drivers/char/hw_random/stm32-rng.c

   1 /*
   2  * Copyright (c) 2015, Daniel Thompson
   3  *
   4  * This file is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This file is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <linux/clk.h>
  16 #include <linux/delay.h>
  17 #include <linux/hw_random.h>
  18 #include <linux/io.h>
  19 #include <linux/iopoll.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/of_address.h>
  23 #include <linux/of_platform.h>
  24 #include <linux/pm_runtime.h>
  25 #include <linux/reset.h>
  26 #include <linux/slab.h>
  27
  28 #define RNG_CR 0x00
  29 #define RNG_CR_RNGEN BIT(2)
  30 #define RNG_CR_CED BIT(5)
  31
  32 #define RNG_SR 0x04
  33 #define RNG_SR_SEIS BIT(6)
  34 #define RNG_SR_CEIS BIT(5)
  35 #define RNG_SR_DRDY BIT(0)
  36
  37 #define RNG_DR 0x08
  38
  39 struct stm32_rng_private {
  40         struct hwrng rng;
  41         void __iomem *base;
  42         struct clk *clk;
  43         struct reset_control *rst;
  44         bool ced;
  45 };
  46
  47 static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
  48 {
  49         struct stm32_rng_private *priv =
  50             container_of(rng, struct stm32_rng_private, rng);
  51         u32 sr;
  52         int retval = 0;
  53
  54         pm_runtime_get_sync((struct device *) priv->rng.priv);
  55
  56         while (max > sizeof(u32)) {
  57                 sr = readl_relaxed(priv->base + RNG_SR);
  58                 /* Manage timeout which is based on timer and take */
  59                 /* care of initial delay time when enabling rng */
  60                 if (!sr && wait) {
  61                         retval = readl_relaxed_poll_timeout_atomic(priv->base
  62                                                                    + RNG_SR,
  63                                                                    sr, sr,
  64                                                                    10, 50000);
  65                         if (retval)
  66                                 dev_err((struct device *)priv->rng.priv,
  67                                         "%s: timeout %x!\n", __func__, sr);
  68                 }
  69
  70                 /* If error detected or data not ready... */
  71                 if (sr != RNG_SR_DRDY) {
  72                         if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),
  73                                         "bad RNG status - %x\n", sr))
  74                                 writel_relaxed(0, priv->base + RNG_SR);
  75                         break;
  76                 }
  77
  78                 *(u32 *)data = readl_relaxed(priv->base + RNG_DR);
  79
  80                 retval += sizeof(u32);
  81                 data += sizeof(u32);
  82                 max -= sizeof(u32);
  83         }
  84
  85         pm_runtime_mark_last_busy((struct device *) priv->rng.priv);
  86         pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv);
  87
  88         return retval || !wait ? retval : -EIO;
  89 }
  90
  91 static int stm32_rng_init(struct hwrng *rng)
  92 {
  93         struct stm32_rng_private *priv =
  94             container_of(rng, struct stm32_rng_private, rng);
  95         int err;
  96
  97         err = clk_prepare_enable(priv->clk);
  98         if (err)
  99                 return err;
 100
 101         if (priv->ced)
 102                 writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
 103         else
 104                 writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
 105                                priv->base + RNG_CR);
 106
 107         /* clear error indicators */
 108         writel_relaxed(0, priv->base + RNG_SR);
 109
 110         return 0;
 111 }
 112
 113 static void stm32_rng_cleanup(struct hwrng *rng)
 114 {
 115         struct stm32_rng_private *priv =
 116             container_of(rng, struct stm32_rng_private, rng);
 117
 118         writel_relaxed(0, priv->base + RNG_CR);
 119         clk_disable_unprepare(priv->clk);
 120 }
 121
 122 static int stm32_rng_probe(struct platform_device *ofdev)
 123 {
 124         struct device *dev = &ofdev->dev;
 125         struct device_node *np = ofdev->dev.of_node;
 126         struct stm32_rng_private *priv;
 127         struct resource res;
 128         int err;
 129
 130         priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
 131         if (!priv)
 132                 return -ENOMEM;
 133
 134         err = of_address_to_resource(np, 0, &res);
 135         if (err)
 136                 return err;
 137
 138         priv->base = devm_ioremap_resource(dev, &res);
 139         if (IS_ERR(priv->base))
 140                 return PTR_ERR(priv->base);
 141
 142         priv->clk = devm_clk_get(&ofdev->dev, NULL);
 143         if (IS_ERR(priv->clk))
 144                 return PTR_ERR(priv->clk);
 145
 146         priv->rst = devm_reset_control_get(&ofdev->dev, NULL);
 147         if (!IS_ERR(priv->rst)) {
 148                 reset_control_assert(priv->rst);
 149                 udelay(2);
 150                 reset_control_deassert(priv->rst);
 151         }
 152
 153         priv->ced = of_property_read_bool(np, "clock-error-detect");
 154
 155         dev_set_drvdata(dev, priv);
 156
 157         priv->rng.name = dev_driver_string(dev),
 158 #ifndef CONFIG_PM
 159         priv->rng.init = stm32_rng_init,
 160         priv->rng.cleanup = stm32_rng_cleanup,
 161 #endif
 162         priv->rng.read = stm32_rng_read,
 163         priv->rng.priv = (unsigned long) dev;
 164
 165         pm_runtime_set_autosuspend_delay(dev, 100);
 166         pm_runtime_use_autosuspend(dev);
 167         pm_runtime_enable(dev);
 168
 169         return devm_hwrng_register(dev, &priv->rng);
 170 }
 171
 172 #ifdef CONFIG_PM
 173 static int stm32_rng_runtime_suspend(struct device *dev)
 174 {
 175         struct stm32_rng_private *priv = dev_get_drvdata(dev);
 176
 177         stm32_rng_cleanup(&priv->rng);
 178
 179         return 0;
 180 }
 181
 182 static int stm32_rng_runtime_resume(struct device *dev)
 183 {
 184         struct stm32_rng_private *priv = dev_get_drvdata(dev);
 185
 186         return stm32_rng_init(&priv->rng);
 187 }
 188 #endif
 189
 190 static const struct dev_pm_ops stm32_rng_pm_ops = {
 191         SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
 192                            stm32_rng_runtime_resume, NULL)
 193         SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 194                                 pm_runtime_force_resume)
 195 };
 196
 197
 198 static const struct of_device_id stm32_rng_match[] = {
 199         {
 200                 .compatible = "st,stm32-rng",
 201         },
 202         {},
 203 };
 204 MODULE_DEVICE_TABLE(of, stm32_rng_match);
 205
 206 static struct platform_driver stm32_rng_driver = {
 207         .driver = {
 208                 .name = "stm32-rng",
 209                 .pm = &stm32_rng_pm_ops,
 210                 .of_match_table = stm32_rng_match,
 211         },
 212         .probe = stm32_rng_probe,
 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");