/***************************************************************************
 *   Copyright (C) 2010-2011 Hans de Goede <hdegoede@redhat.com>           *
 *                                                                         *
 *   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; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/acpi.h>
#include <linux/delay.h>
#include "sch56xx-common.h"

#define SIO_SCH56XX_LD_EM	0x0C	/* Embedded uController Logical Dev */
#define SIO_UNLOCK_KEY		0x55	/* Key to enable Super-I/O */
#define SIO_LOCK_KEY		0xAA	/* Key to disable Super-I/O */

#define SIO_REG_LDSEL		0x07	/* Logical device select */
#define SIO_REG_DEVID		0x20	/* Device ID */
#define SIO_REG_ENABLE		0x30	/* Logical device enable */
#define SIO_REG_ADDR		0x66	/* Logical device address (2 bytes) */

#define SIO_SCH5627_ID		0xC6	/* Chipset ID */
#define SIO_SCH5636_ID		0xC7	/* Chipset ID */

#define REGION_LENGTH		9

#define SCH56XX_CMD_READ	0x02
#define SCH56XX_CMD_WRITE	0x03

static struct platform_device *sch56xx_pdev;

/* Super I/O functions */
static inline int superio_inb(int base, int reg)
{
	outb(reg, base);
	return inb(base + 1);
}

static inline int superio_enter(int base)
{
	/* Don't step on other drivers' I/O space by accident */
	if (!request_muxed_region(base, 2, "sch56xx")) {
		pr_err("I/O address 0x%04x already in use\n", base);
		return -EBUSY;
	}

	outb(SIO_UNLOCK_KEY, base);

	return 0;
}

static inline void superio_select(int base, int ld)
{
	outb(SIO_REG_LDSEL, base);
	outb(ld, base + 1);
}

static inline void superio_exit(int base)
{
	outb(SIO_LOCK_KEY, base);
	release_region(base, 2);
}

static int sch56xx_send_cmd(u16 addr, u8 cmd, u16 reg, u8 v)
{
	u8 val;
	int i;
	/*
	 * According to SMSC for the commands we use the maximum time for
	 * the EM to respond is 15 ms, but testing shows in practice it
	 * responds within 15-32 reads, so we first busy poll, and if
	 * that fails sleep a bit and try again until we are way past
	 * the 15 ms maximum response time.
	 */
	const int max_busy_polls = 64;
	const int max_lazy_polls = 32;

	/* (Optional) Write-Clear the EC to Host Mailbox Register */
	val = inb(addr + 1);
	outb(val, addr + 1);

	/* Set Mailbox Address Pointer to first location in Region 1 */
	outb(0x00, addr + 2);
	outb(0x80, addr + 3);

	/* Write Request Packet Header */
	outb(cmd, addr + 4); /* VREG Access Type read:0x02 write:0x03 */
	outb(0x01, addr + 5); /* # of Entries: 1 Byte (8-bit) */
	outb(0x04, addr + 2); /* Mailbox AP to first data entry loc. */

	/* Write Value field */
	if (cmd == SCH56XX_CMD_WRITE)
		outb(v, addr + 4);

	/* Write Address field */
	outb(reg & 0xff, addr + 6);
	outb(reg >> 8, addr + 7);

	/* Execute the Random Access Command */
	outb(0x01, addr); /* Write 01h to the Host-to-EC register */

	/* EM Interface Polling "Algorithm" */
	for (i = 0; i < max_busy_polls + max_lazy_polls; i++) {
		if (i >= max_busy_polls)
			msleep(1);
		/* Read Interrupt source Register */
		val = inb(addr + 8);
		/* Write Clear the interrupt source bits */
		if (val)
			outb(val, addr + 8);
		/* Command Completed ? */
		if (val & 0x01)
			break;
	}
	if (i == max_busy_polls + max_lazy_polls) {
		pr_err("Max retries exceeded reading virtual "
		       "register 0x%04hx (%d)\n", reg, 1);
		return -EIO;
	}

	/*
	 * According to SMSC we may need to retry this, but sofar I've always
	 * seen this succeed in 1 try.
	 */
	for (i = 0; i < max_busy_polls; i++) {
		/* Read EC-to-Host Register */
		val = inb(addr + 1);
		/* Command Completed ? */
		if (val == 0x01)
			break;

		if (i == 0)
			pr_warn("EC reports: 0x%02x reading virtual register "
				"0x%04hx\n", (unsigned int)val, reg);
	}
	if (i == max_busy_polls) {
		pr_err("Max retries exceeded reading virtual "
		       "register 0x%04hx (%d)\n", reg, 2);
		return -EIO;
	}

	/*
	 * According to the SMSC app note we should now do:
	 *
	 * Set Mailbox Address Pointer to first location in Region 1 *
	 * outb(0x00, addr + 2);
	 * outb(0x80, addr + 3);
	 *
	 * But if we do that things don't work, so let's not.
	 */

	/* Read Value field */
	if (cmd == SCH56XX_CMD_READ)
		return inb(addr + 4);

	return 0;
}

int sch56xx_read_virtual_reg(u16 addr, u16 reg)
{
	return sch56xx_send_cmd(addr, SCH56XX_CMD_READ, reg, 0);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg);

int sch56xx_write_virtual_reg(u16 addr, u16 reg, u8 val)
{
	return sch56xx_send_cmd(addr, SCH56XX_CMD_WRITE, reg, val);
}
EXPORT_SYMBOL(sch56xx_write_virtual_reg);

int sch56xx_read_virtual_reg16(u16 addr, u16 reg)
{
	int lsb, msb;

	/* Read LSB first, this will cause the matching MSB to be latched */
	lsb = sch56xx_read_virtual_reg(addr, reg);
	if (lsb < 0)
		return lsb;

	msb = sch56xx_read_virtual_reg(addr, reg + 1);
	if (msb < 0)
		return msb;

	return lsb | (msb << 8);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg16);

int sch56xx_read_virtual_reg12(u16 addr, u16 msb_reg, u16 lsn_reg,
			       int high_nibble)
{
	int msb, lsn;

	/* Read MSB first, this will cause the matching LSN to be latched */
	msb = sch56xx_read_virtual_reg(addr, msb_reg);
	if (msb < 0)
		return msb;

	lsn = sch56xx_read_virtual_reg(addr, lsn_reg);
	if (lsn < 0)
		return lsn;

	if (high_nibble)
		return (msb << 4) | (lsn >> 4);
	else
		return (msb << 4) | (lsn & 0x0f);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg12);

static int __init sch56xx_find(int sioaddr, unsigned short *address,
			       const char **name)
{
	u8 devid;
	int err;

	err = superio_enter(sioaddr);
	if (err)
		return err;

	devid = superio_inb(sioaddr, SIO_REG_DEVID);
	switch (devid) {
	case SIO_SCH5627_ID:
		*name = "sch5627";
		break;
	case SIO_SCH5636_ID:
		*name = "sch5636";
		break;
	default:
		pr_debug("Unsupported device id: 0x%02x\n",
			 (unsigned int)devid);
		err = -ENODEV;
		goto exit;
	}

	superio_select(sioaddr, SIO_SCH56XX_LD_EM);

	if (!(superio_inb(sioaddr, SIO_REG_ENABLE) & 0x01)) {
		pr_warn("Device not activated\n");
		err = -ENODEV;
		goto exit;
	}

	/*
	 * Warning the order of the low / high byte is the other way around
	 * as on most other superio devices!!
	 */
	*address = superio_inb(sioaddr, SIO_REG_ADDR) |
		   superio_inb(sioaddr, SIO_REG_ADDR + 1) << 8;
	if (*address == 0) {
		pr_warn("Base address not set\n");
		err = -ENODEV;
		goto exit;
	}

exit:
	superio_exit(sioaddr);
	return err;
}

static int __init sch56xx_device_add(unsigned short address, const char *name)
{
	struct resource res = {
		.start	= address,
		.end	= address + REGION_LENGTH - 1,
		.flags	= IORESOURCE_IO,
	};
	int err;

	sch56xx_pdev = platform_device_alloc(name, address);
	if (!sch56xx_pdev)
		return -ENOMEM;

	res.name = sch56xx_pdev->name;
	err = acpi_check_resource_conflict(&res);
	if (err)
		goto exit_device_put;

	err = platform_device_add_resources(sch56xx_pdev, &res, 1);
	if (err) {
		pr_err("Device resource addition failed\n");
		goto exit_device_put;
	}

	err = platform_device_add(sch56xx_pdev);
	if (err) {
		pr_err("Device addition failed\n");
		goto exit_device_put;
	}

	return 0;

exit_device_put:
	platform_device_put(sch56xx_pdev);

	return err;
}

static int __init sch56xx_init(void)
{
	int err;
	unsigned short address;
	const char *name;

	err = sch56xx_find(0x4e, &address, &name);
	if (err)
		err = sch56xx_find(0x2e, &address, &name);
	if (err)
		return err;

	return sch56xx_device_add(address, name);
}

static void __exit sch56xx_exit(void)
{
	platform_device_unregister(sch56xx_pdev);
}

MODULE_DESCRIPTION("SMSC SCH56xx Hardware Monitoring Common Code");
MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
MODULE_LICENSE("GPL");

module_init(sch56xx_init);
module_exit(sch56xx_exit);