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        trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  58        if (!trng)
  59                return -ENOMEM;
  60
  61        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  62        trng->base = devm_ioremap_resource(&pdev->dev, res);
  63        if (IS_ERR(trng->base))
  64                return PTR_ERR(trng->base);
  65
  66        trng->clk = devm_clk_get(&pdev->dev, NULL);
  67        if (IS_ERR(trng->clk))
  68                return PTR_ERR(trng->clk);
  69
  70        ret = clk_prepare_enable(trng->clk);
  71        if (ret)
  72                return ret;
  73
  74        writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  75        trng->rng.name = pdev->name;
  76        trng->rng.read = atmel_trng_read;
  77
  78        ret = hwrng_register(&trng->rng);
  79        if (ret)
  80                goto err_register;
  81
  82        platform_set_drvdata(pdev, trng);
  83
  84        return 0;
  85
  86err_register:
  87        clk_disable(trng->clk);
  88        return ret;
  89}
  90
  91static int atmel_trng_remove(struct platform_device *pdev)
  92{
  93        struct atmel_trng *trng = platform_get_drvdata(pdev);
  94
  95        hwrng_unregister(&trng->rng);
  96
  97        writel(TRNG_KEY, trng->base + TRNG_CR);
  98        clk_disable_unprepare(trng->clk);
  99
 100        return 0;
 101}
 102
 103#ifdef CONFIG_PM
 104static int atmel_trng_suspend(struct device *dev)
 105{
 106        struct atmel_trng *trng = dev_get_drvdata(dev);
 107
 108        clk_disable_unprepare(trng->clk);
 109
 110        return 0;
 111}
 112
 113static int atmel_trng_resume(struct device *dev)
 114{
 115        struct atmel_trng *trng = dev_get_drvdata(dev);
 116
 117        return clk_prepare_enable(trng->clk);
 118}
 119
 120static const struct dev_pm_ops atmel_trng_pm_ops = {
 121        .suspend        = atmel_trng_suspend,
 122        .resume         = atmel_trng_resume,
 123};
 124#endif /* CONFIG_PM */
 125
 126static const struct of_device_id atmel_trng_dt_ids[] = {
 127        { .compatible = "atmel,at91sam9g45-trng" },
 128        { /* sentinel */ }
 129};
 130MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 131
 132static struct platform_driver atmel_trng_driver = {
 133        .probe          = atmel_trng_probe,
 134        .remove         = atmel_trng_remove,
 135        .driver         = {
 136                .name   = "atmel-trng",
 137#ifdef CONFIG_PM
 138                .pm     = &atmel_trng_pm_ops,
 139#endif /* CONFIG_PM */
 140                .of_match_table = atmel_trng_dt_ids,
 141        },
 142};
 143
 144module_platform_driver(atmel_trng_driver);
 145
 146MODULE_LICENSE("GPL");
 147MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 148MODULE_DESCRIPTION("Atmel true random number generator driver");
 149