/*
 *      Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
 *
 *      Real Time Clock interface for Linux
 *
 *      TODO: Implement periodic interrupts.
 *
 *      Copyright (C) 2000 Silicon Graphics, Inc.
 *      Written by Ulf Carlsson (ulfc@engr.sgi.com)
 *
 *      Based on code written by Paul Gortmaker.
 *
 *      This driver allows use of the real time clock (built into
 *      nearly all computers) from user space. It exports the /dev/rtc
 *      interface supporting various ioctl() and also the /proc/rtc
 *      pseudo-file for status information.
 *
 *      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.
 *
 */

#define RTC_VERSION             "1.09b"

#include <linux/bcd.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>

#include <asm/m48t35.h>
#include <asm/sn/ioc3.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/sn/klconfig.h>
#include <asm/sn/sn0/ip27.h>
#include <asm/sn/sn0/hub.h>
#include <asm/sn/sn_private.h>

static int rtc_ioctl(struct inode *inode, struct file *file,
                     unsigned int cmd, unsigned long arg);

static int rtc_read_proc(char *page, char **start, off_t off,
                         int count, int *eof, void *data);

static void get_rtc_time(struct rtc_time *rtc_tm);

/*
 *      Bits in rtc_status. (6 bits of room for future expansion)
 */

#define RTC_IS_OPEN             0x01    /* means /dev/rtc is in use     */
#define RTC_TIMER_ON            0x02    /* missed irq timer active      */

static unsigned char rtc_status;        /* bitmapped status byte.       */
static unsigned long rtc_freq;  /* Current periodic IRQ rate    */
static struct m48t35_rtc *rtc;

/*
 *      If this driver ever becomes modularised, it will be really nice
 *      to make the epoch retain its value across module reload...
 */

static unsigned long epoch = 1970;      /* year corresponding to 0x00   */

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

static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
                     unsigned long arg)
{

        struct rtc_time wtime;

        switch (cmd) {
        case RTC_RD_TIME:       /* Read the time/date from RTC  */
        {
                get_rtc_time(&wtime);
                break;
        }
        case RTC_SET_TIME:      /* Set the RTC */
        {
                struct rtc_time rtc_tm;
                unsigned char mon, day, hrs, min, sec, leap_yr;
                unsigned int yrs;

                if (!capable(CAP_SYS_TIME))
                        return -EACCES;

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

                yrs = rtc_tm.tm_year + 1900;
                mon = rtc_tm.tm_mon + 1;   /* tm_mon starts at zero */
                day = rtc_tm.tm_mday;
                hrs = rtc_tm.tm_hour;
                min = rtc_tm.tm_min;
                sec = rtc_tm.tm_sec;

                if (yrs < 1970)
                        return -EINVAL;

                leap_yr = ((!(yrs % 4) && (yrs % 100)) || !(yrs % 400));

                if ((mon > 12) || (day == 0))
                        return -EINVAL;

                if (day > (days_in_mo[mon] + ((mon == 2) && leap_yr)))
                        return -EINVAL;

                if ((hrs >= 24) || (min >= 60) || (sec >= 60))
                        return -EINVAL;

                if ((yrs -= epoch) > 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(&rtc_lock);
                rtc->control |= M48T35_RTC_SET;
                rtc->year = yrs;
                rtc->month = mon;
                rtc->date = day;
                rtc->hour = hrs;
                rtc->min = min;
                rtc->sec = sec;
                rtc->control &= ~M48T35_RTC_SET;
                spin_unlock_irq(&rtc_lock);

                return 0;
        }
        default:
                return -EINVAL;
        }
        return copy_to_user((void *)arg, &wtime, sizeof wtime) ? -EFAULT : 0;
}

/*
 *      We enforce only one user at a time here with the open/close.
 *      Also clear the previous interrupt data on an open, and clean
 *      up things on a close.
 */

static int rtc_open(struct inode *inode, struct file *file)
{
        spin_lock_irq(&rtc_lock);

        if (rtc_status & RTC_IS_OPEN) {
                spin_unlock_irq(&rtc_lock);
                return -EBUSY;
        }

        rtc_status |= RTC_IS_OPEN;
        spin_unlock_irq(&rtc_lock);

        return 0;
}

static int rtc_release(struct inode *inode, struct file *file)
{
        /*
         * Turn off all interrupts once the device is no longer
         * in use, and clear the data.
         */

        spin_lock_irq(&rtc_lock);
        rtc_status &= ~RTC_IS_OPEN;
        spin_unlock_irq(&rtc_lock);

        return 0;
}

/*
 *      The various file operations we support.
 */

static const struct file_operations rtc_fops = {
        .owner          = THIS_MODULE,
        .ioctl          = rtc_ioctl,
        .open           = rtc_open,
        .release        = rtc_release,
};

static struct miscdevice rtc_dev=
{
        RTC_MINOR,
        "rtc",
        &rtc_fops
};

static int __init rtc_init(void)
{
        rtc = (struct m48t35_rtc *)
        (KL_CONFIG_CH_CONS_INFO(master_nasid)->memory_base + IOC3_BYTEBUS_DEV0);

        printk(KERN_INFO "Real Time Clock Driver v%s\n", RTC_VERSION);
        if (misc_register(&rtc_dev)) {
                printk(KERN_ERR "rtc: cannot register misc device.\n");
                return -ENODEV;
        }
        if (!create_proc_read_entry("driver/rtc", 0, NULL, rtc_read_proc, NULL)) {
                printk(KERN_ERR "rtc: cannot create /proc/rtc.\n");
                misc_deregister(&rtc_dev);
                return -ENOENT;
        }

        rtc_freq = 1024;

        return 0;
}

static void __exit rtc_exit (void)
{
        /* interrupts and timer disabled at this point by rtc_release */

        remove_proc_entry ("rtc", NULL);
        misc_deregister(&rtc_dev);
}

module_init(rtc_init);
module_exit(rtc_exit);

/*
 *      Info exported via "/proc/rtc".
 */

static int rtc_get_status(char *buf)
{
        char *p;
        struct rtc_time tm;

        /*
         * Just emulate the standard /proc/rtc
         */

        p = buf;

        get_rtc_time(&tm);

        /*
         * There is no way to tell if the luser has the RTC set for local
         * time or for Universal Standard Time (GMT). Probably local though.
         */
        p += sprintf(p,
                     "rtc_time\t: %02d:%02d:%02d\n"
                     "rtc_date\t: %04d-%02d-%02d\n"
                     "rtc_epoch\t: %04lu\n"
                     "24hr\t\t: yes\n",
                     tm.tm_hour, tm.tm_min, tm.tm_sec,
                     tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, epoch);

        return  p - buf;
}

static int rtc_read_proc(char *page, char **start, off_t off,
                                 int count, int *eof, void *data)
{
        int len = rtc_get_status(page);
        if (len <= off+count) *eof = 1;
        *start = page + off;
        len -= off;
        if (len>count) len = count;
        if (len<0) len = 0;
        return len;
}

static void get_rtc_time(struct rtc_time *rtc_tm)
{
        /*
         * Do we need to wait for the last update to finish?
         */

        /*
         * 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(&rtc_lock);
        rtc->control |= M48T35_RTC_READ;
        rtc_tm->tm_sec = rtc->sec;
        rtc_tm->tm_min = rtc->min;
        rtc_tm->tm_hour = rtc->hour;
        rtc_tm->tm_mday = rtc->date;
        rtc_tm->tm_mon = rtc->month;
        rtc_tm->tm_year = rtc->year;
        rtc->control &= ~M48T35_RTC_READ;
        spin_unlock_irq(&rtc_lock);

        rtc_tm->tm_sec = BCD2BIN(rtc_tm->tm_sec);
        rtc_tm->tm_min = BCD2BIN(rtc_tm->tm_min);
        rtc_tm->tm_hour = BCD2BIN(rtc_tm->tm_hour);
        rtc_tm->tm_mday = BCD2BIN(rtc_tm->tm_mday);
        rtc_tm->tm_mon = BCD2BIN(rtc_tm->tm_mon);
        rtc_tm->tm_year = BCD2BIN(rtc_tm->tm_year);

        /*
         * Account for differences between how the RTC uses the values
         * and how they are defined in a struct rtc_time;
         */
        if ((rtc_tm->tm_year += (epoch - 1900)) <= 69)
                rtc_tm->tm_year += 100;

        rtc_tm->tm_mon--;
}