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