ds1302.c

/*!***************************************************************************
*!
*! FILE NAME  : ds1302.c
*!
*! DESCRIPTION: Implements an interface for the DS1302 RTC through Etrax I/O
*!
*! Functions exported: ds1302_readreg, ds1302_writereg, ds1302_init
*!
*! ---------------------------------------------------------------------------
*!
*! (C) Copyright 1999-2007 Axis Communications AB, LUND, SWEDEN
*!
*!***************************************************************************/


#include <linux/fs.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/bcd.h>
#include <linux/capability.h>

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

#include "i2c.h"

#define RTC_MAJOR_NR 121 /* local major, change later */

static const char ds1302_name[] = "ds1302";

/* The DS1302 might be connected to different bits on different products. 
 * It has three signals - SDA, SCL and RST. RST and SCL are always outputs,
 * but SDA can have a selected direction.
 * For now, only PORT_PB is hardcoded.
 */

/* The RST bit may be on either the Generic Port or Port PB. */
#ifdef CONFIG_ETRAX_DS1302_RST_ON_GENERIC_PORT
#define TK_RST_OUT(x) REG_SHADOW_SET(R_PORT_G_DATA,  port_g_data_shadow,  CONFIG_ETRAX_DS1302_RSTBIT, x)
#define TK_RST_DIR(x)
#else
#define TK_RST_OUT(x) REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, CONFIG_ETRAX_DS1302_RSTBIT, x)
#define TK_RST_DIR(x) REG_SHADOW_SET(R_PORT_PB_DIR,  port_pb_dir_shadow,  CONFIG_ETRAX_DS1302_RSTBIT, x)
#endif


#define TK_SDA_OUT(x) REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, CONFIG_ETRAX_DS1302_SDABIT, x)
#define TK_SCL_OUT(x) REG_SHADOW_SET(R_PORT_PB_DATA, port_pb_data_shadow, CONFIG_ETRAX_DS1302_SCLBIT, x)

#define TK_SDA_IN()   ((*R_PORT_PB_READ >> CONFIG_ETRAX_DS1302_SDABIT) & 1)
/* 1 is out, 0 is in */
#define TK_SDA_DIR(x) REG_SHADOW_SET(R_PORT_PB_DIR,  port_pb_dir_shadow,  CONFIG_ETRAX_DS1302_SDABIT, x)
#define TK_SCL_DIR(x) REG_SHADOW_SET(R_PORT_PB_DIR,  port_pb_dir_shadow,  CONFIG_ETRAX_DS1302_SCLBIT, x)


/*
 * The reason for tempudelay and not udelay is that loops_per_usec
 * (used in udelay) is not set when functions here are called from time.c 
 */

static void tempudelay(int usecs) 
{
	volatile int loops;

	for(loops = usecs * 12; loops > 0; loops--)
		/* nothing */;	
}


/* Send 8 bits. */
static void
out_byte(unsigned char x) 
{
	int i;
	TK_SDA_DIR(1);
	for (i = 8; i--;) {
		/* The chip latches incoming bits on the rising edge of SCL. */
		TK_SCL_OUT(0);
		TK_SDA_OUT(x & 1);
		tempudelay(1);
		TK_SCL_OUT(1);
		tempudelay(1);
		x >>= 1;
	}
	TK_SDA_DIR(0);
}

static unsigned char
in_byte(void) 
{
	unsigned char x = 0;
	int i;

	/* Read byte. Bits come LSB first, on the falling edge of SCL.
	 * Assume SDA is in input direction already.
	 */
	TK_SDA_DIR(0);

	for (i = 8; i--;) {
		TK_SCL_OUT(0);
		tempudelay(1);
		x >>= 1;
		x |= (TK_SDA_IN() << 7);
		TK_SCL_OUT(1);
		tempudelay(1);
	}

	return x;
}

/* Prepares for a transaction by de-activating RST (active-low). */

static void
start(void) 
{
	TK_SCL_OUT(0);
	tempudelay(1);
	TK_RST_OUT(0);
	tempudelay(5);
	TK_RST_OUT(1);	
}

/* Ends a transaction by taking RST active again. */

static void
stop(void) 
{
	tempudelay(2);
	TK_RST_OUT(0);
}

/* Enable writing. */

static void
ds1302_wenable(void) 
{
	start(); 	
	out_byte(0x8e); /* Write control register  */
	out_byte(0x00); /* Disable write protect bit 7 = 0 */
	stop();
}

/* Disable writing. */

static void
ds1302_wdisable(void) 
{
	start();
	out_byte(0x8e); /* Write control register  */
	out_byte(0x80); /* Disable write protect bit 7 = 0 */
	stop();
}



/* Read a byte from the selected register in the DS1302. */

unsigned char
ds1302_readreg(int reg) 
{
	unsigned char x;

	start();
	out_byte(0x81 | (reg << 1)); /* read register */
	x = in_byte();
	stop();

	return x;
}

/* Write a byte to the selected register. */

void
ds1302_writereg(int reg, unsigned char val) 
{
#ifndef CONFIG_ETRAX_RTC_READONLY
	int do_writereg = 1;
#else
	int do_writereg = 0;

	if (reg == RTC_TRICKLECHARGER)
		do_writereg = 1;
#endif

	if (do_writereg) {
		ds1302_wenable();
		start();
		out_byte(0x80 | (reg << 1)); /* write register */
		out_byte(val);
		stop();
		ds1302_wdisable();
	}
}

void
get_rtc_time(struct rtc_time *rtc_tm) 
{
	unsigned long flags;

	local_irq_save(flags);

	rtc_tm->tm_sec = CMOS_READ(RTC_SECONDS);
	rtc_tm->tm_min = CMOS_READ(RTC_MINUTES);
	rtc_tm->tm_hour = CMOS_READ(RTC_HOURS);
	rtc_tm->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
	rtc_tm->tm_mon = CMOS_READ(RTC_MONTH);
	rtc_tm->tm_year = CMOS_READ(RTC_YEAR);

	local_irq_restore(flags);
	
	BCD_TO_BIN(rtc_tm->tm_sec);
	BCD_TO_BIN(rtc_tm->tm_min);
	BCD_TO_BIN(rtc_tm->tm_hour);
	BCD_TO_BIN(rtc_tm->tm_mday);
	BCD_TO_BIN(rtc_tm->tm_mon);
	BCD_TO_BIN(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 <= 69)
		rtc_tm->tm_year += 100;

	rtc_tm->tm_mon--;
}

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

/* ioctl that supports RTC_RD_TIME and RTC_SET_TIME (read and set time/date). */

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

	switch(cmd) {
		case RTC_RD_TIME:	/* read the time/date from RTC	*/
		{
			struct rtc_time rtc_tm;
						
			memset(&rtc_tm, 0, sizeof (struct rtc_time));
			get_rtc_time(&rtc_tm);						
			if (copy_to_user((struct rtc_time*)arg, &rtc_tm, sizeof(struct rtc_time)))
				return -EFAULT;	
			return 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_TIME))
				return -EPERM;

			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) || (yrs > 2069))
				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 >= 2000)
				yrs -= 2000;	/* RTC (0, 1, ... 69) */
			else
				yrs -= 1900;	/* RTC (70, 71, ... 99) */

			BIN_TO_BCD(sec);
			BIN_TO_BCD(min);
			BIN_TO_BCD(hrs);
			BIN_TO_BCD(day);
			BIN_TO_BCD(mon);
			BIN_TO_BCD(yrs);

			local_irq_save(flags);
			CMOS_WRITE(yrs, RTC_YEAR);
			CMOS_WRITE(mon, RTC_MONTH);
			CMOS_WRITE(day, RTC_DAY_OF_MONTH);
			CMOS_WRITE(hrs, RTC_HOURS);
			CMOS_WRITE(min, RTC_MINUTES);
			CMOS_WRITE(sec, RTC_SECONDS);
			local_irq_restore(flags);

			/* Notice that at this point, the RTC is updated but
			 * the kernel is still running with the old time.
			 * You need to set that separately with settimeofday
			 * or adjtimex.
			 */
			return 0;
		}

		case RTC_SET_CHARGE: /* set the RTC TRICKLE CHARGE register */
		{
			int tcs_val;

			if (!capable(CAP_SYS_TIME))
				return -EPERM;
			
			if(copy_from_user(&tcs_val, (int*)arg, sizeof(int)))
				return -EFAULT;

			tcs_val = RTC_TCR_PATTERN | (tcs_val & 0x0F);
			ds1302_writereg(RTC_TRICKLECHARGER, tcs_val);
			return 0;
		}
		case RTC_VLOW_RD:
		{
			/* TODO:
			 * Implement voltage low detection support
			 */
			printk(KERN_WARNING "DS1302: RTC Voltage Low detection"
			       " is not supported\n");
			return 0;
		}
		case RTC_VLOW_SET:
		{
			/* TODO:
			 * Nothing to do since Voltage Low detection is not supported
			 */
			return 0;
		}
		default:
			return -ENOIOCTLCMD;
	}
}

static void
print_rtc_status(void)
{
	struct rtc_time tm;

	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.
	 */

	printk(KERN_INFO "rtc_time\t: %02d:%02d:%02d\n",
	       tm.tm_hour, tm.tm_min, tm.tm_sec);
	printk(KERN_INFO "rtc_date\t: %04d-%02d-%02d\n",
	       tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
}

/* The various file operations we support. */

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

/* Probe for the chip by writing something to its RAM and try reading it back. */

#define MAGIC_PATTERN 0x42

static int __init
ds1302_probe(void) 
{
	int retval, res; 

	TK_RST_DIR(1);
	TK_SCL_DIR(1);
	TK_SDA_DIR(0);
	
	/* Try to talk to timekeeper. */

	ds1302_wenable();  
	start();
	out_byte(0xc0); /* write RAM byte 0 */	
	out_byte(MAGIC_PATTERN); /* write something magic */
	start();
	out_byte(0xc1); /* read RAM byte 0 */

	if((res = in_byte()) == MAGIC_PATTERN) {
		stop();
		ds1302_wdisable();
		printk(KERN_INFO "%s: RTC found.\n", ds1302_name);
		printk(KERN_INFO "%s: SDA, SCL, RST on PB%i, PB%i, %s%i\n",
		       ds1302_name,
		       CONFIG_ETRAX_DS1302_SDABIT,
		       CONFIG_ETRAX_DS1302_SCLBIT,
#ifdef CONFIG_ETRAX_DS1302_RST_ON_GENERIC_PORT
		       "GENIO",
#else
		       "PB",
#endif
		       CONFIG_ETRAX_DS1302_RSTBIT);
		       print_rtc_status();
		retval = 1;
	} else {
		stop();
		retval = 0;
	}

	return retval;
}


/* Just probe for the RTC and register the device to handle the ioctl needed. */

int __init
ds1302_init(void) 
{
#ifdef CONFIG_ETRAX_I2C
	i2c_init();
#endif

	if (!ds1302_probe()) {
#ifdef CONFIG_ETRAX_DS1302_RST_ON_GENERIC_PORT
#if CONFIG_ETRAX_DS1302_RSTBIT == 27
		/*
		 * The only way to set g27 to output is to enable ATA.
		 *
		 * Make sure that R_GEN_CONFIG is setup correct.
		 */
		/* Allocating the ATA interface will grab almost all
		 * pins in I/O groups a, b, c and d.  A consequence of
		 * allocating the ATA interface is that the fixed
		 * interfaces shared RAM, parallel port 0, parallel
		 * port 1, parallel port W, SCSI-8 port 0, SCSI-8 port
		 * 1, SCSI-W, serial port 2, serial port 3,
		 * synchronous serial port 3 and USB port 2 and almost
		 * all GPIO pins on port g cannot be used.
		 */
		if (cris_request_io_interface(if_ata, "ds1302/ATA")) {
			printk(KERN_WARNING "ds1302: Failed to get IO interface\n");
			return -1;
		}

#elif CONFIG_ETRAX_DS1302_RSTBIT == 0
		if (cris_io_interface_allocate_pins(if_gpio_grp_a,
						    'g',
						    CONFIG_ETRAX_DS1302_RSTBIT,
						    CONFIG_ETRAX_DS1302_RSTBIT)) {
			printk(KERN_WARNING "ds1302: Failed to get IO interface\n");
			return -1;
		}

		/* Set the direction of this bit to out. */
		genconfig_shadow = ((genconfig_shadow &
 				     ~IO_MASK(R_GEN_CONFIG, g0dir)) |
 				   (IO_STATE(R_GEN_CONFIG, g0dir, out)));
		*R_GEN_CONFIG = genconfig_shadow;
#endif
		if (!ds1302_probe()) {
			printk(KERN_WARNING "%s: RTC not found.\n", ds1302_name);
			return -1;
		}
#else
		printk(KERN_WARNING "%s: RTC not found.\n", ds1302_name);
		return -1;
#endif
  	}
	/* Initialise trickle charger */
	ds1302_writereg(RTC_TRICKLECHARGER,
			RTC_TCR_PATTERN |(CONFIG_ETRAX_DS1302_TRICKLE_CHARGE & 0x0F));
        /* Start clock by resetting CLOCK_HALT */
	ds1302_writereg(RTC_SECONDS, (ds1302_readreg(RTC_SECONDS) & 0x7F));
	return 0;
}

static int __init ds1302_register(void)
{
	ds1302_init();
	if (register_chrdev(RTC_MAJOR_NR, ds1302_name, &rtc_fops)) {
		printk(KERN_INFO "%s: unable to get major %d for rtc\n", 
		       ds1302_name, RTC_MAJOR_NR);
		return -1;
	}
        return 0;

}

module_init(ds1302_register);