/***************************************************************************
   *   Copyright (C) 2010-2012 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 <linux/fs.h>
  #include <linux/watchdog.h>
  #include <linux/miscdevice.h>
  #include <linux/uaccess.h>
  #include <linux/kref.h>
  #include <linux/slab.h>
  #include "sch56xx-common.h"
  
  /* Insmod parameters */
  static int nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, int, 0);
  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  #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		10
  
  #define SCH56XX_CMD_READ	0x02
  #define SCH56XX_CMD_WRITE	0x03
  
  /* Watchdog registers */
  #define SCH56XX_REG_WDOG_PRESET		0x58B
  #define SCH56XX_REG_WDOG_CONTROL	0x58C
  #define SCH56XX_WDOG_TIME_BASE_SEC	0x01
  #define SCH56XX_REG_WDOG_OUTPUT_ENABLE	0x58E
  #define SCH56XX_WDOG_OUTPUT_ENABLE	0x02
  
  struct sch56xx_watchdog_data {
  	u16 addr;
  	struct mutex *io_lock;
  	struct kref kref;
  	struct watchdog_info wdinfo;
  	struct watchdog_device wddev;
  	u8 watchdog_preset;
  	u8 watchdog_control;
  	u8 watchdog_output_enable;
  };
  
  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
  ", 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)
  ",
  		       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
  ",
  				(unsigned int)val, reg);
  	}
  	if (i == max_busy_polls) {
  		pr_err("Max retries exceeded reading virtual register 0x%04hx (%d)
  ",
  		       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);
  
  /*
   * Watchdog routines
   */
  
  /* Release our data struct when we're unregistered *and*
     all references to our watchdog device are released */
  static void watchdog_release_resources(struct kref *r)
  {
  	struct sch56xx_watchdog_data *data =
  		container_of(r, struct sch56xx_watchdog_data, kref);
  	kfree(data);
  }
  
  static int watchdog_set_timeout(struct watchdog_device *wddev,
  				unsigned int timeout)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  	unsigned int resolution;
  	u8 control;
  	int ret;
  
  	/* 1 second or 60 second resolution? */
  	if (timeout <= 255)
  		resolution = 1;
  	else
  		resolution = 60;
  
  	if (timeout < resolution || timeout > (resolution * 255))
  		return -EINVAL;
  
  	if (resolution == 1)
  		control = data->watchdog_control | SCH56XX_WDOG_TIME_BASE_SEC;
  	else
  		control = data->watchdog_control & ~SCH56XX_WDOG_TIME_BASE_SEC;
  
  	if (data->watchdog_control != control) {
  		mutex_lock(data->io_lock);
  		ret = sch56xx_write_virtual_reg(data->addr,
  						SCH56XX_REG_WDOG_CONTROL,
  						control);
  		mutex_unlock(data->io_lock);
  		if (ret)
  			return ret;
  
  		data->watchdog_control = control;
  	}
  
  	/*
  	 * Remember new timeout value, but do not write as that (re)starts
  	 * the watchdog countdown.
  	 */
  	data->watchdog_preset = DIV_ROUND_UP(timeout, resolution);
  	wddev->timeout = data->watchdog_preset * resolution;
  
  	return 0;
  }
  
  static int watchdog_start(struct watchdog_device *wddev)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  	int ret;
  	u8 val;
  
  	/*
  	 * The sch56xx's watchdog cannot really be started / stopped
  	 * it is always running, but we can avoid the timer expiring
  	 * from causing a system reset by clearing the output enable bit.
  	 *
  	 * The sch56xx's watchdog will set the watchdog event bit, bit 0
  	 * of the second interrupt source register (at base-address + 9),
  	 * when the timer expires.
  	 *
  	 * This will only cause a system reset if the 0-1 flank happens when
  	 * output enable is true. Setting output enable after the flank will
  	 * not cause a reset, nor will the timer expiring a second time.
  	 * This means we must clear the watchdog event bit in case it is set.
  	 *
  	 * The timer may still be running (after a recent watchdog_stop) and
  	 * mere milliseconds away from expiring, so the timer must be reset
  	 * first!
  	 */
  
  	mutex_lock(data->io_lock);
  
  	/* 1. Reset the watchdog countdown counter */
  	ret = sch56xx_write_virtual_reg(data->addr, SCH56XX_REG_WDOG_PRESET,
  					data->watchdog_preset);
  	if (ret)
  		goto leave;
  
  	/* 2. Enable output */
  	val = data->watchdog_output_enable | SCH56XX_WDOG_OUTPUT_ENABLE;
  	ret = sch56xx_write_virtual_reg(data->addr,
  					SCH56XX_REG_WDOG_OUTPUT_ENABLE, val);
  	if (ret)
  		goto leave;
  
  	data->watchdog_output_enable = val;
  
  	/* 3. Clear the watchdog event bit if set */
  	val = inb(data->addr + 9);
  	if (val & 0x01)
  		outb(0x01, data->addr + 9);
  
  leave:
  	mutex_unlock(data->io_lock);
  	return ret;
  }
  
  static int watchdog_trigger(struct watchdog_device *wddev)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  	int ret;
  
  	/* Reset the watchdog countdown counter */
  	mutex_lock(data->io_lock);
  	ret = sch56xx_write_virtual_reg(data->addr, SCH56XX_REG_WDOG_PRESET,
  					data->watchdog_preset);
  	mutex_unlock(data->io_lock);
  
  	return ret;
  }
  
  static int watchdog_stop(struct watchdog_device *wddev)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  	int ret = 0;
  	u8 val;
  
  	val = data->watchdog_output_enable & ~SCH56XX_WDOG_OUTPUT_ENABLE;
  	mutex_lock(data->io_lock);
  	ret = sch56xx_write_virtual_reg(data->addr,
  					SCH56XX_REG_WDOG_OUTPUT_ENABLE, val);
  	mutex_unlock(data->io_lock);
  	if (ret)
  		return ret;
  
  	data->watchdog_output_enable = val;
  	return 0;
  }
  
  static void watchdog_ref(struct watchdog_device *wddev)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  
  	kref_get(&data->kref);
  }
  
  static void watchdog_unref(struct watchdog_device *wddev)
  {
  	struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
  
  	kref_put(&data->kref, watchdog_release_resources);
  }
  
  static const struct watchdog_ops watchdog_ops = {
  	.owner		= THIS_MODULE,
  	.start		= watchdog_start,
  	.stop		= watchdog_stop,
  	.ping		= watchdog_trigger,
  	.set_timeout	= watchdog_set_timeout,
  	.ref		= watchdog_ref,
  	.unref		= watchdog_unref,
  };
  
  struct sch56xx_watchdog_data *sch56xx_watchdog_register(struct device *parent,
  	u16 addr, u32 revision, struct mutex *io_lock, int check_enabled)
  {
  	struct sch56xx_watchdog_data *data;
  	int err, control, output_enable;
  
  	/* Cache the watchdog registers */
  	mutex_lock(io_lock);
  	control =
  		sch56xx_read_virtual_reg(addr, SCH56XX_REG_WDOG_CONTROL);
  	output_enable =
  		sch56xx_read_virtual_reg(addr, SCH56XX_REG_WDOG_OUTPUT_ENABLE);
  	mutex_unlock(io_lock);
  
  	if (control < 0)
  		return NULL;
  	if (output_enable < 0)
  		return NULL;
  	if (check_enabled && !(output_enable & SCH56XX_WDOG_OUTPUT_ENABLE)) {
  		pr_warn("Watchdog not enabled by BIOS, not registering
  ");
  		return NULL;
  	}
  
  	data = kzalloc(sizeof(struct sch56xx_watchdog_data), GFP_KERNEL);
  	if (!data)
  		return NULL;
  
  	data->addr = addr;
  	data->io_lock = io_lock;
  	kref_init(&data->kref);
  
  	strlcpy(data->wdinfo.identity, "sch56xx watchdog",
  		sizeof(data->wdinfo.identity));
  	data->wdinfo.firmware_version = revision;
  	data->wdinfo.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT;
  	if (!nowayout)
  		data->wdinfo.options |= WDIOF_MAGICCLOSE;
  
  	data->wddev.info = &data->wdinfo;
  	data->wddev.ops = &watchdog_ops;
  	data->wddev.parent = parent;
  	data->wddev.timeout = 60;
  	data->wddev.min_timeout = 1;
  	data->wddev.max_timeout = 255 * 60;
  	if (nowayout)
  		set_bit(WDOG_NO_WAY_OUT, &data->wddev.status);
  	if (output_enable & SCH56XX_WDOG_OUTPUT_ENABLE)
  		set_bit(WDOG_ACTIVE, &data->wddev.status);
  
  	/* Since the watchdog uses a downcounter there is no register to read
  	   the BIOS set timeout from (if any was set at all) ->
  	   Choose a preset which will give us a 1 minute timeout */
  	if (control & SCH56XX_WDOG_TIME_BASE_SEC)
  		data->watchdog_preset = 60; /* seconds */
  	else
  		data->watchdog_preset = 1; /* minute */
  
  	data->watchdog_control = control;
  	data->watchdog_output_enable = output_enable;
  
  	watchdog_set_drvdata(&data->wddev, data);
  	err = watchdog_register_device(&data->wddev);
  	if (err) {
  		pr_err("Registering watchdog chardev: %d
  ", err);
  		kfree(data);
  		return NULL;
  	}
  
  	return data;
  }
  EXPORT_SYMBOL(sch56xx_watchdog_register);
  
  void sch56xx_watchdog_unregister(struct sch56xx_watchdog_data *data)
  {
  	watchdog_unregister_device(&data->wddev);
  	kref_put(&data->kref, watchdog_release_resources);
  	/* Don't touch data after this it may have been free-ed! */
  }
  EXPORT_SYMBOL(sch56xx_watchdog_unregister);
  
  /*
   * platform dev find, add and remove functions
   */
  
  static int __init sch56xx_find(int sioaddr, const char **name)
  {
  	u8 devid;
  	unsigned short address;
  	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
  ",
  			 (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
  ");
  		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
  ");
  		err = -ENODEV;
  		goto exit;
  	}
  	err = address;
  
  exit:
  	superio_exit(sioaddr);
  	return err;
  }
  
  static int __init sch56xx_device_add(int 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
  ");
  		goto exit_device_put;
  	}
  
  	err = platform_device_add(sch56xx_pdev);
  	if (err) {
  		pr_err("Device addition failed
  ");
  		goto exit_device_put;
  	}
  
  	return 0;
  
  exit_device_put:
  	platform_device_put(sch56xx_pdev);
  
  	return err;
  }
  
  static int __init sch56xx_init(void)
  {
  	int address;
  	const char *name = NULL;
  
  	address = sch56xx_find(0x4e, &name);
  	if (address < 0)
  		address = sch56xx_find(0x2e, &name);
  	if (address < 0)
  		return address;
  
  	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);