/*
   * A RTC driver for the Simtek STK17TA8
   *

   * By Thomas Hommel <thomas.hommel@ge.com>

   *
   * Based on the DS1553 driver from
   * Atsushi Nemoto <anemo@mba.ocn.ne.jp>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/bcd.h>
  #include <linux/init.h>
  #include <linux/kernel.h>

  #include <linux/gfp.h>

  #include <linux/delay.h>
  #include <linux/jiffies.h>
  #include <linux/interrupt.h>
  #include <linux/rtc.h>
  #include <linux/platform_device.h>
  #include <linux/io.h>

  #include <linux/module.h>

  #define RTC_REG_SIZE		0x20000
  #define RTC_OFFSET		0x1fff0
  
  #define RTC_FLAGS		(RTC_OFFSET + 0)
  #define RTC_CENTURY		(RTC_OFFSET + 1)
  #define RTC_SECONDS_ALARM	(RTC_OFFSET + 2)
  #define RTC_MINUTES_ALARM	(RTC_OFFSET + 3)
  #define RTC_HOURS_ALARM		(RTC_OFFSET + 4)
  #define RTC_DATE_ALARM		(RTC_OFFSET + 5)
  #define RTC_INTERRUPTS		(RTC_OFFSET + 6)
  #define RTC_WATCHDOG		(RTC_OFFSET + 7)
  #define RTC_CALIBRATION		(RTC_OFFSET + 8)
  #define RTC_SECONDS		(RTC_OFFSET + 9)
  #define RTC_MINUTES		(RTC_OFFSET + 10)
  #define RTC_HOURS		(RTC_OFFSET + 11)
  #define RTC_DAY			(RTC_OFFSET + 12)
  #define RTC_DATE		(RTC_OFFSET + 13)
  #define RTC_MONTH		(RTC_OFFSET + 14)
  #define RTC_YEAR		(RTC_OFFSET + 15)
  
  #define RTC_SECONDS_MASK	0x7f
  #define RTC_DAY_MASK		0x07
  #define RTC_CAL_MASK		0x3f
  
  /* Bits in the Calibration register */
  #define RTC_STOP		0x80
  
  /* Bits in the Flags register */
  #define RTC_FLAGS_AF		0x40
  #define RTC_FLAGS_PF		0x20
  #define RTC_WRITE		0x02
  #define RTC_READ		0x01
  
  /* Bits in the Interrupts register */
  #define RTC_INTS_AIE		0x40
  
  struct rtc_plat_data {
  	struct rtc_device *rtc;
  	void __iomem *ioaddr;

  	unsigned long last_jiffies;
  	int irq;
  	unsigned int irqen;
  	int alrm_sec;
  	int alrm_min;
  	int alrm_hour;
  	int alrm_mday;

  	spinlock_t lock;

  };
  
  static int stk17ta8_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	u8 flags;
  
  	flags = readb(pdata->ioaddr + RTC_FLAGS);
  	writeb(flags | RTC_WRITE, pdata->ioaddr + RTC_FLAGS);

  	writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
  	writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
  	writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
  	writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
  	writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
  	writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
  	writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
  	writeb(bin2bcd((tm->tm_year + 1900) / 100), ioaddr + RTC_CENTURY);

  
  	writeb(flags & ~RTC_WRITE, pdata->ioaddr + RTC_FLAGS);
  	return 0;
  }
  
  static int stk17ta8_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	unsigned int year, month, day, hour, minute, second, week;
  	unsigned int century;
  	u8 flags;
  
  	/* give enough time to update RTC in case of continuous read */
  	if (pdata->last_jiffies == jiffies)
  		msleep(1);
  	pdata->last_jiffies = jiffies;
  
  	flags = readb(pdata->ioaddr + RTC_FLAGS);
  	writeb(flags | RTC_READ, ioaddr + RTC_FLAGS);
  	second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
  	minute = readb(ioaddr + RTC_MINUTES);
  	hour = readb(ioaddr + RTC_HOURS);
  	day = readb(ioaddr + RTC_DATE);
  	week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
  	month = readb(ioaddr + RTC_MONTH);
  	year = readb(ioaddr + RTC_YEAR);
  	century = readb(ioaddr + RTC_CENTURY);
  	writeb(flags & ~RTC_READ, ioaddr + RTC_FLAGS);

  	tm->tm_sec = bcd2bin(second);
  	tm->tm_min = bcd2bin(minute);
  	tm->tm_hour = bcd2bin(hour);
  	tm->tm_mday = bcd2bin(day);
  	tm->tm_wday = bcd2bin(week);
  	tm->tm_mon = bcd2bin(month) - 1;

  	/* year is 1900 + tm->tm_year */

  	tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;

  
  	if (rtc_valid_tm(tm) < 0) {
  		dev_err(dev, "retrieved date/time is not valid.
  ");
  		rtc_time_to_tm(0, tm);
  	}
  	return 0;
  }
  
  static void stk17ta8_rtc_update_alarm(struct rtc_plat_data *pdata)
  {
  	void __iomem *ioaddr = pdata->ioaddr;
  	unsigned long irqflags;
  	u8 flags;

  	spin_lock_irqsave(&pdata->lock, irqflags);

  
  	flags = readb(ioaddr + RTC_FLAGS);
  	writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);
  
  	writeb(pdata->alrm_mday < 0 || (pdata->irqen & RTC_UF) ?

  	       0x80 : bin2bcd(pdata->alrm_mday),

  	       ioaddr + RTC_DATE_ALARM);
  	writeb(pdata->alrm_hour < 0 || (pdata->irqen & RTC_UF) ?

  	       0x80 : bin2bcd(pdata->alrm_hour),

  	       ioaddr + RTC_HOURS_ALARM);
  	writeb(pdata->alrm_min < 0 || (pdata->irqen & RTC_UF) ?

  	       0x80 : bin2bcd(pdata->alrm_min),

  	       ioaddr + RTC_MINUTES_ALARM);
  	writeb(pdata->alrm_sec < 0 || (pdata->irqen & RTC_UF) ?

  	       0x80 : bin2bcd(pdata->alrm_sec),

  	       ioaddr + RTC_SECONDS_ALARM);
  	writeb(pdata->irqen ? RTC_INTS_AIE : 0, ioaddr + RTC_INTERRUPTS);
  	readb(ioaddr + RTC_FLAGS);	/* clear interrupts */
  	writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);

  	spin_unlock_irqrestore(&pdata->lock, irqflags);

  }
  
  static int stk17ta8_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);

  	if (pdata->irq <= 0)

  		return -EINVAL;
  	pdata->alrm_mday = alrm->time.tm_mday;
  	pdata->alrm_hour = alrm->time.tm_hour;
  	pdata->alrm_min = alrm->time.tm_min;
  	pdata->alrm_sec = alrm->time.tm_sec;
  	if (alrm->enabled)
  		pdata->irqen |= RTC_AF;
  	stk17ta8_rtc_update_alarm(pdata);
  	return 0;
  }
  
  static int stk17ta8_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);

  	if (pdata->irq <= 0)

  		return -EINVAL;
  	alrm->time.tm_mday = pdata->alrm_mday < 0 ? 0 : pdata->alrm_mday;
  	alrm->time.tm_hour = pdata->alrm_hour < 0 ? 0 : pdata->alrm_hour;
  	alrm->time.tm_min = pdata->alrm_min < 0 ? 0 : pdata->alrm_min;
  	alrm->time.tm_sec = pdata->alrm_sec < 0 ? 0 : pdata->alrm_sec;
  	alrm->enabled = (pdata->irqen & RTC_AF) ? 1 : 0;
  	return 0;
  }
  
  static irqreturn_t stk17ta8_rtc_interrupt(int irq, void *dev_id)
  {
  	struct platform_device *pdev = dev_id;
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;

  	unsigned long events = 0;

  	spin_lock(&pdata->lock);

  	/* read and clear interrupt */

  	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_AF) {
  		events = RTC_IRQF;
  		if (readb(ioaddr + RTC_SECONDS_ALARM) & 0x80)
  			events |= RTC_UF;
  		else
  			events |= RTC_AF;

  		rtc_update_irq(pdata->rtc, 1, events);

  	}
  	spin_unlock(&pdata->lock);
  	return events ? IRQ_HANDLED : IRQ_NONE;

  }

  static int stk17ta8_rtc_alarm_irq_enable(struct device *dev,
  	unsigned int enabled)

  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);

  	if (pdata->irq <= 0)

  		return -EINVAL;
  	if (enabled)

  		pdata->irqen |= RTC_AF;

  	else
  		pdata->irqen &= ~RTC_AF;
  	stk17ta8_rtc_update_alarm(pdata);

  	return 0;
  }
  
  static const struct rtc_class_ops stk17ta8_rtc_ops = {

  	.read_time		= stk17ta8_rtc_read_time,
  	.set_time		= stk17ta8_rtc_set_time,
  	.read_alarm		= stk17ta8_rtc_read_alarm,
  	.set_alarm		= stk17ta8_rtc_set_alarm,
  	.alarm_irq_enable	= stk17ta8_rtc_alarm_irq_enable,

  };

  static ssize_t stk17ta8_nvram_read(struct file *filp, struct kobject *kobj,

  				 struct bin_attribute *attr, char *buf,

  				 loff_t pos, size_t size)
  {

  	struct device *dev = container_of(kobj, struct device, kobj);
  	struct platform_device *pdev = to_platform_device(dev);

  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	ssize_t count;

  	for (count = 0; count < size; count++)

  		*buf++ = readb(ioaddr + pos++);
  	return count;
  }

  static ssize_t stk17ta8_nvram_write(struct file *filp, struct kobject *kobj,

  				  struct bin_attribute *attr, char *buf,

  				  loff_t pos, size_t size)
  {

  	struct device *dev = container_of(kobj, struct device, kobj);
  	struct platform_device *pdev = to_platform_device(dev);

  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	ssize_t count;

  	for (count = 0; count < size; count++)

  		writeb(*buf++, ioaddr + pos++);
  	return count;
  }
  
  static struct bin_attribute stk17ta8_nvram_attr = {
  	.attr = {
  		.name = "nvram",

  		.mode = S_IRUGO | S_IWUSR,

  	},
  	.size = RTC_OFFSET,
  	.read = stk17ta8_nvram_read,
  	.write = stk17ta8_nvram_write,
  };

  static int stk17ta8_rtc_probe(struct platform_device *pdev)

  {

  	struct resource *res;
  	unsigned int cal;
  	unsigned int flags;
  	struct rtc_plat_data *pdata;

  	void __iomem *ioaddr;

  	int ret = 0;

  	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);

  	if (!pdata)
  		return -ENOMEM;

  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	ioaddr = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(ioaddr))
  		return PTR_ERR(ioaddr);

  	pdata->ioaddr = ioaddr;
  	pdata->irq = platform_get_irq(pdev, 0);
  
  	/* turn RTC on if it was not on */
  	cal = readb(ioaddr + RTC_CALIBRATION);
  	if (cal & RTC_STOP) {
  		cal &= RTC_CAL_MASK;
  		flags = readb(ioaddr + RTC_FLAGS);
  		writeb(flags | RTC_WRITE, ioaddr + RTC_FLAGS);
  		writeb(cal, ioaddr + RTC_CALIBRATION);
  		writeb(flags & ~RTC_WRITE, ioaddr + RTC_FLAGS);
  	}
  	if (readb(ioaddr + RTC_FLAGS) & RTC_FLAGS_PF)
  		dev_warn(&pdev->dev, "voltage-low detected.
  ");

  	spin_lock_init(&pdata->lock);
  	pdata->last_jiffies = jiffies;
  	platform_set_drvdata(pdev, pdata);

  	if (pdata->irq > 0) {

  		writeb(0, ioaddr + RTC_INTERRUPTS);

  		if (devm_request_irq(&pdev->dev, pdata->irq,
  				stk17ta8_rtc_interrupt,

  				IRQF_SHARED,

  				pdev->name, pdev) < 0) {
  			dev_warn(&pdev->dev, "interrupt not available.
  ");

  			pdata->irq = 0;

  		}
  	}

  	pdata->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,

  				  &stk17ta8_rtc_ops, THIS_MODULE);

  	if (IS_ERR(pdata->rtc))
  		return PTR_ERR(pdata->rtc);

  	ret = sysfs_create_bin_file(&pdev->dev.kobj, &stk17ta8_nvram_attr);

  	return ret;
  }

  static int stk17ta8_rtc_remove(struct platform_device *pdev)

  {
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  
  	sysfs_remove_bin_file(&pdev->dev.kobj, &stk17ta8_nvram_attr);

  	if (pdata->irq > 0)

  		writeb(0, pdata->ioaddr + RTC_INTERRUPTS);

  	return 0;
  }

  /* work with hotplug and coldplug */
  MODULE_ALIAS("platform:stk17ta8");

  static struct platform_driver stk17ta8_rtc_driver = {
  	.probe		= stk17ta8_rtc_probe,

  	.remove		= stk17ta8_rtc_remove,

  	.driver		= {
  		.name	= "stk17ta8",

  	},
  };

  module_platform_driver(stk17ta8_rtc_driver);

  MODULE_AUTHOR("Thomas Hommel <thomas.hommel@ge.com>");

  MODULE_DESCRIPTION("Simtek STK17TA8 RTC driver");
  MODULE_LICENSE("GPL");