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pcf8563.c

/*
 * PCF8563 RTC
 *
 * From Phillips' datasheet:
 *
 * The PCF8563 is a CMOS real-time clock/calendar optimized for low power
 * consumption. A programmable clock output, interrupt output and voltage
 * low detector are also provided. All address and data are transferred
 * serially via two-line bidirectional I2C-bus. Maximum bus speed is
 * 400 kbits/s. The built-in word address register is incremented
 * automatically after each written or read byte.
 *
 * Copyright (c) 2002-2007, Axis Communications AB
 * All rights reserved.
 *
 * Author: Tobias Anderberg <tobiasa@axis.com>.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/delay.h>
#include <linux/bcd.h>
#include <linux/mutex.h>

#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/rtc.h>

#include "i2c.h"

#define PCF8563_MAJOR   121   /* Local major number. */
#define DEVICE_NAME     "rtc" /* Name which is registered in /proc/devices. */
#define PCF8563_NAME    "PCF8563"
#define DRIVER_VERSION  "$Revision: 1.17 $"

/* Two simple wrapper macros, saves a few keystrokes. */
#define rtc_read(x) i2c_readreg(RTC_I2C_READ, x)
#define rtc_write(x,y) i2c_writereg(RTC_I2C_WRITE, x, y)

static DEFINE_MUTEX(rtc_lock); /* Protect state etc */

static const unsigned char days_in_month[] =
      { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

int pcf8563_ioctl(struct inode *, struct file *, unsigned int, unsigned long);

/* Cache VL bit value read at driver init since writing the RTC_SECOND
 * register clears the VL status.
 */
static int voltage_low;

static const struct file_operations pcf8563_fops = {
      .owner =    THIS_MODULE,
      .ioctl =    pcf8563_ioctl
};

unsigned char
pcf8563_readreg(int reg)
{
      unsigned char res = rtc_read(reg);

      /* The PCF8563 does not return 0 for unimplemented bits. */
      switch (reg) {
            case RTC_SECONDS:
            case RTC_MINUTES:
                  res &= 0x7F;
                  break;
            case RTC_HOURS:
            case RTC_DAY_OF_MONTH:
                  res &= 0x3F;
                  break;
            case RTC_WEEKDAY:
                  res &= 0x07;
                  break;
            case RTC_MONTH:
                  res &= 0x1F;
                  break;
            case RTC_CONTROL1:
                  res &= 0xA8;
                  break;
            case RTC_CONTROL2:
                  res &= 0x1F;
                  break;
            case RTC_CLOCKOUT_FREQ:
            case RTC_TIMER_CONTROL:
                  res &= 0x83;
                  break;
      }
      return res;
}

void
pcf8563_writereg(int reg, unsigned char val)
{
      rtc_write(reg, val);
}

void
get_rtc_time(struct rtc_time *tm)
{
      tm->tm_sec  = rtc_read(RTC_SECONDS);
      tm->tm_min  = rtc_read(RTC_MINUTES);
      tm->tm_hour = rtc_read(RTC_HOURS);
      tm->tm_mday = rtc_read(RTC_DAY_OF_MONTH);
      tm->tm_wday = rtc_read(RTC_WEEKDAY);
      tm->tm_mon  = rtc_read(RTC_MONTH);
      tm->tm_year = rtc_read(RTC_YEAR);

      if (tm->tm_sec & 0x80) {
            printk(KERN_ERR "%s: RTC Voltage Low - reliable date/time "
                   "information is no longer guaranteed!\n", PCF8563_NAME);
      }

      tm->tm_year  = BCD_TO_BIN(tm->tm_year) +
                   ((tm->tm_mon & 0x80) ? 100 : 0);
      tm->tm_sec  &= 0x7F;
      tm->tm_min  &= 0x7F;
      tm->tm_hour &= 0x3F;
      tm->tm_mday &= 0x3F;
      tm->tm_wday &= 0x07; /* Not coded in BCD. */
      tm->tm_mon  &= 0x1F;

      BCD_TO_BIN(tm->tm_sec);
      BCD_TO_BIN(tm->tm_min);
      BCD_TO_BIN(tm->tm_hour);
      BCD_TO_BIN(tm->tm_mday);
      BCD_TO_BIN(tm->tm_mon);
      tm->tm_mon--; /* Month is 1..12 in RTC but 0..11 in linux */
}

int __init
pcf8563_init(void)
{
      static int res;
      static int first = 1;

      if (!first)
            return res;
      first = 0;

      /* Initiate the i2c protocol. */
      res = i2c_init();
      if (res < 0) {
            printk(KERN_CRIT "pcf8563_init: Failed to init i2c.\n");
            return res;
      }

      /*
       * First of all we need to reset the chip. This is done by
       * clearing control1, control2 and clk freq and resetting
       * all alarms.
       */
      if (rtc_write(RTC_CONTROL1, 0x00) < 0)
            goto err;

      if (rtc_write(RTC_CONTROL2, 0x00) < 0)
            goto err;

      if (rtc_write(RTC_CLOCKOUT_FREQ, 0x00) < 0)
            goto err;

      if (rtc_write(RTC_TIMER_CONTROL, 0x03) < 0)
            goto err;

      /* Reset the alarms. */
      if (rtc_write(RTC_MINUTE_ALARM, 0x80) < 0)
            goto err;

      if (rtc_write(RTC_HOUR_ALARM, 0x80) < 0)
            goto err;

      if (rtc_write(RTC_DAY_ALARM, 0x80) < 0)
            goto err;

      if (rtc_write(RTC_WEEKDAY_ALARM, 0x80) < 0)
            goto err;

      /* Check for low voltage, and warn about it. */
      if (rtc_read(RTC_SECONDS) & 0x80) {
            voltage_low = 1;
            printk(KERN_WARNING "%s: RTC Voltage Low - reliable "
                   "date/time information is no longer guaranteed!\n",
                   PCF8563_NAME);
      }

      return res;

err:
      printk(KERN_INFO "%s: Error initializing chip.\n", PCF8563_NAME);
      res = -1;
      return res;
}

void __exit
pcf8563_exit(void)
{
      unregister_chrdev(PCF8563_MAJOR, DEVICE_NAME);
}

/*
 * ioctl calls for this driver. Why return -ENOTTY upon error? Because
 * POSIX says so!
 */
int pcf8563_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
      unsigned long arg)
{
      /* Some sanity checks. */
      if (_IOC_TYPE(cmd) != RTC_MAGIC)
            return -ENOTTY;

      if (_IOC_NR(cmd) > RTC_MAX_IOCTL)
            return -ENOTTY;

      switch (cmd) {
      case RTC_RD_TIME:
      {
            struct rtc_time tm;

            mutex_lock(&rtc_lock);
            memset(&tm, 0, sizeof tm);
            get_rtc_time(&tm);

            if (copy_to_user((struct rtc_time *) arg, &tm,
                         sizeof tm)) {
                  mutex_unlock(&rtc_lock);
                  return -EFAULT;
            }

            mutex_unlock(&rtc_lock);

            return 0;
      }
      case RTC_SET_TIME:
      {
            int leap;
            int year;
            int century;
            struct rtc_time tm;

            memset(&tm, 0, sizeof tm);
            if (!capable(CAP_SYS_TIME))
                  return -EPERM;

            if (copy_from_user(&tm, (struct rtc_time *) arg,
                           sizeof tm))
                  return -EFAULT;

            /* Convert from struct tm to struct rtc_time. */
            tm.tm_year += 1900;
            tm.tm_mon += 1;

            /*
             * Check if tm.tm_year is a leap year. A year is a leap
             * year if it is divisible by 4 but not 100, except
             * that years divisible by 400 _are_ leap years.
             */
            year = tm.tm_year;
            leap = (tm.tm_mon == 2) &&
                  ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);

            /* Perform some sanity checks. */
            if ((tm.tm_year < 1970) ||
                (tm.tm_mon > 12) ||
                (tm.tm_mday == 0) ||
                (tm.tm_mday > days_in_month[tm.tm_mon] + leap) ||
                (tm.tm_wday >= 7) ||
                (tm.tm_hour >= 24) ||
                (tm.tm_min >= 60) ||
                (tm.tm_sec >= 60))
                  return -EINVAL;

            century = (tm.tm_year >= 2000) ? 0x80 : 0;
            tm.tm_year = tm.tm_year % 100;

            BIN_TO_BCD(tm.tm_year);
            BIN_TO_BCD(tm.tm_mon);
            BIN_TO_BCD(tm.tm_mday);
            BIN_TO_BCD(tm.tm_hour);
            BIN_TO_BCD(tm.tm_min);
            BIN_TO_BCD(tm.tm_sec);
            tm.tm_mon |= century;

            mutex_lock(&rtc_lock);

            rtc_write(RTC_YEAR, tm.tm_year);
            rtc_write(RTC_MONTH, tm.tm_mon);
            rtc_write(RTC_WEEKDAY, tm.tm_wday); /* Not coded in BCD. */
            rtc_write(RTC_DAY_OF_MONTH, tm.tm_mday);
            rtc_write(RTC_HOURS, tm.tm_hour);
            rtc_write(RTC_MINUTES, tm.tm_min);
            rtc_write(RTC_SECONDS, tm.tm_sec);

            mutex_unlock(&rtc_lock);

            return 0;
      }
      case RTC_VL_READ:
            if (voltage_low)
                  printk(KERN_ERR "%s: RTC Voltage Low - "
                         "reliable date/time information is no "
                         "longer guaranteed!\n", PCF8563_NAME);

            if (copy_to_user((int *) arg, &voltage_low, sizeof(int)))
                  return -EFAULT;
            return 0;

      case RTC_VL_CLR:
      {
            /* Clear the VL bit in the seconds register in case
             * the time has not been set already (which would
             * have cleared it). This does not really matter
             * because of the cached voltage_low value but do it
             * anyway for consistency. */

            int ret = rtc_read(RTC_SECONDS);

            rtc_write(RTC_SECONDS, (ret & 0x7F));

            /* Clear the cached value. */
            voltage_low = 0;

            return 0;
      }
      default:
            return -ENOTTY;
      }

      return 0;
}

static int __init pcf8563_register(void)
{
      if (pcf8563_init() < 0) {
            printk(KERN_INFO "%s: Unable to initialize Real-Time Clock "
                   "Driver, %s\n", PCF8563_NAME, DRIVER_VERSION);
            return -1;
      }

      if (register_chrdev(PCF8563_MAJOR, DEVICE_NAME, &pcf8563_fops) < 0) {
            printk(KERN_INFO "%s: Unable to get major numer %d for RTC "
                   "device.\n", PCF8563_NAME, PCF8563_MAJOR);
            return -1;
      }

      printk(KERN_INFO "%s Real-Time Clock Driver, %s\n", PCF8563_NAME,
             DRIVER_VERSION);

      /* Check for low voltage, and warn about it. */
      if (voltage_low) {
            printk(KERN_WARNING "%s: RTC Voltage Low - reliable date/time "
                   "information is no longer guaranteed!\n", PCF8563_NAME);
      }

      return 0;
}

module_init(pcf8563_register);
module_exit(pcf8563_exit);

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