// SPDX-License-Identifier: GPL-2.0
/*
 *      Real Time Clock interface for Linux on the BVME6000
 *
 * Based on the PC driver by Paul Gortmaker.
 */

#define RTC_VERSION             "1.00"

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>
#include <linux/capability.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/rtc.h>  /* For struct rtc_time and ioctls, etc */
#include <linux/bcd.h>
#include <asm/bvme6000hw.h>

#include <asm/io.h>
#include <linux/uaccess.h>
#include <asm/setup.h>

/*
 *      We sponge a minor off of the misc major. No need slurping
 *      up another valuable major dev number for this. If you add
 *      an ioctl, make sure you don't conflict with SPARC's RTC
 *      ioctls.
 */

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

static atomic_t rtc_status = ATOMIC_INIT(1);

static long rtc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        volatile RtcPtr_t rtc = (RtcPtr_t)BVME_RTC_BASE;
        unsigned char msr;
        unsigned long flags;
        struct rtc_time wtime;
        void __user *argp = (void __user *)arg;

        switch (cmd) {
        case RTC_RD_TIME:       /* Read the time/date from RTC  */
        {
                local_irq_save(flags);
                /* Ensure clock and real-time-mode-register are accessible */
                msr = rtc->msr & 0xc0;
                rtc->msr = 0x40;
                memset(&wtime, 0, sizeof(struct rtc_time));
                do {
                        wtime.tm_sec =  bcd2bin(rtc->bcd_sec);
                        wtime.tm_min =  bcd2bin(rtc->bcd_min);
                        wtime.tm_hour = bcd2bin(rtc->bcd_hr);
                        wtime.tm_mday =  bcd2bin(rtc->bcd_dom);
                        wtime.tm_mon =  bcd2bin(rtc->bcd_mth)-1;
                        wtime.tm_year = bcd2bin(rtc->bcd_year);
                        if (wtime.tm_year < 70)
                                wtime.tm_year += 100;
                        wtime.tm_wday = bcd2bin(rtc->bcd_dow)-1;
                } while (wtime.tm_sec != bcd2bin(rtc->bcd_sec));
                rtc->msr = msr;
                local_irq_restore(flags);
                return copy_to_user(argp, &wtime, sizeof wtime) ?
                                                                -EFAULT : 0;
        }
        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_ADMIN))
                        return -EACCES;

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

                yrs = rtc_tm.tm_year;
                if (yrs < 1900)
                        yrs += 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;

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

                if ((mon > 12) || (mon < 1) || (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 >= 2070)
                        return -EINVAL;

                local_irq_save(flags);
                /* Ensure clock and real-time-mode-register are accessible */
                msr = rtc->msr & 0xc0;
                rtc->msr = 0x40;

                rtc->t0cr_rtmr = yrs%4;
                rtc->bcd_tenms = 0;
                rtc->bcd_sec   = bin2bcd(sec);
                rtc->bcd_min   = bin2bcd(min);
                rtc->bcd_hr    = bin2bcd(hrs);
                rtc->bcd_dom   = bin2bcd(day);
                rtc->bcd_mth   = bin2bcd(mon);
                rtc->bcd_year  = bin2bcd(yrs%100);
                if (rtc_tm.tm_wday >= 0)
                        rtc->bcd_dow = bin2bcd(rtc_tm.tm_wday+1);
                rtc->t0cr_rtmr = yrs%4 | 0x08;

                rtc->msr = msr;
                local_irq_restore(flags);
                return 0;
        }
        default:
                return -EINVAL;
        }
}

/*
 * We enforce only one user at a time here with the open/close.
 */
static int rtc_open(struct inode *inode, struct file *file)
{
        if (!atomic_dec_and_test(&rtc_status)) {
                atomic_inc(&rtc_status);
                return -EBUSY;
        }
        return 0;
}

static int rtc_release(struct inode *inode, struct file *file)
{
        atomic_inc(&rtc_status);
        return 0;
}

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

static const struct file_operations rtc_fops = {
        .unlocked_ioctl = rtc_ioctl,
        .open           = rtc_open,
        .release        = rtc_release,
        .llseek         = noop_llseek,
};

static struct miscdevice rtc_dev = {
        .minor =        RTC_MINOR,
        .name =         "rtc",
        .fops =         &rtc_fops
};

static int __init rtc_DP8570A_init(void)
{
        if (!MACH_IS_BVME6000)
                return -ENODEV;

        pr_info("DP8570A Real Time Clock Driver v%s\n", RTC_VERSION);
        return misc_register(&rtc_dev);
}
module_init(rtc_DP8570A_init);