rtc-ds1305.c

/*
 * rtc-ds1305.c -- driver for DS1305 and DS1306 SPI RTC chips
 *
 * Copyright (C) 2008 David Brownell
 *
 * 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.
 *
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/bcd.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/workqueue.h>

#include <linux/spi/spi.h>
#include <linux/spi/ds1305.h>
#include <linux/module.h>


/*
 * Registers ... mask DS1305_WRITE into register address to write,
 * otherwise you're reading it.  All non-bitmask values are BCD.
 */
#define DS1305_WRITE		0x80


/* RTC date/time ... the main special cases are that we:
 *  - Need fancy "hours" encoding in 12hour mode
 *  - Don't rely on the "day-of-week" field (or tm_wday)
 *  - Are a 21st-century clock (2000 <= year < 2100)
 */
#define DS1305_RTC_LEN		7		/* bytes for RTC regs */

#define DS1305_SEC		0x00		/* register addresses */
#define DS1305_MIN		0x01
#define DS1305_HOUR		0x02
#	define DS1305_HR_12		0x40	/* set == 12 hr mode */
#	define DS1305_HR_PM		0x20	/* set == PM (12hr mode) */
#define DS1305_WDAY		0x03
#define DS1305_MDAY		0x04
#define DS1305_MON		0x05
#define DS1305_YEAR		0x06


/* The two alarms have only sec/min/hour/wday fields (ALM_LEN).
 * DS1305_ALM_DISABLE disables a match field (some combos are bad).
 *
 * NOTE that since we don't use WDAY, we limit ourselves to alarms
 * only one day into the future (vs potentially up to a week).
 *
 * NOTE ALSO that while we could generate once-a-second IRQs (UIE), we
 * don't currently support them.  We'd either need to do it only when
 * no alarm is pending (not the standard model), or to use the second
 * alarm (implying that this is a DS1305 not DS1306, *and* that either
 * it's wired up a second IRQ we know, or that INTCN is set)
 */
#define DS1305_ALM_LEN		4		/* bytes for ALM regs */
#define DS1305_ALM_DISABLE	0x80

#define DS1305_ALM0(r)		(0x07 + (r))	/* register addresses */
#define DS1305_ALM1(r)		(0x0b + (r))


/* three control registers */
#define DS1305_CONTROL_LEN	3		/* bytes of control regs */

#define DS1305_CONTROL		0x0f		/* register addresses */