path: root/drivers/rtc/rtc-ds1305.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * rtc-ds1305.c -- driver for DS1305 and DS1306 SPI RTC chips
 *
 * Copyright (C) 2008 David Brownell
 */
#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 */
#	define DS1305_nEOSC		0x80	/* low enables oscillator */
#	define DS1305_WP		0x40	/* write protect */
#	define DS1305_INTCN		0x04	/* clear == only int0 used */
#	define DS1306_1HZ		0x04	/* enable 1Hz output */
#	define DS1305_AEI1		0x02	/* enable ALM1 IRQ */
#	define DS1305_AEI0		0x01	/* enable ALM0 IRQ */
#define DS1305_STATUS		0x10
/* status has just AEIx bits, mirrored as IRQFx */
#define DS1305_TRICKLE		0x11
/* trickle bits are defined in <linux/spi/ds1305.h> */

/* a bunch of NVRAM */
#define DS1305_NVRAM_LEN	96		/* bytes of NVRAM */

#define DS1305_NVRAM		0x20		/* register addresses */


struct ds1305 {
	struct spi_device	*spi;
	struct rtc_device	*rtc;

	struct work_struct	work;

	unsigned long		flags;
#define FLAG_EXITING	0

	bool			hr12;
	u8			ctrl[DS1305_CONTROL_LEN];
};


/*----------------------------------------------------------------------*/

/*
 * Utilities ...  tolerate 12-hour AM/PM notation in case of non-Linux
 * software (like a bootloader) which may require it.
 */

static unsigned bcd2hour(u8 bcd)
{
	if (bcd & DS1305_HR_12) {
		unsigned	hour = 0;

		bcd &= ~DS1305_HR_12;
		if (bcd & DS1305_HR_PM) {
			hour = 12;
			bcd &= ~DS1305_HR_PM;
		}
		hour += bcd2bin(bcd);
		return hour - 1;
	}
	return bcd2bin(bcd);
}

static u8 hour2bcd(bool hr12, int hour)
{
	if (hr12) {
		hour++;
		if (hour <= 12)
			return DS1305_HR_12 | bin2bcd(hour);
		hour -= 12;
		return DS1305_HR_12 | DS1305_HR_PM | bin2bcd(hour);
	}
	return bin2bcd(hour);
}

/*----------------------------------------------------------------------*/

/*
 * Interface to RTC framework
 */

static int ds1305_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct ds1305	*ds1305 = dev_get_drvdata(dev);
	u8		buf[2];
	long		err = -EINVAL;

	buf[0] = DS1305_WRITE | DS1305_CONTROL;
	buf[1] = ds1305->ctrl[0];

	if (enabled) {
		if (ds1305->ctrl[0] & DS1305_AEI0)
			goto done;
		buf[1] |= DS1305_AEI0;
	} else {
		if (!(buf[1] & DS1305_AEI0))
			goto done;
		buf[1] &= ~DS1305_AEI0;
	}
	err = spi_write_then_read(ds1305->spi, buf, sizeof(buf), NULL, 0);
	if (err >= 0)
		ds1305->ctrl[0] = buf[1];
done:
	return err;

}


/*
 * Get/set of date and time is pretty normal.
 */

static int ds1305_get_time(struct device *dev, struct rtc_time *time)
{
	struct ds1305	*ds1305 = dev_get_drvdata(dev);
	u8		addr = DS1305_SEC;
	u8		buf[DS1305_RTC_LEN];
	int		status;

	/* Use write-then-read to get all the date/time registers
	 * since dma from stack is nonportable
	 */
	status = spi_write_then_read(ds1305->spi, &addr, sizeof(addr),
			buf, sizeof(buf));
	if (status < 0)
		return status;

	dev_vdbg(dev, "%s: %3ph, %4ph\n", "read", &buf[0], &buf[3]);

	/* Decode the registers */
	time->tm_sec = bcd2bin(buf[DS1305_SEC]);
	time->tm_min = bcd2bin(buf[DS1305_MIN]);
	time->tm_hour = bcd2hour(buf[DS1305_HOUR]);
	time->tm_wday = buf[DS1305_WDAY] - 1;
	time->tm_mday = bcd2bin(buf[DS1305_MDAY]);
	time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1;
	time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100;

	dev_vdbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
		"read", time->tm_sec, time->tm_min,
		time->tm_hour, time->tm_mday,
		time->tm_mon, time->tm_year, time->tm_wday);

	return 0;
}

static int ds1305_set_time(struct device *dev, struct rtc_time *time)
{
	struct ds1305	*ds1305 = dev_get_drvdata(dev);
	u8		buf[1 + DS1305_RTC_LEN];
	u8		*bp = buf;

	dev_vdbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
		"write", time->tm_sec, time->tm_min,
		time->tm_hour, time->tm_mday,
		time->tm_mon, time->tm_year, time->tm_wday);

	/* Write registers starting at the first time/date address. */
	*bp++ = DS1305_WRITE | DS1305_SEC;

	*bp++ = bin2bcd(time->tm_sec);
	*bp++ = bin2bcd(time->tm_min);
	*bp++ = hour2bcd(ds1305->hr12, time->tm_hour);
	*bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1;
	*bp++ = bin2bcd(time->tm_mday);
	*bp++ = bin2bcd(time->tm_mon + 1);
	*bp++ = bin2bcd(time->tm_year