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Commit 8fc2c767 authored by Kim B. Heino's avatar Kim B. Heino Committed by Linus Torvalds
Browse files

rtc: add support for ST M41T94 SPI RTC 



This patch adds kernel driver for M41T94 RTC chip connected via SPI.
I've tested it on two different AT91-based hardwares.

This is third revision of the patch: some comments made by
Alessandro Zummo fixed.

Revision two added support for century bit and fixes.

Signed-off-by: default avatarKim B. Heino <Kim.Heino@bluegiga.com>
Signed-off-by: default avatarAlessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5ad31a57

drivers/rtc/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -273,6 +273,15 @@ comment "SPI RTC drivers" 


if SPI_MASTER



config RTC_DRV_M41T94

	tristate "ST M41T94"

	help

	  If you say yes here you will get support for the

	  ST M41T94 SPI RTC chip.



	  This driver can also be built as a module. If so, the module

	  will be called rtc-m41t94.



config RTC_DRV_MAX6902

	tristate "Maxim MAX6902"

	help

drivers/rtc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ obj-$(CONFIG_RTC_DRV_EP93XX) += rtc-ep93xx.o 
obj-$(CONFIG_RTC_DRV_FM3130)	+= rtc-fm3130.o

obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o

obj-$(CONFIG_RTC_DRV_M41T80)	+= rtc-m41t80.o

obj-$(CONFIG_RTC_DRV_M41T94)	+= rtc-m41t94.o

obj-$(CONFIG_RTC_DRV_M48T59)	+= rtc-m48t59.o

obj-$(CONFIG_RTC_DRV_M48T86)	+= rtc-m48t86.o

obj-$(CONFIG_RTC_DRV_MAX6900)	+= rtc-max6900.o

drivers/rtc/rtc-m41t94.c

0 → 100644
+173 −0
Original line number Diff line number Diff line 
/*

 * Driver for ST M41T94 SPI RTC

 *

 * Copyright (C) 2008 Kim B. Heino

 *

 * 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/module.h>

#include <linux/kernel.h>

#include <linux/platform_device.h>

#include <linux/rtc.h>

#include <linux/spi/spi.h>

#include <linux/bcd.h>



#define M41T94_REG_SECONDS	0x01

#define M41T94_REG_MINUTES	0x02

#define M41T94_REG_HOURS	0x03

#define M41T94_REG_WDAY		0x04

#define M41T94_REG_DAY		0x05

#define M41T94_REG_MONTH	0x06

#define M41T94_REG_YEAR		0x07

#define M41T94_REG_HT		0x0c



#define M41T94_BIT_HALT		0x40

#define M41T94_BIT_STOP		0x80

#define M41T94_BIT_CB		0x40

#define M41T94_BIT_CEB		0x80



static int m41t94_set_time(struct device *dev, struct rtc_time *tm)

{

	struct spi_device *spi = to_spi_device(dev);

	u8 buf[8]; /* write cmd + 7 registers */



	dev_dbg(dev, "%s secs=%d, mins=%d, "

		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",

		"write", tm->tm_sec, tm->tm_min,

		tm->tm_hour, tm->tm_mday,

		tm->tm_mon, tm->tm_year, tm->tm_wday);



	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */

	buf[M41T94_REG_SECONDS] = BIN2BCD(tm->tm_sec);

	buf[M41T94_REG_MINUTES] = BIN2BCD(tm->tm_min);

	buf[M41T94_REG_HOURS]   = BIN2BCD(tm->tm_hour);

	buf[M41T94_REG_WDAY]    = BIN2BCD(tm->tm_wday + 1);

	buf[M41T94_REG_DAY]     = BIN2BCD(tm->tm_mday);

	buf[M41T94_REG_MONTH]   = BIN2BCD(tm->tm_mon + 1);



	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;

	if (tm->tm_year >= 100)

		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;

	buf[M41T94_REG_YEAR] = BIN2BCD(tm->tm_year % 100);



	return spi_write(spi, buf, 8);

}



static int m41t94_read_time(struct device *dev, struct rtc_time *tm)

{

	struct spi_device *spi = to_spi_device(dev);

	u8 buf[2];

	int ret, hour;



	/* clear halt update bit */

	ret = spi_w8r8(spi, M41T94_REG_HT);

	if (ret < 0)

		return ret;

	if (ret & M41T94_BIT_HALT) {

		buf[0] = 0x80 | M41T94_REG_HT;

		buf[1] = ret & ~M41T94_BIT_HALT;

		spi_write(spi, buf, 2);

	}



	/* clear stop bit */

	ret = spi_w8r8(spi, M41T94_REG_SECONDS);

	if (ret < 0)

		return ret;

	if (ret & M41T94_BIT_STOP) {

		buf[0] = 0x80 | M41T94_REG_SECONDS;

		buf[1] = ret & ~M41T94_BIT_STOP;

		spi_write(spi, buf, 2);

	}



	tm->tm_sec  = BCD2BIN(spi_w8r8(spi, M41T94_REG_SECONDS));

	tm->tm_min  = BCD2BIN(spi_w8r8(spi, M41T94_REG_MINUTES));

	hour = spi_w8r8(spi, M41T94_REG_HOURS);

	tm->tm_hour = BCD2BIN(hour & 0x3f);

	tm->tm_wday = BCD2BIN(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;

	tm->tm_mday = BCD2BIN(spi_w8r8(spi, M41T94_REG_DAY));

	tm->tm_mon  = BCD2BIN(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;

	tm->tm_year = BCD2BIN(spi_w8r8(spi, M41T94_REG_YEAR));

	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))

		tm->tm_year += 100;



	dev_dbg(dev, "%s secs=%d, mins=%d, "

		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",

		"read", tm->tm_sec, tm->tm_min,

		tm->tm_hour, tm->tm_mday,

		tm->tm_mon, tm->tm_year, tm->tm_wday);



	/* initial clock setting can be undefined */

	return rtc_valid_tm(tm);

}



static const struct rtc_class_ops m41t94_rtc_ops = {

	.read_time	= m41t94_read_time,

	.set_time	= m41t94_set_time,

};



static struct spi_driver m41t94_driver;



static int __devinit m41t94_probe(struct spi_device *spi)

{

	struct rtc_device *rtc;

	int res;



	spi->bits_per_word = 8;

	spi_setup(spi);



	res = spi_w8r8(spi, M41T94_REG_SECONDS);

	if (res < 0) {

		dev_err(&spi->dev, "not found.\n");

		return res;

	}



	rtc = rtc_device_register(m41t94_driver.driver.name,

		&spi->dev, &m41t94_rtc_ops, THIS_MODULE);

	if (IS_ERR(rtc))

		return PTR_ERR(rtc);



	dev_set_drvdata(&spi->dev, rtc);



	return 0;

}



static int __devexit m41t94_remove(struct spi_device *spi)

{

	struct rtc_device *rtc = platform_get_drvdata(spi);



	if (rtc)

		rtc_device_unregister(rtc);



	return 0;

}



static struct spi_driver m41t94_driver = {

	.driver = {

		.name	= "rtc-m41t94",

		.bus	= &spi_bus_type,

		.owner	= THIS_MODULE,

	},

	.probe	= m41t94_probe,

	.remove = __devexit_p(m41t94_remove),

};



static __init int m41t94_init(void)

{

	return spi_register_driver(&m41t94_driver);

}



module_init(m41t94_init);



static __exit void m41t94_exit(void)

{

	spi_unregister_driver(&m41t94_driver);

}



module_exit(m41t94_exit);



MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");

MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");

MODULE_LICENSE("GPL");