/*
 *  linux/drivers/acorn/char/i2c.c
 *
 *  Copyright (C) 2000 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  ARM IOC/IOMD i2c driver.
 *
 *  On Acorn machines, the following i2c devices are on the bus:
 *	- PCF8583 real time clock & static RAM
 */
#include <linux/capability.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/miscdevice.h>
#include <linux/rtc.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/fs.h>

#include <asm/hardware.h>
#include <asm/io.h>
#include <asm/hardware/ioc.h>
#include <asm/system.h>
#include <asm/uaccess.h>

#include "pcf8583.h"

extern int (*set_rtc)(void);

static struct i2c_client *rtc_client;
static const unsigned char days_in_mon[] = 
	{ 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

#define CMOS_CHECKSUM	(63)

/*
 * Acorn machines store the year in the static RAM at
 * location 128.
 */
#define CMOS_YEAR	(64 + 128)

static inline int rtc_command(int cmd, void *data)
{
	int ret = -EIO;

	if (rtc_client)
		ret = rtc_client->driver->command(rtc_client, cmd, data);

	return ret;
}

/*
 * Update the century + year bytes in the CMOS RAM, ensuring
 * that the check byte is correctly adjusted for the change.
 */
static int rtc_update_year(unsigned int new_year)
{
	unsigned char yr[2], chk;
	struct mem cmos_year  = { CMOS_YEAR, sizeof(yr), yr };
	struct mem cmos_check = { CMOS_CHECKSUM, 1, &chk };
	int ret;

	ret = rtc_command(MEM_READ, &cmos_check);
	if (ret)
		goto out;
	ret = rtc_command(MEM_READ, &cmos_year);
	if (ret)
		goto out;

	chk -= yr[1] + yr[0];

	yr[1] = new_year / 100;
	yr[0] = new_year % 100;

	chk += yr[1] + yr[0];

	ret = rtc_command(MEM_WRITE, &cmos_year);
	if (ret == 0)
		ret = rtc_command(MEM_WRITE, &cmos_check);
 out:
	return ret;
}

/*
 * Read the current RTC time and date, and update xtime.
 */
static void get_rtc_time(struct rtc_tm *rtctm, unsigned int *year)
{
	unsigned char ctrl, yr[2];
	struct mem rtcmem = { CMOS_YEAR, sizeof(yr), yr };
	int real_year, year_offset;

	/*
	 * Ensure that the RTC is running.
	 */
	rtc_command(RTC_GETCTRL, &ctrl);
	if (ctrl & 0xc0) {
		unsigned char new_ctrl = ctrl & ~0xc0;

		printk(KERN_WARNING "RTC: resetting control %02x -> %02x\n",
		       ctrl, new_ctrl);

		rtc_command(RTC_SETCTRL, &new_ctrl);
	}

	if (rtc_command(RTC_GETDATETIME, rtctm) ||
	    rtc_command(MEM_READ, &rtcmem))
		return;

	real_year = yr[0];

	/*
	 * The RTC year holds the LSB two bits of the current
	 * year, which should reflect the LSB two bits of the
	 * CMOS copy of the year.  Any difference indicates
	 * that we have to correct the CMOS version.
	 */
	year_offset = rtctm->year_off - (real_year & 3);
	if (year_offset < 0)
		/*
		 * RTC year wrapped.  Adjust it appropriately.
		 */
		year_offset += 4;

	*year = real_year + year_offset + yr[1] * 100;
}

static int set_rtc_time(struct rtc_tm *rtctm, unsigned int year)
{
	unsigned char leap;
	int ret;

	leap = (!(year % 4) && (year % 100)) || !(year % 400);

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

	if (rtctm->mday > (days_in_mon[rtctm->mon] + (rtctm->mon == 2 && leap)))
		return -EINVAL;

	if (rtctm->hours >= 24 || rtctm->mins >= 60 || rtctm->secs >= 60)
		return -EINVAL;

	/*
	 * The RTC's own 2-bit year must reflect the least
	 * significant two bits of the CMOS year.
	 */
	rtctm->year_off = (year % 100) & 3;

	ret = rtc_command(RTC_SETDATETIME, rtctm);
	if (ret == 0)
		ret = rtc_update_year(year);

	return ret;
}

/*
 * Set the RTC time only.  Note that
 * we do not touch the date.
 */
static int k_set_rtc_time(void)
{
	struct rtc_tm new_rtctm, old_rtctm;
	unsigned long nowtime = xtime.tv_sec;

	if (rtc_command(RTC_GETDATETIME, &old_rtctm))
		return 0;

	new_rtctm.cs    = xtime.tv_nsec / 10000000;
	new_rtctm.secs  = nowtime % 60;	nowtime /= 60;
	new_rtctm.mins  = nowtime % 60;	nowtime /= 60;
	new_rtctm.hours = nowtime % 24;

	/*
	 * avoid writing when we're going to change the day
	 * of the month.  We will retry in the next minute.
	 * This basically means that if the RTC must not drift
	 * by more than 1 minute in 11 minutes.
	 *
	 * [ rtc: 1/1/2000 23:58:00, real 2/1/2000 00:01:00,
	 *   rtc gets set to 1/1/2000 00:01:00 ]
	 */
	if ((old_rtctm.hours == 23 && old_rtctm.mins == 59) ||
	    (new_rtctm.hours == 23 && new_rtctm.mins == 59))
		return 1;

	return rtc_command(RTC_SETTIME, &new_rtctm);
}

static int rtc_ioctl(struct inode *inode, struct file *file,
		     unsigned int cmd, unsigned long arg)
{
	unsigned int year;
	struct rtc_time rtctm;
	struct rtc_tm rtc_raw;

	switch (cmd) {
	case RTC_ALM_READ:
	case RTC_ALM_SET:
		break;

	case RTC_RD_TIME:
		memset(&rtctm, 0, sizeof(struct rtc_time));
		get_rtc_time(&rtc_raw, &year);
		rtctm.tm_sec  = rtc_raw.secs;
		rtctm.tm_min  = rtc_raw.mins;
		rtctm.tm_hour = rtc_raw.hours;
		rtctm.tm_mday = rtc_raw.mday;
		rtctm.tm_mon  = rtc_raw.mon - 1; /* month starts at 0 */
		rtctm.tm_year = year - 1900; /* starts at 1900 */
		return copy_to_user((void *)arg, &rtctm, sizeof(rtctm))
				 ? -EFAULT : 0;

	case RTC_SET_TIME:
		if (!capable(CAP_SYS_TIME))
			return -EACCES;

		if (copy_from_user(&rtctm, (void *)arg, sizeof(rtctm)))
			return -EFAULT;
		rtc_raw.secs     = rtctm.tm_sec;
		rtc_raw.mins     = rtctm.tm_min;
		rtc_raw.hours    = rtctm.tm_hour;
		rtc_raw.mday     = rtctm.tm_mday;
		rtc_raw.mon      = rtctm.tm_mon + 1;
		year             = rtctm.tm_year + 1900;
		return set_rtc_time(&rtc_raw, year);
		break;

	case RTC_EPOCH_READ:
		return put_user(1900, (unsigned long *)arg);

	}
	return -EINVAL;
}

static struct file_operations rtc_fops = {
	.ioctl	= rtc_ioctl,
};

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

/* IOC / IOMD i2c driver */

#define FORCE_ONES	0xdc
#define SCL		0x02
#define SDA		0x01

/*
 * We must preserve all non-i2c output bits in IOC_CONTROL.
 * Note also that we need to preserve the value of SCL and
 * SDA outputs as well (which may be different from the
 * values read back from IOC_CONTROL).
 */
static u_int force_ones;

static void ioc_setscl(void *data, int state)
{
	u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
	u_int ones = force_ones;

	if (state)
		ones |= SCL;
	else
		ones &= ~SCL;

	force_ones = ones;

 	ioc_writeb(ioc_control | ones, IOC_CONTROL);
}

static void ioc_setsda(void *data, int state)
{
	u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
	u_int ones = force_ones;

	if (state)
		ones |= SDA;
	else
		ones &= ~SDA;

	force_ones = ones;

 	ioc_writeb(ioc_control | ones, IOC_CONTROL);
}

static int ioc_getscl(void *data)
{
	return (ioc_readb(IOC_CONTROL) & SCL) != 0;
}

static int ioc_getsda(void *data)
{
	return (ioc_readb(IOC_CONTROL) & SDA) != 0;
}

static struct i2c_algo_bit_data ioc_data = {
	.setsda		= ioc_setsda,
	.setscl		= ioc_setscl,
	.getsda		= ioc_getsda,
	.getscl		= ioc_getscl,
	.udelay		= 80,
	.timeout	= 100
};

static int ioc_client_reg(struct i2c_client *client)
{
	if (client->driver->id == I2C_DRIVERID_PCF8583 &&
	    client->addr == 0x50) {
		struct rtc_tm rtctm;
		unsigned int year;
		struct timespec tv;

		rtc_client = client;
		get_rtc_time(&rtctm, &year);

		tv.tv_nsec = rtctm.cs * 10000000;
		tv.tv_sec  = mktime(year, rtctm.mon, rtctm.mday,
				    rtctm.hours, rtctm.mins, rtctm.secs);
		do_settimeofday(&tv);
		set_rtc = k_set_rtc_time;
	}

	return 0;
}

static int ioc_client_unreg(struct i2c_client *client)
{
	if (client == rtc_client) {
		set_rtc = NULL;
		rtc_client = NULL;
	}

	return 0;
}

static struct i2c_adapter ioc_ops = {
	.id			= I2C_HW_B_IOC,
	.algo_data		= &ioc_data,
	.client_register	= ioc_client_reg,
	.client_unregister	= ioc_client_unreg,
};

static int __init i2c_ioc_init(void)
{
	int ret;

	force_ones = FORCE_ONES | SCL | SDA;

	ret = i2c_bit_add_bus(&ioc_ops);

	if (ret >= 0){
		ret = misc_register(&rtc_dev);
		if(ret < 0)
			i2c_del_adapter(&ioc_ops);
	}

	return ret;
}

__initcall(i2c_ioc_init);