omap-rng.c

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/*
 * omap-rng.c - RNG driver for TI OMAP CPU family
 *
 * Author: Deepak Saxena <[email protected]>
 *
 * Copyright 2005 (c) MontaVista Software, Inc.
 *
 * Mostly based on original driver:
 *
 * Copyright (C) 2005 Nokia Corporation
 * Author: Juha Yrjölä <[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/module.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>

#include <asm/io.h>

#include <plat/cpu.h>

#define RNG_OUT_REG     0x00        /* Output register */
#define RNG_STAT_REG        0x04        /* Status register
                            [0] = STAT_BUSY */
#define RNG_ALARM_REG       0x24        /* Alarm register
                            [7:0] = ALARM_COUNTER */
#define RNG_CONFIG_REG      0x28        /* Configuration register
                            [11:6] = RESET_COUNT
                            [5:3]  = RING2_DELAY
                            [2:0]  = RING1_DELAY */
#define RNG_REV_REG     0x3c        /* Revision register
                            [7:0] = REV_NB */
#define RNG_MASK_REG        0x40        /* Mask and reset register
                            [2] = IT_EN
                            [1] = SOFTRESET
                            [0] = AUTOIDLE */
#define RNG_SYSSTATUS       0x44        /* System status
                            [0] = RESETDONE */

struct omap_rng_private_data {
    void __iomem *base;
    struct resource *mem_res;
};

static inline u32 omap_rng_read_reg(struct omap_rng_private_data *priv, int reg)
{
    return __raw_readl(priv->base + reg);
}

static inline void omap_rng_write_reg(struct omap_rng_private_data *priv,
                      int reg, u32 val)
{
    __raw_writel(val, priv->base + reg);
}

static int omap_rng_data_present(struct hwrng *rng, int wait)
{
    struct omap_rng_private_data *priv;
    int data, i;

    priv = (struct omap_rng_private_data *)rng->priv;

    for (i = 0; i < 20; i++) {
        data = omap_rng_read_reg(priv, RNG_STAT_REG) ? 0 : 1;
        if (data || !wait)
            break;
        /* RNG produces data fast enough (2+ MBit/sec, even
         * during "rngtest" loads, that these delays don't
         * seem to trigger.  We *could* use the RNG IRQ, but
         * that'd be higher overhead ... so why bother?
         */
        udelay(10);
    }
    return data;
}

static int omap_rng_data_read(struct hwrng *rng, u32 *data)
{
    struct omap_rng_private_data *priv;

    priv = (struct omap_rng_private_data *)rng->priv;

    *data = omap_rng_read_reg(priv, RNG_OUT_REG);

    return sizeof(u32);
}

static struct hwrng omap_rng_ops = {
    .name       = "omap",
    .data_present   = omap_rng_data_present,
    .data_read  = omap_rng_data_read,
};

static int __devinit omap_rng_probe(struct platform_device *pdev)
{
    struct omap_rng_private_data *priv;
    int ret;

    priv = kzalloc(sizeof(struct omap_rng_private_data), GFP_KERNEL);
    if (!priv) {
        dev_err(&pdev->dev, "could not allocate memory\n");
        return -ENOMEM;
    };

    omap_rng_ops.priv = (unsigned long)priv;
    dev_set_drvdata(&pdev->dev, priv);

    priv->mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!priv->mem_res) {
        ret = -ENOENT;
        goto err_ioremap;
    }

    priv->base = devm_request_and_ioremap(&pdev->dev, priv->mem_res);
    if (!priv->base) {
        ret = -ENOMEM;
        goto err_ioremap;
    }
    dev_set_drvdata(&pdev->dev, priv);

    pm_runtime_enable(&pdev->dev);
    pm_runtime_get_sync(&pdev->dev);

    ret = hwrng_register(&omap_rng_ops);
    if (ret)
        goto err_register;

    dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x\n",
         omap_rng_read_reg(priv, RNG_REV_REG));

    omap_rng_write_reg(priv, RNG_MASK_REG, 0x1);

    return 0;

err_register:
    priv->base = NULL;
    pm_runtime_disable(&pdev->dev);
err_ioremap:
    kfree(priv);

    return ret;
}

static int __exit omap_rng_remove(struct platform_device *pdev)
{
    struct omap_rng_private_data *priv = dev_get_drvdata(&pdev->dev);

    hwrng_unregister(&omap_rng_ops);

    omap_rng_write_reg(priv, RNG_MASK_REG, 0x0);

    pm_runtime_put_sync(&pdev->dev);
    pm_runtime_disable(&pdev->dev);

    release_mem_region(priv->mem_res->start, resource_size(priv->mem_res));

    kfree(priv);

    return 0;
}

#ifdef CONFIG_PM_SLEEP

static int omap_rng_suspend(struct device *dev)
{
    struct omap_rng_private_data *priv = dev_get_drvdata(dev);

    omap_rng_write_reg(priv, RNG_MASK_REG, 0x0);
    pm_runtime_put_sync(dev);

    return 0;
}

static int omap_rng_resume(struct device *dev)
{
    struct omap_rng_private_data *priv = dev_get_drvdata(dev);

    pm_runtime_get_sync(dev);
    omap_rng_write_reg(priv, RNG_MASK_REG, 0x1);

    return 0;
}

static SIMPLE_DEV_PM_OPS(omap_rng_pm, omap_rng_suspend, omap_rng_resume);
#define OMAP_RNG_PM (&omap_rng_pm)

#else

#define OMAP_RNG_PM NULL

#endif

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:omap_rng");

static struct platform_driver omap_rng_driver = {
    .driver = {
        .name       = "omap_rng",
        .owner      = THIS_MODULE,
        .pm     = OMAP_RNG_PM,
    },
    .probe      = omap_rng_probe,
    .remove     = __exit_p(omap_rng_remove),
};

static int __init omap_rng_init(void)
{
    return platform_driver_register(&omap_rng_driver);
}

static void __exit omap_rng_exit(void)
{
    platform_driver_unregister(&omap_rng_driver);
}

module_init(omap_rng_init);
module_exit(omap_rng_exit);

MODULE_AUTHOR("Deepak Saxena (and others)");
MODULE_LICENSE("GPL");