linux/drivers/char/hw_random/stm32-rng.c
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   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
  30struct 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
  38static 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
  82static 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
 104static 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
 113static 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
 164static 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
 172static 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
 181static 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
 189static 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
 197static const struct of_device_id stm32_rng_match[] = {
 198        {
 199                .compatible = "st,stm32-rng",
 200        },
 201        {},
 202};
 203MODULE_DEVICE_TABLE(of, stm32_rng_match);
 204
 205static 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
 215module_platform_driver(stm32_rng_driver);
 216
 217MODULE_LICENSE("GPL");
 218MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>");
 219MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");
 220
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