amd-rng.c

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/*
 * RNG driver for AMD 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 ": "


/*
 * 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, 0x7443), 0, },
    { PCI_VDEVICE(AMD, 0x746b), 0, },
    { 0, }, /* terminate list */
};
MODULE_DEVICE_TABLE(pci, pci_tbl);

static struct pci_dev *amd_pdev;


static int amd_rng_data_present(struct hwrng *rng, int wait)
{
    u32 pmbase = (u32)rng->priv;
    int data, i;

    for (i = 0; i < 20; i++) {
        data = !!(inl(pmbase + 0xF4) & 1);
        if (data || !wait)
            break;
        udelay(10);
    }
    return data;
}

static int amd_rng_data_read(struct hwrng *rng, u32 *data)
{
    u32 pmbase = (u32)rng->priv;

    *data = inl(pmbase + 0xF0);

    return 4;
}

static int amd_rng_init(struct hwrng *rng)
{
    u8 rnen;

    pci_read_config_byte(amd_pdev, 0x40, &rnen);
    rnen |= (1 << 7);   /* RNG on */
    pci_write_config_byte(amd_pdev, 0x40, rnen);

    pci_read_config_byte(amd_pdev, 0x41, &rnen);
    rnen |= (1 << 7);   /* PMIO enable */
    pci_write_config_byte(amd_pdev, 0x41, rnen);

    return 0;
}

static void amd_rng_cleanup(struct hwrng *rng)
{
    u8 rnen;

    pci_read_config_byte(amd_pdev, 0x40, &rnen);
    rnen &= ~(1 << 7);  /* RNG off */
    pci_write_config_byte(amd_pdev, 0x40, rnen);
}


static struct hwrng amd_rng = {
    .name       = "amd",
    .init       = amd_rng_init,
    .cleanup    = amd_rng_cleanup,
    .data_present   = amd_rng_data_present,
    .data_read  = amd_rng_data_read,
};


static int __init mod_init(void)
{
    int err = -ENODEV;
    struct pci_dev *pdev = NULL;
    const struct pci_device_id *ent;
    u32 pmbase;

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

found:
    err = pci_read_config_dword(pdev, 0x58, &pmbase);
    if (err)
        goto out;
    err = -EIO;
    pmbase &= 0x0000FF00;
    if (pmbase == 0)
        goto out;
    if (!request_region(pmbase + 0xF0, 8, "AMD HWRNG")) {
        dev_err(&pdev->dev, "AMD HWRNG region 0x%x already in use!\n",
            pmbase + 0xF0);
        err = -EBUSY;
        goto out;
    }
    amd_rng.priv = (unsigned long)pmbase;
    amd_pdev = pdev;

    printk(KERN_INFO "AMD768 RNG detected\n");
    err = hwrng_register(&amd_rng);
    if (err) {
        printk(KERN_ERR PFX "RNG registering failed (%d)\n",
               err);
        release_region(pmbase + 0xF0, 8);
        goto out;
    }
out:
    return err;
}

static void __exit mod_exit(void)
{
    u32 pmbase = (unsigned long)amd_rng.priv;
    release_region(pmbase + 0xF0, 8);
    hwrng_unregister(&amd_rng);
}

module_init(mod_init);
module_exit(mod_exit);

MODULE_AUTHOR("The Linux Kernel team");
MODULE_DESCRIPTION("H/W RNG driver for AMD chipsets");
MODULE_LICENSE("GPL");