LXR linux/drivers/char/hw_random/atmel-rng.c

   1/*
   2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
   3 *
   4 * This file is licensed under  the terms of the GNU General Public
   5 * License version 2. This program is licensed "as is" without any
   6 * warranty of any kind, whether express or implied.
   7 */
   8
   9#include <linux/kernel.h>
  10#include <linux/module.h>
  11#include <linux/slab.h>
  12#include <linux/err.h>
  13#include <linux/clk.h>
  14#include <linux/io.h>
  15#include <linux/hw_random.h>
  16#include <linux/platform_device.h>
  17
  18#define TRNG_CR         0x00
  19#define TRNG_ISR        0x1c
  20#define TRNG_ODATA      0x50
  21
  22#define TRNG_KEY        0x524e4700 /* RNG */
  23
  24struct atmel_trng {
  25        struct clk *clk;
  26        void __iomem *base;
  27        struct hwrng rng;
  28};
  29
  30static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
  31                           bool wait)
  32{
  33        struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
  34        u32 *data = buf;
  35
  36        /* data ready? */
  37        if (readl(trng->base + TRNG_ISR) & 1) {
  38                *data = readl(trng->base + TRNG_ODATA);
  39                /*
  40                  ensure data ready is only set again AFTER the next data
  41                  word is ready in case it got set between checking ISR
  42                  and reading ODATA, so we don't risk re-reading the
  43                  same word
  44                */
  45                readl(trng->base + TRNG_ISR);
  46                return 4;
  47        } else
  48                return 0;
  49}
  50
  51static int atmel_trng_probe(struct platform_device *pdev)
  52{
  53        struct atmel_trng *trng;
  54        struct resource *res;
  55        int ret;
  56
  57        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  58        if (!res)
  59                return -EINVAL;
  60
  61        trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  62        if (!trng)
  63                return -ENOMEM;
  64
  65        if (!devm_request_mem_region(&pdev->dev, res->start,
  66                                     resource_size(res), pdev->name))
  67                return -EBUSY;
  68
  69        trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
  70        if (!trng->base)
  71                return -EBUSY;
  72
  73        trng->clk = clk_get(&pdev->dev, NULL);
  74        if (IS_ERR(trng->clk))
  75                return PTR_ERR(trng->clk);
  76
  77        ret = clk_enable(trng->clk);
  78        if (ret)
  79                goto err_enable;
  80
  81        writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  82        trng->rng.name = pdev->name;
  83        trng->rng.read = atmel_trng_read;
  84
  85        ret = hwrng_register(&trng->rng);
  86        if (ret)
  87                goto err_register;
  88
  89        platform_set_drvdata(pdev, trng);
  90
  91        return 0;
  92
  93err_register:
  94        clk_disable(trng->clk);
  95err_enable:
  96        clk_put(trng->clk);
  97
  98        return ret;
  99}
 100
 101static int atmel_trng_remove(struct platform_device *pdev)
 102{
 103        struct atmel_trng *trng = platform_get_drvdata(pdev);
 104
 105        hwrng_unregister(&trng->rng);
 106
 107        writel(TRNG_KEY, trng->base + TRNG_CR);
 108        clk_disable(trng->clk);
 109        clk_put(trng->clk);
 110
 111        platform_set_drvdata(pdev, NULL);
 112
 113        return 0;
 114}
 115
 116#ifdef CONFIG_PM
 117static int atmel_trng_suspend(struct device *dev)
 118{
 119        struct atmel_trng *trng = dev_get_drvdata(dev);
 120
 121        clk_disable(trng->clk);
 122
 123        return 0;
 124}
 125
 126static int atmel_trng_resume(struct device *dev)
 127{
 128        struct atmel_trng *trng = dev_get_drvdata(dev);
 129
 130        return clk_enable(trng->clk);
 131}
 132
 133static const struct dev_pm_ops atmel_trng_pm_ops = {
 134        .suspend        = atmel_trng_suspend,
 135        .resume         = atmel_trng_resume,
 136};
 137#endif /* CONFIG_PM */
 138
 139static struct platform_driver atmel_trng_driver = {
 140        .probe          = atmel_trng_probe,
 141        .remove         = atmel_trng_remove,
 142        .driver         = {
 143                .name   = "atmel-trng",
 144                .owner  = THIS_MODULE,
 145#ifdef CONFIG_PM
 146                .pm     = &atmel_trng_pm_ops,
 147#endif /* CONFIG_PM */
 148        },
 149};
 150
 151module_platform_driver(atmel_trng_driver);
 152
 153MODULE_LICENSE("GPL");
 154MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 155MODULE_DESCRIPTION("Atmel true random number generator driver");
 156