/*
 * An rtc driver for the Dallas DS1742
 *
 * Copyright (C) 2006 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/delay.h>
#include <linux/jiffies.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/io.h>

#define DRV_VERSION "0.1"

#define RTC_REG_SIZE		0x800
#define RTC_OFFSET		0x7f8

#define RTC_CONTROL		(RTC_OFFSET + 0)
#define RTC_CENTURY		(RTC_OFFSET + 0)
#define RTC_SECONDS		(RTC_OFFSET + 1)
#define RTC_MINUTES		(RTC_OFFSET + 2)
#define RTC_HOURS		(RTC_OFFSET + 3)
#define RTC_DAY			(RTC_OFFSET + 4)
#define RTC_DATE		(RTC_OFFSET + 5)
#define RTC_MONTH		(RTC_OFFSET + 6)
#define RTC_YEAR		(RTC_OFFSET + 7)

#define RTC_CENTURY_MASK	0x3f
#define RTC_SECONDS_MASK	0x7f
#define RTC_DAY_MASK		0x07

/* Bits in the Control/Century register */
#define RTC_WRITE		0x80
#define RTC_READ		0x40

/* Bits in the Seconds register */
#define RTC_STOP		0x80

/* Bits in the Day register */
#define RTC_BATT_FLAG		0x80

struct rtc_plat_data {
	struct rtc_device *rtc;
	void __iomem *ioaddr;
	unsigned long baseaddr;
	unsigned long last_jiffies;
};

static int ds1742_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 century;

	century = BIN2BCD((tm->tm_year + 1900) / 100);

	writeb(RTC_WRITE, ioaddr + RTC_CONTROL);

	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);

	/* RTC_CENTURY and RTC_CONTROL share same register */
	writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
	writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
	return 0;
}

static int ds1742_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;

	/* give enough time to update RTC in case of continuous read */
	if (pdata->last_jiffies == jiffies)
		msleep(1);
	pdata->last_jiffies = jiffies;
	writeb(RTC_READ, ioaddr + RTC_CONTROL);
	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) & RTC_CENTURY_MASK;
	writeb(0, ioaddr + RTC_CONTROL);
	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.\n");
		rtc_time_to_tm(0, tm);
	}
	return 0;
}

static struct rtc_class_ops ds1742_rtc_ops = {
	.read_time	= ds1742_rtc_read_time,
	.set_time	= ds1742_rtc_set_time,
};

static ssize_t ds1742_nvram_read(struct kobject *kobj, char *buf,
				 loff_t pos, size_t size)
{
	struct platform_device *pdev =
		to_platform_device(container_of(kobj, struct device, kobj));
	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
	void __iomem *ioaddr = pdata->ioaddr;
	ssize_t count;

	for (count = 0; size > 0 && pos < RTC_OFFSET; count++, size--)
		*buf++ = readb(ioaddr + pos++);
	return count;
}

static ssize_t ds1742_nvram_write(struct kobject *kobj, char *buf,
				  loff_t pos, size_t size)
{
	struct platform_device *pdev =
		to_platform_device(container_of(kobj, struct device, kobj));
	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
	void __iomem *ioaddr = pdata->ioaddr;
	ssize_t count;

	for (count = 0; size > 0 && pos < RTC_OFFSET; count++, size--)
		writeb(*buf++, ioaddr + pos++);
	return count;
}

static struct bin_attribute ds1742_nvram_attr = {
	.attr = {
		.name = "nvram",
		.mode = S_IRUGO | S_IWUGO,
		.owner = THIS_MODULE,
	},
	.size = RTC_OFFSET,
	.read = ds1742_nvram_read,
	.write = ds1742_nvram_write,
};

static int __init ds1742_rtc_probe(struct platform_device *pdev)
{
	struct rtc_device *rtc;
	struct resource *res;
	unsigned int cen, sec;
	struct rtc_plat_data *pdata = NULL;
	void __iomem *ioaddr = NULL;
	int ret = 0;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENODEV;
	pdata = kzalloc(sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
		return -ENOMEM;
	if (!request_mem_region(res->start, RTC_REG_SIZE, pdev->name)) {
		ret = -EBUSY;
		goto out;
	}
	pdata->baseaddr = res->start;
	ioaddr = ioremap(pdata->baseaddr, RTC_REG_SIZE);
	if (!ioaddr) {
		ret = -ENOMEM;
		goto out;
	}
	pdata->ioaddr = ioaddr;

	/* turn RTC on if it was not on */
	sec = readb(ioaddr + RTC_SECONDS);
	if (sec & RTC_STOP) {
		sec &= RTC_SECONDS_MASK;
		cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
		writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
		writeb(sec, ioaddr + RTC_SECONDS);
		writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
	}
	if (readb(ioaddr + RTC_DAY) & RTC_BATT_FLAG)
		dev_warn(&pdev->dev, "voltage-low detected.\n");

	rtc = rtc_device_register(pdev->name, &pdev->dev,
				  &ds1742_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc)) {
		ret = PTR_ERR(rtc);
		goto out;
	}
	pdata->rtc = rtc;
	pdata->last_jiffies = jiffies;
	platform_set_drvdata(pdev, pdata);
	sysfs_create_bin_file(&pdev->dev.kobj, &ds1742_nvram_attr);
	return 0;
 out:
	if (ioaddr)
		iounmap(ioaddr);
	if (pdata->baseaddr)
		release_mem_region(pdata->baseaddr, RTC_REG_SIZE);
	kfree(pdata);
	return ret;
}

static int __devexit ds1742_rtc_remove(struct platform_device *pdev)
{
	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);

	sysfs_remove_bin_file(&pdev->dev.kobj, &ds1742_nvram_attr);
	rtc_device_unregister(pdata->rtc);
	iounmap(pdata->ioaddr);
	release_mem_region(pdata->baseaddr, RTC_REG_SIZE);
	kfree(pdata);
	return 0;
}

static struct platform_driver ds1742_rtc_driver = {
	.probe		= ds1742_rtc_probe,
	.remove		= __devexit_p(ds1742_rtc_remove),
	.driver		= {
		.name	= "ds1742",
		.owner	= THIS_MODULE,
	},
};

static __init int ds1742_init(void)
{
	return platform_driver_register(&ds1742_rtc_driver);
}

static __exit void ds1742_exit(void)
{
	return platform_driver_unregister(&ds1742_rtc_driver);
}

module_init(ds1742_init);
module_exit(ds1742_exit);

MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);