ppc4xx-rng.c

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/*
 * Generic PowerPC 44x RNG driver
 *
 * Copyright 2011 IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; version 2 of the License.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/delay.h>
#include <linux/of_platform.h>
#include <asm/io.h>

#define PPC4XX_TRNG_DEV_CTRL 0x60080

#define PPC4XX_TRNGE 0x00020000
#define PPC4XX_TRNG_CTRL 0x0008
#define PPC4XX_TRNG_CTRL_DALM 0x20
#define PPC4XX_TRNG_STAT 0x0004
#define PPC4XX_TRNG_STAT_B 0x1
#define PPC4XX_TRNG_DATA 0x0000

#define MODULE_NAME "ppc4xx_rng"

static int ppc4xx_rng_data_present(struct hwrng *rng, int wait)
{
    void __iomem *rng_regs = (void __iomem *) rng->priv;
    int busy, i, present = 0;

    for (i = 0; i < 20; i++) {
        busy = (in_le32(rng_regs + PPC4XX_TRNG_STAT) & PPC4XX_TRNG_STAT_B);
        if (!busy || !wait) {
            present = 1;
            break;
        }
        udelay(10);
    }
    return present;
}

static int ppc4xx_rng_data_read(struct hwrng *rng, u32 *data)
{
    void __iomem *rng_regs = (void __iomem *) rng->priv;
    *data = in_le32(rng_regs + PPC4XX_TRNG_DATA);
    return 4;
}

static int ppc4xx_rng_enable(int enable)
{
    struct device_node *ctrl;
    void __iomem *ctrl_reg;
    int err = 0;
    u32 val;

    /* Find the main crypto device node and map it to turn the TRNG on */
    ctrl = of_find_compatible_node(NULL, NULL, "amcc,ppc4xx-crypto");
    if (!ctrl)
        return -ENODEV;

    ctrl_reg = of_iomap(ctrl, 0);
    if (!ctrl_reg) {
        err = -ENODEV;
        goto out;
    }

    val = in_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL);

    if (enable)
        val |= PPC4XX_TRNGE;
    else
        val = val & ~PPC4XX_TRNGE;

    out_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL, val);
    iounmap(ctrl_reg);

out:
    of_node_put(ctrl);

    return err;
}

static struct hwrng ppc4xx_rng = {
    .name = MODULE_NAME,
    .data_present = ppc4xx_rng_data_present,
    .data_read = ppc4xx_rng_data_read,
};

static int __devinit ppc4xx_rng_probe(struct platform_device *dev)
{
    void __iomem *rng_regs;
    int err = 0;

    rng_regs = of_iomap(dev->dev.of_node, 0);
    if (!rng_regs)
        return -ENODEV;

    err = ppc4xx_rng_enable(1);
    if (err)
        return err;

    out_le32(rng_regs + PPC4XX_TRNG_CTRL, PPC4XX_TRNG_CTRL_DALM);
    ppc4xx_rng.priv = (unsigned long) rng_regs;

    err = hwrng_register(&ppc4xx_rng);

    return err;
}

static int __devexit ppc4xx_rng_remove(struct platform_device *dev)
{
    void __iomem *rng_regs = (void __iomem *) ppc4xx_rng.priv;

    hwrng_unregister(&ppc4xx_rng);
    ppc4xx_rng_enable(0);
    iounmap(rng_regs);

    return 0;
}

static struct of_device_id ppc4xx_rng_match[] = {
    { .compatible = "ppc4xx-rng", },
    { .compatible = "amcc,ppc460ex-rng", },
    { .compatible = "amcc,ppc440epx-rng", },
    {},
};

static struct platform_driver ppc4xx_rng_driver = {
    .driver = {
        .name = MODULE_NAME,
        .owner = THIS_MODULE,
        .of_match_table = ppc4xx_rng_match,
    },
    .probe = ppc4xx_rng_probe,
    .remove = ppc4xx_rng_remove,
};

module_platform_driver(ppc4xx_rng_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Josh Boyer <[email protected]>");
MODULE_DESCRIPTION("HW RNG driver for PPC 4xx processors");