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 void atmel_trng_enable(struct atmel_trng *trng)
  52{
  53        writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  54}
  55
  56static void atmel_trng_disable(struct atmel_trng *trng)
  57{
  58        writel(TRNG_KEY, trng->base + TRNG_CR);
  59}
  60
  61static int atmel_trng_probe(struct platform_device *pdev)
  62{
  63        struct atmel_trng *trng;
  64        struct resource *res;
  65        int ret;
  66
  67        trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  68        if (!trng)
  69                return -ENOMEM;
  70
  71        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  72        trng->base = devm_ioremap_resource(&pdev->dev, res);
  73        if (IS_ERR(trng->base))
  74                return PTR_ERR(trng->base);
  75
  76        trng->clk = devm_clk_get(&pdev->dev, NULL);
  77        if (IS_ERR(trng->clk))
  78                return PTR_ERR(trng->clk);
  79
  80        ret = clk_prepare_enable(trng->clk);
  81        if (ret)
  82                return ret;
  83
  84        atmel_trng_enable(trng);
  85        trng->rng.name = pdev->name;
  86        trng->rng.read = atmel_trng_read;
  87
  88        ret = hwrng_register(&trng->rng);
  89        if (ret)
  90                goto err_register;
  91
  92        platform_set_drvdata(pdev, trng);
  93
  94        return 0;
  95
  96err_register:
  97        clk_disable_unprepare(trng->clk);
  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        atmel_trng_disable(trng);
 108        clk_disable_unprepare(trng->clk);
 109
 110        return 0;
 111}
 112
 113#ifdef CONFIG_PM
 114static int atmel_trng_suspend(struct device *dev)
 115{
 116        struct atmel_trng *trng = dev_get_drvdata(dev);
 117
 118        atmel_trng_disable(trng);
 119        clk_disable_unprepare(trng->clk);
 120
 121        return 0;
 122}
 123
 124static int atmel_trng_resume(struct device *dev)
 125{
 126        struct atmel_trng *trng = dev_get_drvdata(dev);
 127        int ret;
 128
 129        ret = clk_prepare_enable(trng->clk);
 130        if (ret)
 131                return ret;
 132
 133        atmel_trng_enable(trng);
 134
 135        return 0;
 136}
 137
 138static const struct dev_pm_ops atmel_trng_pm_ops = {
 139        .suspend        = atmel_trng_suspend,
 140        .resume         = atmel_trng_resume,
 141};
 142#endif /* CONFIG_PM */
 143
 144static const struct of_device_id atmel_trng_dt_ids[] = {
 145        { .compatible = "atmel,at91sam9g45-trng" },
 146        { /* sentinel */ }
 147};
 148MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 149
 150static struct platform_driver atmel_trng_driver = {
 151        .probe          = atmel_trng_probe,
 152        .remove         = atmel_trng_remove,
 153        .driver         = {
 154                .name   = "atmel-trng",
 155#ifdef CONFIG_PM
 156                .pm     = &atmel_trng_pm_ops,
 157#endif /* CONFIG_PM */
 158                .of_match_table = atmel_trng_dt_ids,
 159        },
 160};
 161
 162module_platform_driver(atmel_trng_driver);
 163
 164MODULE_LICENSE("GPL");
 165MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 166MODULE_DESCRIPTION("Atmel true random number generator driver");
 167