/*
 * RNG driver for Intel 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/hw_random.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/stop_machine.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <asm/io.h>


#define PFX	KBUILD_MODNAME ": "

/*
 * RNG registers
 */
#define INTEL_RNG_HW_STATUS			0
#define         INTEL_RNG_PRESENT		0x40
#define         INTEL_RNG_ENABLED		0x01
#define INTEL_RNG_STATUS			1
#define         INTEL_RNG_DATA_PRESENT		0x01
#define INTEL_RNG_DATA				2

/*
 * Magic address at which Intel PCI bridges locate the RNG
 */
#define INTEL_RNG_ADDR				0xFFBC015F
#define INTEL_RNG_ADDR_LEN			3

/*
 * LPC bridge PCI config space registers
 */
#define FWH_DEC_EN1_REG_OLD			0xe3
#define FWH_DEC_EN1_REG_NEW			0xd9 /* high byte of 16-bit register */
#define FWH_F8_EN_MASK				0x80

#define BIOS_CNTL_REG_OLD			0x4e
#define BIOS_CNTL_REG_NEW			0xdc
#define BIOS_CNTL_WRITE_ENABLE_MASK		0x01
#define BIOS_CNTL_LOCK_ENABLE_MASK		0x02

/*
 * Magic address at which Intel Firmware Hubs get accessed
 */
#define INTEL_FWH_ADDR				0xffff0000
#define INTEL_FWH_ADDR_LEN			2

/*
 * Intel Firmware Hub command codes (write to any address inside the device)
 */
#define INTEL_FWH_RESET_CMD			0xff /* aka READ_ARRAY */
#define INTEL_FWH_READ_ID_CMD			0x90

/*
 * Intel Firmware Hub Read ID command result addresses
 */
#define INTEL_FWH_MANUFACTURER_CODE_ADDRESS	0x000000
#define INTEL_FWH_DEVICE_CODE_ADDRESS		0x000001

/*
 * Intel Firmware Hub Read ID command result values
 */
#define INTEL_FWH_MANUFACTURER_CODE		0x89
#define INTEL_FWH_DEVICE_CODE_8M		0xac
#define INTEL_FWH_DEVICE_CODE_4M		0xad

/*
 * 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[] = {
/* AA
	{ PCI_DEVICE(0x8086, 0x2418) }, */
	{ PCI_DEVICE(0x8086, 0x2410) }, /* AA */
/* AB
	{ PCI_DEVICE(0x8086, 0x2428) }, */
	{ PCI_DEVICE(0x8086, 0x2420) }, /* AB */
/* ??
	{ PCI_DEVICE(0x8086, 0x2430) }, */
/* BAM, CAM, DBM, FBM, GxM
	{ PCI_DEVICE(0x8086, 0x2448) }, */
	{ PCI_DEVICE(0x8086, 0x244c) }, /* BAM */
	{ PCI_DEVICE(0x8086, 0x248c) }, /* CAM */
	{ PCI_DEVICE(0x8086, 0x24cc) }, /* DBM */
	{ PCI_DEVICE(0x8086, 0x2641) }, /* FBM */
	{ PCI_DEVICE(0x8086, 0x27b9) }, /* GxM */
	{ PCI_DEVICE(0x8086, 0x27bd) }, /* GxM DH */
/* BA, CA, DB, Ex, 6300, Fx, 631x/632x, Gx
	{ PCI_DEVICE(0x8086, 0x244e) }, */
	{ PCI_DEVICE(0x8086, 0x2440) }, /* BA */
	{ PCI_DEVICE(0x8086, 0x2480) }, /* CA */
	{ PCI_DEVICE(0x8086, 0x24c0) }, /* DB */
	{ PCI_DEVICE(0x8086, 0x24d0) }, /* Ex */
	{ PCI_DEVICE(0x8086, 0x25a1) }, /* 6300 */
	{ PCI_DEVICE(0x8086, 0x2640) }, /* Fx */
	{ PCI_DEVICE(0x8086, 0x2670) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2671) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2672) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2673) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2674) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2675) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2676) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2677) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2678) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x2679) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267a) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267b) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267c) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267d) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267e) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x267f) }, /* 631x/632x */
	{ PCI_DEVICE(0x8086, 0x27b8) }, /* Gx */
/* E
	{ PCI_DEVICE(0x8086, 0x245e) }, */
	{ PCI_DEVICE(0x8086, 0x2450) }, /* E  */
	{ 0, },	/* terminate list */
};
MODULE_DEVICE_TABLE(pci, pci_tbl);

static __initdata int no_fwh_detect;
module_param(no_fwh_detect, int, 0);
MODULE_PARM_DESC(no_fwh_detect, "Skip FWH detection:\n"
                                " positive value - skip if FWH space locked read-only\n"
                                " negative value - skip always");

static inline u8 hwstatus_get(void __iomem *mem)
{
	return readb(mem + INTEL_RNG_HW_STATUS);
}

static inline u8 hwstatus_set(void __iomem *mem,
			      u8 hw_status)
{
	writeb(hw_status, mem + INTEL_RNG_HW_STATUS);
	return hwstatus_get(mem);
}

static int intel_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 = !!(readb(mem + INTEL_RNG_STATUS) &
			  INTEL_RNG_DATA_PRESENT);
		if (data || !wait)
			break;
		udelay(10);
	}
	return data;
}

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

	*data = readb(mem + INTEL_RNG_DATA);

	return 1;
}

static int intel_rng_init(struct hwrng *rng)
{
	void __iomem *mem = (void __iomem *)rng->priv;
	u8 hw_status;
	int err = -EIO;

	hw_status = hwstatus_get(mem);
	/* turn RNG h/w on, if it's off */
	if ((hw_status & INTEL_RNG_ENABLED) == 0)
		hw_status = hwstatus_set(mem, hw_status | INTEL_RNG_ENABLED);
	if ((hw_status & INTEL_RNG_ENABLED) == 0) {
		pr_err(PFX "cannot enable RNG, aborting\n");
		goto out;
	}
	err = 0;
out:
	return err;
}

static void intel_rng_cleanup(struct hwrng *rng)
{
	void __iomem *mem = (void __iomem *)rng->priv;
	u8 hw_status;

	hw_status = hwstatus_get(mem);
	if (hw_status & INTEL_RNG_ENABLED)
		hwstatus_set(mem, hw_status & ~INTEL_RNG_ENABLED);
	else
		pr_warn(PFX "unusual: RNG already disabled\n");
}


static struct hwrng intel_rng = {
	.name		= "intel",
	.init		= intel_rng_init,
	.cleanup	= intel_rng_cleanup,
	.data_present	= intel_rng_data_present,
	.data_read	= intel_rng_data_read,
};

struct intel_rng_hw {
	struct pci_dev *dev;
	void __iomem *mem;
	u8 bios_cntl_off;
	u8 bios_cntl_val;
	u8 fwh_dec_en1_off;
	u8 fwh_dec_en1_val;
};

static int __init intel_rng_hw_init(void *_intel_rng_hw)
{
	struct intel_rng_hw *intel_rng_hw = _intel_rng_hw;
	u8 mfc, dvc;

	/* interrupts disabled in stop_machine call */

	if (!(intel_rng_hw->fwh_dec_en1_val & FWH_F8_EN_MASK))
		pci_write_config_byte(intel_rng_hw->dev,
		                      intel_rng_hw->fwh_dec_en1_off,
		                      intel_rng_hw->fwh_dec_en1_val |
				      FWH_F8_EN_MASK);
	if (!(intel_rng_hw->bios_cntl_val & BIOS_CNTL_WRITE_ENABLE_MASK))
		pci_write_config_byte(intel_rng_hw->dev,
		                      intel_rng_hw->bios_cntl_off,
		                      intel_rng_hw->bios_cntl_val |
				      BIOS_CNTL_WRITE_ENABLE_MASK);

	writeb(INTEL_FWH_RESET_CMD, intel_rng_hw->mem);
	writeb(INTEL_FWH_READ_ID_CMD, intel_rng_hw->mem);
	mfc = readb(intel_rng_hw->mem + INTEL_FWH_MANUFACTURER_CODE_ADDRESS);
	dvc = readb(intel_rng_hw->mem + INTEL_FWH_DEVICE_CODE_ADDRESS);
	writeb(INTEL_FWH_RESET_CMD, intel_rng_hw->mem);

	if (!(intel_rng_hw->bios_cntl_val &
	      (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK)))
		pci_write_config_byte(intel_rng_hw->dev,
				      intel_rng_hw->bios_cntl_off,
				      intel_rng_hw->bios_cntl_val);
	if (!(intel_rng_hw->fwh_dec_en1_val & FWH_F8_EN_MASK))
		pci_write_config_byte(intel_rng_hw->dev,
				      intel_rng_hw->fwh_dec_en1_off,
				      intel_rng_hw->fwh_dec_en1_val);

	if (mfc != INTEL_FWH_MANUFACTURER_CODE ||
	    (dvc != INTEL_FWH_DEVICE_CODE_8M &&
	     dvc != INTEL_FWH_DEVICE_CODE_4M)) {
		pr_notice(PFX "FWH not detected\n");
		return -ENODEV;
	}

	return 0;
}

static int __init intel_init_hw_struct(struct intel_rng_hw *intel_rng_hw,
					struct pci_dev *dev)
{
	intel_rng_hw->bios_cntl_val = 0xff;
	intel_rng_hw->fwh_dec_en1_val = 0xff;
	intel_rng_hw->dev = dev;

	/* Check for Intel 82802 */
	if (dev->device < 0x2640) {
		intel_rng_hw->fwh_dec_en1_off = FWH_DEC_EN1_REG_OLD;
		intel_rng_hw->bios_cntl_off = BIOS_CNTL_REG_OLD;
	} else {
		intel_rng_hw->fwh_dec_en1_off = FWH_DEC_EN1_REG_NEW;
		intel_rng_hw->bios_cntl_off = BIOS_CNTL_REG_NEW;
	}

	pci_read_config_byte(dev, intel_rng_hw->fwh_dec_en1_off,
			     &intel_rng_hw->fwh_dec_en1_val);
	pci_read_config_byte(dev, intel_rng_hw->bios_cntl_off,
			     &intel_rng_hw->bios_cntl_val);

	if ((intel_rng_hw->bios_cntl_val &
	     (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK))
	    == BIOS_CNTL_LOCK_ENABLE_MASK) {
		static __initdata /*const*/ char warning[] =
PFX "Firmware space is locked read-only. If you can't or\n"
PFX "don't want to disable this in firmware setup, and if\n"
PFX "you are certain that your system has a functional\n"
PFX "RNG, try using the 'no_fwh_detect' option.\n";

		if (no_fwh_detect)
			return -ENODEV;
		pr_warn("%s", warning);
		return -EBUSY;
	}

	intel_rng_hw->mem = ioremap_nocache(INTEL_FWH_ADDR, INTEL_FWH_ADDR_LEN);
	if (intel_rng_hw->mem == NULL)
		return -EBUSY;

	return 0;
}


static int __init mod_init(void)
{
	int err = -ENODEV;
	int i;
	struct pci_dev *dev = NULL;
	void __iomem *mem = mem;
	u8 hw_status;
	struct intel_rng_hw *intel_rng_hw;

	for (i = 0; !dev && pci_tbl[i].vendor; ++i)
		dev = pci_get_device(pci_tbl[i].vendor, pci_tbl[i].device,
				     NULL);

	if (!dev)
		goto out; /* Device not found. */

	if (no_fwh_detect < 0) {
		pci_dev_put(dev);
		goto fwh_done;
	}

	intel_rng_hw = kmalloc(sizeof(*intel_rng_hw), GFP_KERNEL);
	if (!intel_rng_hw) {
		pci_dev_put(dev);
		goto out;
	}

	err = intel_init_hw_struct(intel_rng_hw, dev);
	if (err) {
		pci_dev_put(dev);
		kfree(intel_rng_hw);
		if (err == -ENODEV)
			goto fwh_done;
		goto out;
	}

	/*
	 * Since the BIOS code/data is going to disappear from its normal
	 * location with the Read ID command, all activity on the system
	 * must be stopped until the state is back to normal.
	 *
	 * Use stop_machine because IPIs can be blocked by disabling
	 * interrupts.
	 */
	err = stop_machine(intel_rng_hw_init, intel_rng_hw, NULL);
	pci_dev_put(dev);
	iounmap(intel_rng_hw->mem);
	kfree(intel_rng_hw);
	if (err)
		goto out;

fwh_done:
	err = -ENOMEM;
	mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
	if (!mem)
		goto out;
	intel_rng.priv = (unsigned long)mem;

	/* Check for Random Number Generator */
	err = -ENODEV;
	hw_status = hwstatus_get(mem);
	if ((hw_status & INTEL_RNG_PRESENT) == 0) {
		iounmap(mem);
		goto out;
	}

	pr_info("Intel 82802 RNG detected\n");
	err = hwrng_register(&intel_rng);
	if (err) {
		pr_err(PFX "RNG registering failed (%d)\n",
		       err);
		iounmap(mem);
	}
out:
	return err;

}

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

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

module_init(mod_init);
module_exit(mod_exit);

MODULE_DESCRIPTION("H/W RNG driver for Intel chipsets");
MODULE_LICENSE("GPL");