/*
   * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
   *
   * Copyright (C) 2000 Silicon Graphics, Inc.
   * Written by Ulf Carlsson (ulfc@engr.sgi.com)
   *
   * Copyright (C) 2008 Thomas Bogendoerfer
   *
   * Based on code written by Paul Gortmaker.
   *
   * 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.
   */
  
  #include <linux/module.h>
  #include <linux/rtc.h>
  #include <linux/slab.h>
  #include <linux/platform_device.h>
  #include <linux/bcd.h>
  #include <linux/io.h>
  #include <linux/err.h>
  
  #define DRV_VERSION		"1.0"
  
  struct m48t35_rtc {
  	u8	pad[0x7ff8];    /* starts at 0x7ff8 */
  	u8	control;
  	u8	sec;
  	u8	min;
  	u8	hour;
  	u8	day;
  	u8	date;
  	u8	month;
  	u8	year;
  };
  
  #define M48T35_RTC_SET		0x80
  #define M48T35_RTC_READ		0x40
  
  struct m48t35_priv {
  	struct rtc_device *rtc;
  	struct m48t35_rtc __iomem *reg;
  	size_t size;
  	unsigned long baseaddr;
  	spinlock_t lock;
  };
  
  static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct m48t35_priv *priv = dev_get_drvdata(dev);
  	u8 control;
  
  	/*
  	 * Only the values that we read from the RTC are set. We leave
  	 * tm_wday, tm_yday and tm_isdst untouched. Even though the
  	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  	 * by the RTC when initially set to a non-zero value.
  	 */
  	spin_lock_irq(&priv->lock);
  	control = readb(&priv->reg->control);
  	writeb(control | M48T35_RTC_READ, &priv->reg->control);
  	tm->tm_sec = readb(&priv->reg->sec);
  	tm->tm_min = readb(&priv->reg->min);
  	tm->tm_hour = readb(&priv->reg->hour);
  	tm->tm_mday = readb(&priv->reg->date);
  	tm->tm_mon = readb(&priv->reg->month);
  	tm->tm_year = readb(&priv->reg->year);
  	writeb(control, &priv->reg->control);
  	spin_unlock_irq(&priv->lock);
  
  	tm->tm_sec = bcd2bin(tm->tm_sec);
  	tm->tm_min = bcd2bin(tm->tm_min);
  	tm->tm_hour = bcd2bin(tm->tm_hour);
  	tm->tm_mday = bcd2bin(tm->tm_mday);
  	tm->tm_mon = bcd2bin(tm->tm_mon);
  	tm->tm_year = bcd2bin(tm->tm_year);
  
  	/*
  	 * Account for differences between how the RTC uses the values
  	 * and how they are defined in a struct rtc_time;
  	 */
  	tm->tm_year += 70;
  	if (tm->tm_year <= 69)
  		tm->tm_year += 100;
  
  	tm->tm_mon--;
  	return rtc_valid_tm(tm);
  }
  
  static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct m48t35_priv *priv = dev_get_drvdata(dev);
  	unsigned char mon, day, hrs, min, sec;
  	unsigned int yrs;
  	u8 control;
  
  	yrs = tm->tm_year + 1900;
  	mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
  	day = tm->tm_mday;
  	hrs = tm->tm_hour;
  	min = tm->tm_min;
  	sec = tm->tm_sec;
  
  	if (yrs < 1970)
  		return -EINVAL;
  
  	yrs -= 1970;
  	if (yrs > 255)    /* They are unsigned */
  		return -EINVAL;
  
  	if (yrs > 169)
  		return -EINVAL;
  
  	if (yrs >= 100)
  		yrs -= 100;
  
  	sec = bin2bcd(sec);
  	min = bin2bcd(min);
  	hrs = bin2bcd(hrs);
  	day = bin2bcd(day);
  	mon = bin2bcd(mon);
  	yrs = bin2bcd(yrs);
  
  	spin_lock_irq(&priv->lock);
  	control = readb(&priv->reg->control);
  	writeb(control | M48T35_RTC_SET, &priv->reg->control);
  	writeb(yrs, &priv->reg->year);
  	writeb(mon, &priv->reg->month);
  	writeb(day, &priv->reg->date);
  	writeb(hrs, &priv->reg->hour);
  	writeb(min, &priv->reg->min);
  	writeb(sec, &priv->reg->sec);
  	writeb(control, &priv->reg->control);
  	spin_unlock_irq(&priv->lock);
  	return 0;
  }
  
  static const struct rtc_class_ops m48t35_ops = {
  	.read_time	= m48t35_read_time,
  	.set_time	= m48t35_set_time,
  };
  
  static int m48t35_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	struct m48t35_priv *priv;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!res)
  		return -ENODEV;
  	priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	priv->size = resource_size(res);
  	/*
  	 * kludge: remove the #ifndef after ioc3 resource
  	 * conflicts are resolved
  	 */
  #ifndef CONFIG_SGI_IP27
  	if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
  				     pdev->name))
  		return -EBUSY;
  #endif
  	priv->baseaddr = res->start;
  	priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
  	if (!priv->reg)
  		return -ENOMEM;
  
  	spin_lock_init(&priv->lock);
  
  	platform_set_drvdata(pdev, priv);
  
  	priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
  				  &m48t35_ops, THIS_MODULE);
  	return PTR_ERR_OR_ZERO(priv->rtc);
  }
  
  static struct platform_driver m48t35_platform_driver = {
  	.driver		= {
  		.name	= "rtc-m48t35",
  		.owner	= THIS_MODULE,
  	},
  	.probe		= m48t35_probe,
  };
  
  module_platform_driver(m48t35_platform_driver);
  
  MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
  MODULE_DESCRIPTION("M48T35 RTC driver");
  MODULE_LICENSE("GPL");
  MODULE_VERSION(DRV_VERSION);
  MODULE_ALIAS("platform:rtc-m48t35");