/*
 *  Driver for NEC VR4100 series Real Time Clock unit.
 *
 *  Copyright (C) 2003-2008  Yoichi Yuasa <yuasa@linux-mips.org>
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/log2.h>

#include <asm/div64.h>
#include <asm/io.h>
#include <asm/uaccess.h>

MODULE_AUTHOR("Yoichi Yuasa <yuasa@linux-mips.org>");
MODULE_DESCRIPTION("NEC VR4100 series RTC driver");
MODULE_LICENSE("GPL v2");

/* RTC 1 registers */
#define ETIMELREG		0x00
#define ETIMEMREG		0x02
#define ETIMEHREG		0x04
/* RFU */
#define ECMPLREG		0x08
#define ECMPMREG		0x0a
#define ECMPHREG		0x0c
/* RFU */
#define RTCL1LREG		0x10
#define RTCL1HREG		0x12
#define RTCL1CNTLREG		0x14
#define RTCL1CNTHREG		0x16
#define RTCL2LREG		0x18
#define RTCL2HREG		0x1a
#define RTCL2CNTLREG		0x1c
#define RTCL2CNTHREG		0x1e

/* RTC 2 registers */
#define TCLKLREG		0x00
#define TCLKHREG		0x02
#define TCLKCNTLREG		0x04
#define TCLKCNTHREG		0x06
/* RFU */
#define RTCINTREG		0x1e
 #define TCLOCK_INT		0x08
 #define RTCLONG2_INT		0x04
 #define RTCLONG1_INT		0x02
 #define ELAPSEDTIME_INT	0x01

#define RTC_FREQUENCY		32768
#define MAX_PERIODIC_RATE	6553

static void __iomem *rtc1_base;
static void __iomem *rtc2_base;

#define rtc1_read(offset)		readw(rtc1_base + (offset))
#define rtc1_write(offset, value)	writew((value), rtc1_base + (offset))

#define rtc2_read(offset)		readw(rtc2_base + (offset))
#define rtc2_write(offset, value)	writew((value), rtc2_base + (offset))

static unsigned long epoch = 1970;	/* Jan 1 1970 00:00:00 */

static DEFINE_SPINLOCK(rtc_lock);
static char rtc_name[] = "RTC";
static unsigned long periodic_count;
static unsigned int alarm_enabled;
static int aie_irq;
static int pie_irq;

static inline unsigned long read_elapsed_second(void)
{

	unsigned long first_low, first_mid, first_high;

	unsigned long second_low, second_mid, second_high;

	do {
		first_low = rtc1_read(ETIMELREG);
		first_mid = rtc1_read(ETIMEMREG);
		first_high = rtc1_read(ETIMEHREG);
		second_low = rtc1_read(ETIMELREG);
		second_mid = rtc1_read(ETIMEMREG);
		second_high = rtc1_read(ETIMEHREG);
	} while (first_low != second_low || first_mid != second_mid ||
	         first_high != second_high);

	return (first_high << 17) | (first_mid << 1) | (first_low >> 15);
}

static inline void write_elapsed_second(unsigned long sec)
{
	spin_lock_irq(&rtc_lock);

	rtc1_write(ETIMELREG, (uint16_t)(sec << 15));
	rtc1_write(ETIMEMREG, (uint16_t)(sec >> 1));
	rtc1_write(ETIMEHREG, (uint16_t)(sec >> 17));

	spin_unlock_irq(&rtc_lock);
}

static void vr41xx_rtc_release(struct device *dev)
{

	spin_lock_irq(&rtc_lock);

	rtc1_write(ECMPLREG, 0);
	rtc1_write(ECMPMREG, 0);
	rtc1_write(ECMPHREG, 0);
	rtc1_write(RTCL1LREG, 0);
	rtc1_write(RTCL1HREG, 0);

	spin_unlock_irq(&rtc_lock);

	disable_irq(aie_irq);
	disable_irq(pie_irq);
}

static int vr41xx_rtc_read_time(struct device *dev, struct rtc_time *time)
{
	unsigned long epoch_sec, elapsed_sec;

	epoch_sec = mktime(epoch, 1, 1, 0, 0, 0);
	elapsed_sec = read_elapsed_second();

	rtc_time_to_tm(epoch_sec + elapsed_sec, time);

	return 0;
}

static int vr41xx_rtc_set_time(struct device *dev, struct rtc_time *time)
{
	unsigned long epoch_sec, current_sec;

	epoch_sec = mktime(epoch, 1, 1, 0, 0, 0);
	current_sec = mktime(time->tm_year + 1900, time->tm_mon + 1, time->tm_mday,
	                     time->tm_hour, time->tm_min, time->tm_sec);

	write_elapsed_second(current_sec - epoch_sec);

	return 0;
}

static int vr41xx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
	unsigned long low, mid, high;
	struct rtc_time *time = &wkalrm->time;

	spin_lock_irq(&rtc_lock);

	low = rtc1_read(ECMPLREG);
	mid = rtc1_read(ECMPMREG);
	high = rtc1_read(ECMPHREG);
	wkalrm->enabled = alarm_enabled;

	spin_unlock_irq(&rtc_lock);

	rtc_time_to_tm((high << 17) | (mid << 1) | (low >> 15), time);

	return 0;
}

static int vr41xx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
{
	unsigned long alarm_sec;
	struct rtc_time *time = &wkalrm->time;

	alarm_sec = mktime(time->tm_year + 1900, time->tm_mon + 1, time->tm_mday,
	                   time->tm_hour, time->tm_min, time->tm_sec);

	spin_lock_irq(&rtc_lock);

	if (alarm_enabled)
		disable_irq(aie_irq);

	rtc1_write(ECMPLREG, (uint16_t)(alarm_sec << 15));
	rtc1_write(ECMPMREG, (uint16_t)(alarm_sec >> 1));
	rtc1_write(ECMPHREG, (uint16_t)(alarm_sec >> 17));

	if (wkalrm->enabled)
		enable_irq(aie_irq);

	alarm_enabled = wkalrm->enabled;

	spin_unlock_irq(&rtc_lock);

	return 0;
}

static int vr41xx_rtc_irq_set_freq(struct device *dev, int freq)
{
	u64 count;

	if (!is_power_of_2(freq))
		return -EINVAL;
	count = RTC_FREQUENCY;
	do_div(count, freq);

	spin_lock_irq(&rtc_lock);

	periodic_count = count;
	rtc1_write(RTCL1LREG, periodic_count);
	rtc1_write(RTCL1HREG, periodic_count >> 16);

	spin_unlock_irq(&rtc_lock);

	return 0;
}

static int vr41xx_rtc_irq_set_state(struct device *dev, int enabled)
{
	if (enabled)
		enable_irq(pie_irq);
	else
		disable_irq(pie_irq);

	return 0;
}

static int vr41xx_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case RTC_AIE_ON:
		spin_lock_irq(&rtc_lock);

		if (!alarm_enabled) {
			enable_irq(aie_irq);
			alarm_enabled = 1;
		}

		spin_unlock_irq(&rtc_lock);
		break;
	case RTC_AIE_OFF:
		spin_lock_irq(&rtc_lock);

		if (alarm_enabled) {
			disable_irq(aie_irq);
			alarm_enabled = 0;
		}