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Commit 74d34d4b authored by Voss, Nikolaus's avatar Voss, Nikolaus Committed by Linus Torvalds
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rtc: add basic support for ST M41T93 SPI RTC 



Add basic support for ST m41t93 SPI RTCs.  Tested with factory-new and
with "run-in" species with and without backup batteries.

Signed-off-by: default avatarNikolaus Voss <n.voss@weinmann.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 52365230

drivers/rtc/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -385,6 +385,15 @@ comment "SPI RTC drivers" 


if SPI_MASTER



config RTC_DRV_M41T93

        tristate "ST M41T93"

        help

          If you say yes here you will get support for the

          ST M41T93 SPI RTC chip.



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

          will be called rtc-m41t93.



config RTC_DRV_M41T94

	tristate "ST M41T94"

	help

drivers/rtc/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ obj-$(CONFIG_RTC_DRV_ISL12022) += rtc-isl12022.o 
obj-$(CONFIG_RTC_DRV_JZ4740)	+= rtc-jz4740.o

obj-$(CONFIG_RTC_DRV_LPC32XX)	+= rtc-lpc32xx.o

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

obj-$(CONFIG_RTC_DRV_M41T93)	+= rtc-m41t93.o

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

obj-$(CONFIG_RTC_DRV_M48T35)	+= rtc-m48t35.o

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

drivers/rtc/rtc-m41t93.c

0 → 100644
+225 −0
Original line number Diff line number Diff line 
/*

 *

 * Driver for ST M41T93 SPI RTC

 *

 * (c) 2010 Nikolaus Voss, Weinmann Medical GmbH

 *

 * 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/bcd.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/rtc.h>

#include <linux/spi/spi.h>



#define M41T93_REG_SSEC			0

#define M41T93_REG_ST_SEC		1

#define M41T93_REG_MIN			2

#define M41T93_REG_CENT_HOUR		3

#define M41T93_REG_WDAY			4

#define M41T93_REG_DAY			5

#define M41T93_REG_MON			6

#define M41T93_REG_YEAR			7





#define M41T93_REG_ALM_HOUR_HT		0xc

#define M41T93_REG_FLAGS		0xf



#define M41T93_FLAG_ST			(1 << 7)

#define M41T93_FLAG_OF			(1 << 2)

#define M41T93_FLAG_BL			(1 << 4)

#define M41T93_FLAG_HT			(1 << 6)



static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)

{

	u8 buf[2];



	/* MSB must be '1' to write */

	buf[0] = addr | 0x80;

	buf[1] = data;



	return spi_write(spi, buf, sizeof(buf));

}



static int m41t93_set_time(struct device *dev, struct rtc_time *tm)

{

	struct spi_device *spi = to_spi_device(dev);

	u8 buf[9] = {0x80};        /* write cmd + 8 data bytes */

	u8 * const data = &buf[1]; /* ptr to first data byte */



	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);



	if (tm->tm_year < 100) {

		dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");

		return -EINVAL;

	}



	data[M41T93_REG_SSEC]		= 0;

	data[M41T93_REG_ST_SEC]		= bin2bcd(tm->tm_sec);

	data[M41T93_REG_MIN]		= bin2bcd(tm->tm_min);

	data[M41T93_REG_CENT_HOUR]	= bin2bcd(tm->tm_hour) |

						((tm->tm_year/100-1) << 6);

	data[M41T93_REG_DAY]		= bin2bcd(tm->tm_mday);

	data[M41T93_REG_WDAY]		= bin2bcd(tm->tm_wday + 1);

	data[M41T93_REG_MON]		= bin2bcd(tm->tm_mon + 1);

	data[M41T93_REG_YEAR]		= bin2bcd(tm->tm_year % 100);



	return spi_write(spi, buf, sizeof(buf));

}





static int m41t93_get_time(struct device *dev, struct rtc_time *tm)

{

	struct spi_device *spi = to_spi_device(dev);

	const u8 start_addr = 0;

	u8 buf[8];

	int century_after_1900;

	int tmp;

	int ret = 0;



	/* Check status of clock. Two states must be considered:

	   1. halt bit (HT) is set: the clock is running but update of readout

	      registers has been disabled due to power failure. This is normal

	      case after poweron. Time is valid after resetting HT bit.

	   2. oscillator fail bit (OF) is set. Oscillator has be stopped and

	      time is invalid:

	      a) OF can be immeditely reset.

	      b) OF cannot be immediately reset: oscillator has to be restarted.

	*/

	tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);

	if (tmp < 0)

		return tmp;



	if (tmp & M41T93_FLAG_HT) {

		dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");

		m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,

			       tmp & ~M41T93_FLAG_HT);

	}



	tmp = spi_w8r8(spi, M41T93_REG_FLAGS);

	if (tmp < 0)

		return tmp;



	if (tmp & M41T93_FLAG_OF) {

		ret = -EINVAL;

		dev_warn(&spi->dev, "OF bit is set, resetting.\n");

		m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);



		tmp = spi_w8r8(spi, M41T93_REG_FLAGS);

		if (tmp < 0)

			return tmp;

		else if (tmp & M41T93_FLAG_OF) {

			u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;



			dev_warn(&spi->dev,

				 "OF bit is still set, kickstarting clock.\n");

			m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);

			reset_osc &= ~M41T93_FLAG_ST;

			m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);

		}

	}



	if (tmp & M41T93_FLAG_BL)

		dev_warn(&spi->dev, "BL bit is set, replace battery.\n");



	/* read actual time/date */

	tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));

	if (tmp < 0)

		return tmp;



	tm->tm_sec	= bcd2bin(buf[M41T93_REG_ST_SEC]);

	tm->tm_min	= bcd2bin(buf[M41T93_REG_MIN]);

	tm->tm_hour	= bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);

	tm->tm_mday	= bcd2bin(buf[M41T93_REG_DAY]);

	tm->tm_mon	= bcd2bin(buf[M41T93_REG_MON]) - 1;

	tm->tm_wday	= bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;



	century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;

	tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 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);



	return ret < 0 ? ret : rtc_valid_tm(tm);

}





static const struct rtc_class_ops m41t93_rtc_ops = {

	.read_time	= m41t93_get_time,

	.set_time	= m41t93_set_time,

};



static struct spi_driver m41t93_driver;



static int __devinit m41t93_probe(struct spi_device *spi)

{

	struct rtc_device *rtc;

	int res;



	spi->bits_per_word = 8;

	spi_setup(spi);



	res = spi_w8r8(spi, M41T93_REG_WDAY);

	if (res < 0 || (res & 0xf8) != 0) {

		dev_err(&spi->dev, "not found 0x%x.\n", res);

		return -ENODEV;

	}



	rtc = rtc_device_register(m41t93_driver.driver.name,

		&spi->dev, &m41t93_rtc_ops, THIS_MODULE);

	if (IS_ERR(rtc))

		return PTR_ERR(rtc);



	dev_set_drvdata(&spi->dev, rtc);



	return 0;

}





static int __devexit m41t93_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 m41t93_driver = {

	.driver = {

		.name	= "rtc-m41t93",

		.bus	= &spi_bus_type,

		.owner	= THIS_MODULE,

	},

	.probe	= m41t93_probe,

	.remove = __devexit_p(m41t93_remove),

};



static __init int m41t93_init(void)

{

	return spi_register_driver(&m41t93_driver);

}

module_init(m41t93_init);



static __exit void m41t93_exit(void)

{

	spi_unregister_driver(&m41t93_driver);

}

module_exit(m41t93_exit);



MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");

MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");

MODULE_LICENSE("GPL");

MODULE_ALIAS("spi:rtc-m41t93");