atmel-rng.c

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/*
 * Copyright (c) 2011 Peter Korsgaard <[email protected]>
 *
 * This file is licensed under  the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/hw_random.h>
#include <linux/platform_device.h>

#define TRNG_CR     0x00
#define TRNG_ISR    0x1c
#define TRNG_ODATA  0x50

#define TRNG_KEY    0x524e4700 /* RNG */

struct atmel_trng {
    struct clk *clk;
    void __iomem *base;
    struct hwrng rng;
};

static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
               bool wait)
{
    struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
    u32 *data = buf;

    /* data ready? */
    if (readl(trng->base + TRNG_ISR) & 1) {
        *data = readl(trng->base + TRNG_ODATA);
        /*
          ensure data ready is only set again AFTER the next data
          word is ready in case it got set between checking ISR
          and reading ODATA, so we don't risk re-reading the
          same word
        */
        readl(trng->base + TRNG_ISR);
        return 4;
    } else
        return 0;
}

static int atmel_trng_probe(struct platform_device *pdev)
{
    struct atmel_trng *trng;
    struct resource *res;
    int ret;

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res)
        return -EINVAL;

    trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
    if (!trng)
        return -ENOMEM;

    if (!devm_request_mem_region(&pdev->dev, res->start,
                     resource_size(res), pdev->name))
        return -EBUSY;

    trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
    if (!trng->base)
        return -EBUSY;

    trng->clk = clk_get(&pdev->dev, NULL);
    if (IS_ERR(trng->clk))
        return PTR_ERR(trng->clk);

    ret = clk_enable(trng->clk);
    if (ret)
        goto err_enable;

    writel(TRNG_KEY | 1, trng->base + TRNG_CR);
    trng->rng.name = pdev->name;
    trng->rng.read = atmel_trng_read;

    ret = hwrng_register(&trng->rng);
    if (ret)
        goto err_register;

    platform_set_drvdata(pdev, trng);

    return 0;

err_register:
    clk_disable(trng->clk);
err_enable:
    clk_put(trng->clk);

    return ret;
}

static int __devexit atmel_trng_remove(struct platform_device *pdev)
{
    struct atmel_trng *trng = platform_get_drvdata(pdev);

    hwrng_unregister(&trng->rng);

    writel(TRNG_KEY, trng->base + TRNG_CR);
    clk_disable(trng->clk);
    clk_put(trng->clk);

    platform_set_drvdata(pdev, NULL);

    return 0;
}

#ifdef CONFIG_PM
static int atmel_trng_suspend(struct device *dev)
{
    struct atmel_trng *trng = dev_get_drvdata(dev);

    clk_disable(trng->clk);

    return 0;
}

static int atmel_trng_resume(struct device *dev)
{
    struct atmel_trng *trng = dev_get_drvdata(dev);

    return clk_enable(trng->clk);
}

static const struct dev_pm_ops atmel_trng_pm_ops = {
    .suspend    = atmel_trng_suspend,
    .resume     = atmel_trng_resume,
};
#endif /* CONFIG_PM */

static struct platform_driver atmel_trng_driver = {
    .probe      = atmel_trng_probe,
    .remove     = __devexit_p(atmel_trng_remove),
    .driver     = {
        .name   = "atmel-trng",
        .owner  = THIS_MODULE,
#ifdef CONFIG_PM
        .pm = &atmel_trng_pm_ops,
#endif /* CONFIG_PM */
    },
};

module_platform_driver(atmel_trng_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Peter Korsgaard <[email protected]>");
MODULE_DESCRIPTION("Atmel true random number generator driver");