text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * An rtc driver for the Dallas DS1553
   *
   * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
   */
  
  #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		0x2000
  #define RTC_OFFSET		0x1ff0
  
  #define RTC_FLAGS		(RTC_OFFSET + 0)
  #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_CONTROL		(RTC_OFFSET + 8)
  #define RTC_CENTURY		(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_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 Flags register */
  #define RTC_FLAGS_AF		0x40
  #define RTC_FLAGS_BLF		0x10
  
  /* Bits in the Interrupts register */
  #define RTC_INTS_AE		0x80
  
  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 ds1553_rtc_set_time(struct device *dev, struct rtc_time *tm)
  {
  	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	u8 century;
  
  	century = bin2bcd((tm->tm_year + 1900) / 100);
  
  	writeb(RTC_WRITE, pdata->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 ds1553_rtc_read_time(struct device *dev, struct rtc_time *tm)
  {
  	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  	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;
  
  	return 0;
  }
  
  static void ds1553_rtc_update_alarm(struct rtc_plat_data *pdata)
  {
  	void __iomem *ioaddr = pdata->ioaddr;
  	unsigned long flags;
  
  	spin_lock_irqsave(&pdata->lock, 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_AE : 0, ioaddr + RTC_INTERRUPTS);
  	readb(ioaddr + RTC_FLAGS);	/* clear interrupts */
  	spin_unlock_irqrestore(&pdata->lock, flags);
  }
  
  static int ds1553_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  
  	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;
  	ds1553_rtc_update_alarm(pdata);
  	return 0;
  }
  
  static int ds1553_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
  {
  	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  
  	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 ds1553_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 ds1553_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
  {
  	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
  
  	if (pdata->irq <= 0)
  		return -EINVAL;
  	if (enabled)
  		pdata->irqen |= RTC_AF;
  	else
  		pdata->irqen &= ~RTC_AF;
  	ds1553_rtc_update_alarm(pdata);
  	return 0;
  }
  
  static const struct rtc_class_ops ds1553_rtc_ops = {
  	.read_time		= ds1553_rtc_read_time,
  	.set_time		= ds1553_rtc_set_time,
  	.read_alarm		= ds1553_rtc_read_alarm,
  	.set_alarm		= ds1553_rtc_set_alarm,
  	.alarm_irq_enable	= ds1553_rtc_alarm_irq_enable,
  };
  
  static int ds1553_nvram_read(void *priv, unsigned int pos, void *val,
  			     size_t bytes)
  {
  	struct platform_device *pdev = priv;
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	u8 *buf = val;
  
  	for (; bytes; bytes--)
  		*buf++ = readb(ioaddr + pos++);
  	return 0;
  }
  
  static int ds1553_nvram_write(void *priv, unsigned int pos, void *val,
  			      size_t bytes)
  {
  	struct platform_device *pdev = priv;
  	struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
  	void __iomem *ioaddr = pdata->ioaddr;
  	u8 *buf = val;
  
  	for (; bytes; bytes--)
  		writeb(*buf++, ioaddr + pos++);
  	return 0;
  }
  
  static int ds1553_rtc_probe(struct platform_device *pdev)
  {
  	unsigned int cen, sec;
  	struct rtc_plat_data *pdata;
  	void __iomem *ioaddr;
  	int ret = 0;
  	struct nvmem_config nvmem_cfg = {
  		.name = "ds1553_nvram",
  		.word_size = 1,
  		.stride = 1,
  		.size = RTC_OFFSET,
  		.reg_read = ds1553_nvram_read,
  		.reg_write = ds1553_nvram_write,
  		.priv = pdev,
  	};
  
  	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
  	if (!pdata)
  		return -ENOMEM;
  
  	ioaddr = devm_platform_ioremap_resource(pdev, 0);
  	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 */
  	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_FLAGS) & RTC_FLAGS_BLF)
  		dev_warn(&pdev->dev, "voltage-low detected.\n");
  
  	spin_lock_init(&pdata->lock);
  	pdata->last_jiffies = jiffies;
  	platform_set_drvdata(pdev, pdata);
  
  	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
  	if (IS_ERR(pdata->rtc))
  		return PTR_ERR(pdata->rtc);
  
  	pdata->rtc->ops = &ds1553_rtc_ops;
  	pdata->rtc->nvram_old_abi = true;
  
  	ret = rtc_register_device(pdata->rtc);
  	if (ret)
  		return ret;
  
  	if (pdata->irq > 0) {
  		writeb(0, ioaddr + RTC_INTERRUPTS);
  		if (devm_request_irq(&pdev->dev, pdata->irq,
  				ds1553_rtc_interrupt,
  				0, pdev->name, pdev) < 0) {
  			dev_warn(&pdev->dev, "interrupt not available.\n");
  			pdata->irq = 0;
  		}
  	}
  
  	if (rtc_nvmem_register(pdata->rtc, &nvmem_cfg))
  		dev_err(&pdev->dev, "unable to register nvmem\n");
  
  	return 0;
  }
  
  /* work with hotplug and coldplug */
  MODULE_ALIAS("platform:rtc-ds1553");
  
  static struct platform_driver ds1553_rtc_driver = {
  	.probe		= ds1553_rtc_probe,
  	.driver		= {
  		.name	= "rtc-ds1553",
  	},
  };
  
  module_platform_driver(ds1553_rtc_driver);
  
  MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
  MODULE_DESCRIPTION("Dallas DS1553 RTC driver");
  MODULE_LICENSE("GPL");
  