
 175 {
 176         struct stm32_rng_private *priv = dev_get_drvdata(dev);
 177
 178         stm32_rng_cleanup(&priv->rng);
 179
 180         return 0;
 181 }
 182
 183 static int stm32_rng_runtime_resume(struct device *dev)
 184 {
 185         struct stm32_rng_private *priv = dev_get_drvdata(dev);
 186
 187         return stm32_rng_init(&priv->rng);
 188 }
 189 #endif
 190
 191 static const struct dev_pm_ops stm32_rng_pm_ops = {
 192         SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
 193                            stm32_rng_runtime_resume, NULL)
 194         SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 195                                 pm_runtime_force_resume)
 196 };
 197
 198
 199 static const struct of_device_id stm32_rng_match[] = {
 200         {
 201                 .compatible = "st,stm32-rng",
 202         },
 203         {},
 204 };
 205 MODULE_DEVICE_TABLE(of, stm32_rng_match);
 206
 207 static struct platform_driver stm32_rng_driver = {
 208         .driver = {
 209                 .name = "stm32-rng",
 210                 .pm = &stm32_rng_pm_ops,
 211                 .of_match_table = stm32_rng_match,
 212         },
 213         .probe = stm32_rng_probe,
 214         .remove = stm32_rng_remove,
 215 };
 216
 217 module_platform_driver(stm32_rng_driver);
 218
 219 MODULE_LICENSE("GPL");
 220 MODULE_AUTHOR("Daniel Thompson <[email protected]>");
 221 MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");