/*
 * 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 <jgarzik@redhat.com>
 *
 * 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 <jgarzik@pobox.com>
 * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
 *
 * 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/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>

#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)
{
	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) {
			rng_base = pci_resource_start(pdev, 0);
			if (rng_base == 0)
				return -ENODEV;

			mem = devm_ioremap(&pdev->dev, rng_base, 0x58);
			if (!mem)
				return -ENOMEM;
			geode_rng.priv = (unsigned long)mem;

			pr_info("AMD Geode RNG detected\n");
			return devm_hwrng_register(&pdev->dev, &geode_rng);
		}
	}

	/* Device not found. */
	return -ENODEV;
}

static void __exit mod_exit(void)
{
}

module_init(mod_init);
module_exit(mod_exit);

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