geode-rng.c

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/*
 * RNG driver for AMD Geode RNGs
 *
 * Copyright 2005 (c) MontaVista Software, Inc.
 *
 * with the majority of the code coming from:
 *
 * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
 * (c) Copyright 2003 Red Hat Inc <[email protected]>
 *
 * derived from
 *
 * Hardware driver for the AMD 768 Random Number Generator (RNG)
 * (c) Copyright 2001 Red Hat Inc
 *
 * derived from
 *
 * Hardware driver for Intel i810 Random Number Generator (RNG)
 * Copyright 2000,2001 Jeff Garzik <[email protected]>
 * Copyright 2000,2001 Philipp Rumpf <[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/kernel.h>
#include <linux/pci.h>
#include <linux/hw_random.h>
#include <linux/delay.h>
#include <asm/io.h>


#define PFX KBUILD_MODNAME ": "

#define GEODE_RNG_DATA_REG   0x50
#define GEODE_RNG_STATUS_REG 0x54

/*
 * Data for PCI driver interface
 *
 * This data only exists for exporting the supported
 * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
 * register a pci_driver, because someone else might one day
 * want to register another driver on the same PCI id.
 */
static const struct pci_device_id pci_tbl[] = {
    { PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_LX_AES), 0, },
    { 0, }, /* terminate list */
};
MODULE_DEVICE_TABLE(pci, pci_tbl);


static int geode_rng_data_read(struct hwrng *rng, u32 *data)
{
    void __iomem *mem = (void __iomem *)rng->priv;

    *data = readl(mem + GEODE_RNG_DATA_REG);

    return 4;
}

static int geode_rng_data_present(struct hwrng *rng, int wait)
{
    void __iomem *mem = (void __iomem *)rng->priv;
    int data, i;

    for (i = 0; i < 20; i++) {
        data = !!(readl(mem + GEODE_RNG_STATUS_REG));
        if (data || !wait)
            break;
        udelay(10);
    }
    return data;
}


static struct hwrng geode_rng = {
    .name       = "geode",
    .data_present   = geode_rng_data_present,
    .data_read  = geode_rng_data_read,
};


static int __init mod_init(void)
{
    int err = -ENODEV;
    struct pci_dev *pdev = NULL;
    const struct pci_device_id *ent;
    void __iomem *mem;
    unsigned long rng_base;

    for_each_pci_dev(pdev) {
        ent = pci_match_id(pci_tbl, pdev);
        if (ent)
            goto found;
    }
    /* Device not found. */
    goto out;

found:
    rng_base = pci_resource_start(pdev, 0);
    if (rng_base == 0)
        goto out;
    err = -ENOMEM;
    mem = ioremap(rng_base, 0x58);
    if (!mem)
        goto out;
    geode_rng.priv = (unsigned long)mem;

    printk(KERN_INFO "AMD Geode RNG detected\n");
    err = hwrng_register(&geode_rng);
    if (err) {
        printk(KERN_ERR PFX "RNG registering failed (%d)\n",
               err);
        goto err_unmap;
    }
out:
    return err;

err_unmap:
    iounmap(mem);
    goto out;
}

static void __exit mod_exit(void)
{
    void __iomem *mem = (void __iomem *)geode_rng.priv;

    hwrng_unregister(&geode_rng);
    iounmap(mem);
}

module_init(mod_init);
module_exit(mod_exit);

MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
MODULE_LICENSE("GPL");