Add driver for STMicroelectronics M41T60 RTC

This driver is based on the driver for the M41T11.  In the intended
application, the RTC will be powered by a large capacitor, rather than a
battery.  The driver therefore checks to see whether the RTC has lost
power.  The chip's OUT bit is normally reset from its power-up state.  If
the OUT bit is read as set, or if the date and time are not valid, then the
RTC is assumed to have lost power, and its date and time are reset to
1900-01-01 00:00:00.

Support for adjusting the speed of the clock to improve accuracy is
provided through an environment variable.

Signed-off-by: Larry Johnson <lrj@acm.org>

2 files changed, 262 insertions, 0 deletions

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 1d6016e..e5ee611 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -40,6 +40,7 @@ COBJS-y += ds164x.o
 COBJS-y += ds174x.o
 COBJS-y += ds3231.o
 COBJS-y += m41t11.o
+COBJS-y += m41t60.o
 COBJS-y += max6900.o
 COBJS-y += m48t35ax.o
 COBJS-y += mc146818.o
diff --git a/drivers/rtc/m41t60.c b/drivers/rtc/m41t60.c
new file mode 100644
index 0000000..7c80143
--- /dev/null
+++ b/drivers/rtc/m41t60.c
@@ -0,0 +1,261 @@
+/*
+ * (C) Copyright 2007
+ * Larry Johnson, lrj@acm.org
+ *
+ * based on rtc/m41t11.c which is ...
+ *
+ * (C) Copyright 2002
+ * Andrew May, Viasat Inc, amay@viasat.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+/*
+ * STMicroelectronics M41T60 serial access real-time clock
+ */
+
+/* #define DEBUG 1 */
+
+#include <common.h>
+#include <command.h>
+#include <rtc.h>
+#include <i2c.h>
+
+#if defined(CONFIG_RTC_M41T60) && defined(CFG_I2C_RTC_ADDR) && \
+	defined(CONFIG_CMD_DATE)
+
+static unsigned bcd2bin(uchar n)
+{
+	return ((((n >> 4) & 0x0F) * 10) + (n & 0x0F));
+}
+
+static unsigned char bin2bcd(unsigned int n)
+{
+	return (((n / 10) << 4) | (n % 10));
+}
+
+/*
+ * Convert between century and "century bits" (CB1 and CB0).  These routines
+ * assume years are in the range 1900 - 2299.
+ */
+
+static unsigned char year2cb(unsigned const year)
+{
+	if (year < 1900 || year >= 2300)
+		printf("M41T60 RTC: year %d out of range\n", year);
+
+	return (year / 100) & 0x3;
+}
+
+static unsigned cb2year(unsigned const cb)
+{
+	return 1900 + 100 * ((cb + 1) & 0x3);
+}
+
+/*
+ * These are simple defines for the chip local to here so they aren't too
+ * verbose.  DAY/DATE aren't nice but that is how they are on the data sheet.
+ */
+#define RTC_SEC		0x0
+#define RTC_MIN		0x1
+#define RTC_HOUR	0x2
+#define RTC_DAY		0x3
+#define RTC_DATE	0x4
+#define RTC_MONTH	0x5
+#define RTC_YEAR	0x6
+
+#define RTC_REG_CNT	7
+
+#define RTC_CTRL	0x7
+
+#if defined(DEBUG)
+static void rtc_dump(char const *const label)
+{
+	uchar data[8];
+
+	if (i2c_read(CFG_I2C_RTC_ADDR, 0, 1, data, sizeof(data))) {
+		printf("I2C read failed in rtc_dump()\n");
+		return;
+	}
+	printf("RTC dump %s: %02X-%02X-%02X-%02X-%02X-%02X-%02X-%02X\n",
+	       label, data[0], data[1], data[2], data[3],
+	       data[4], data[5], data[6], data[7]);
+}
+#else
+#define rtc_dump(label)
+#endif
+
+static uchar *rtc_validate(void)
+{
+	/*
+	 * This routine uses the OUT bit and the validity of the time values to
+	 * determine whether there has been an initial power-up since the last
+	 * time the routine was run.  It assumes that the OUT bit is not being
+	 * used for any other purpose.
+	 */
+	static const uchar daysInMonth[0x13] = {
+		0x00, 0x31, 0x29, 0x31, 0x30, 0x31, 0x30, 0x31,
+		0x31, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x31, 0x30, 0x31
+	};
+	static uchar data[8];
+	uchar min, date, month, years;
+
+	rtc_dump("begin validate");
+	if (i2c_read(CFG_I2C_RTC_ADDR, 0, 1, data, sizeof(data))) {
+		printf("I2C read failed in rtc_validate()\n");
+		return 0;
+	}
+	/*
+	 * If the OUT bit is "1", there has been a loss of power, so stop the
+	 * oscillator so it can be "kick-started" as per data sheet.
+	 */
+	if (0x00 != (data[RTC_CTRL] & 0x80)) {
+		printf("M41T60 RTC clock lost power.\n");
+		data[RTC_SEC] = 0x80;
+		if (i2c_write(CFG_I2C_RTC_ADDR, RTC_SEC, 1, data, 1)) {
+			printf("I2C write failed in rtc_validate()\n");
+			return 0;
+		}
+	}
+	/*
+	 * If the oscillator is stopped or the date is invalid, then reset the
+	 * OUT bit to "0", reset the date registers, and start the oscillator.
+	 */
+	min = data[RTC_MIN] & 0x7F;
+	date = data[RTC_DATE];
+	month = data[RTC_MONTH] & 0x3F;
+	years = data[RTC_YEAR];
+	if (0x59 < data[RTC_SEC] || 0x09 < (data[RTC_SEC] & 0x0F) ||
+	    0x59 < min || 0x09 < (min & 0x0F) ||
+	    0x23 < data[RTC_HOUR] || 0x09 < (data[RTC_HOUR] & 0x0F) ||
+	    0x07 < data[RTC_DAY] || 0x00 == data[RTC_DAY] ||
+	    0x12 < month ||
+	    0x99 < years || 0x09 < (years & 0x0F) ||
+	    daysInMonth[month] < date || 0x09 < (date & 0x0F) || 0x00 == date ||
+	    (0x29 == date && 0x02 == month &&
+	     ((0x00 != (years & 0x03)) ||
+	      (0x00 == years && 0x00 != (data[RTC_MONTH] & 0xC0))))) {
+		printf("Resetting M41T60 RTC clock.\n");
+		/*
+		 * Set to 00:00:00 1900-01-01 (Monday)
+		 */
+		data[RTC_SEC] = 0x00;
+		data[RTC_MIN] &= 0x80;	/* preserve OFIE bit */
+		data[RTC_HOUR] = 0x00;
+		data[RTC_DAY] = 0x02;
+		data[RTC_DATE] = 0x01;
+		data[RTC_MONTH] = 0xC1;
+		data[RTC_YEAR] = 0x00;
+		data[RTC_CTRL] &= 0x7F;	/* reset OUT bit */
+
+		if (i2c_write(CFG_I2C_RTC_ADDR, 0, 1, data, sizeof(data))) {
+			printf("I2C write failed in rtc_validate()\n");
+			return 0;
+		}
+	}
+	return data;
+}
+
+void rtc_get(struct rtc_time *tmp)
+{
+	uchar const *const data = rtc_validate();
+
+	if (!data)
+		return;
+
+	tmp->tm_sec = bcd2bin(data[RTC_SEC] & 0x7F);
+	tmp->tm_min = bcd2bin(data[RTC_MIN] & 0x7F);
+	tmp->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3F);
+	tmp->tm_mday = bcd2bin(data[RTC_DATE] & 0x3F);
+	tmp->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1F);
+	tmp->tm_year = cb2year(data[RTC_MONTH] >> 6) + bcd2bin(data[RTC_YEAR]);
+	tmp->tm_wday = bcd2bin(data[RTC_DAY] & 0x07) - 1;
+	tmp->tm_yday = 0;
+	tmp->tm_isdst = 0;
+
+	debug("Get DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
+	      tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
+	      tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+}
+
+void rtc_set(struct rtc_time *tmp)
+{
+	uchar *const data = rtc_validate();
+
+	if (!data)
+		return;
+
+	debug("Set DATE: %4d-%02d-%02d (wday=%d)  TIME: %2d:%02d:%02d\n",
+	      tmp->tm_year, tmp->tm_mon, tmp->tm_mday, tmp->tm_wday,
+	      tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
+
+	data[RTC_SEC] = (data[RTC_SEC] & 0x80) | (bin2bcd(tmp->tm_sec) & 0x7F);
+	data[RTC_MIN] = (data[RTC_MIN] & 0X80) | (bin2bcd(tmp->tm_min) & 0X7F);
+	data[RTC_HOUR] = bin2bcd(tmp->tm_hour) & 0x3F;
+	data[RTC_DATE] = bin2bcd(tmp->tm_mday) & 0x3F;
+	data[RTC_MONTH] = bin2bcd(tmp->tm_mon) & 0x1F;
+	data[RTC_YEAR] = bin2bcd(tmp->tm_year % 100);
+	data[RTC_MONTH] |= year2cb(tmp->tm_year) << 6;
+	data[RTC_DAY] = bin2bcd(tmp->tm_wday + 1) & 0x07;
+	if (i2c_write(CFG_I2C_RTC_ADDR, 0, 1, data, RTC_REG_CNT)) {
+		printf("I2C write failed in rtc_set()\n");
+		return;
+	}
+}
+
+void rtc_reset(void)
+{
+	uchar *const data = rtc_validate();
+	char const *const s = getenv("rtccal");
+
+	if (!data)
+		return;
+
+	rtc_dump("begin reset");
+	/*
+	 * If environmental variable "rtccal" is present, it must be a hex value
+	 * between 0x00 and 0x3F, inclusive.  The five least-significan bits
+	 * represent the calibration magnitude, and the sixth bit the sign bit.
+	 * If these do not match the contents of the hardware register, that
+	 * register is updated.  The value 0x00 imples no correction.  Consult
+	 * the M41T60 documentation for further details.
+	 */
+	if (s) {
+		unsigned long const l = simple_strtoul(s, 0, 16);
+
+		if (l <= 0x3F) {
+			if ((data[RTC_CTRL] & 0x3F) != l) {
+				printf("Setting RTC calibration to 0x%02X\n",
+				       l);
+				data[RTC_CTRL] &= 0xC0;
+				data[RTC_CTRL] |= (uchar) l;
+			}
+		} else
+			printf("environment parameter \"rtccal\" not valid: "
+			       "ignoring\n");
+	}
+	/*
+	 * Turn off frequency test.
+	 */
+	data[RTC_CTRL] &= 0xBF;
+	if (i2c_write(CFG_I2C_RTC_ADDR, RTC_CTRL, 1, data + RTC_CTRL, 1)) {
+		printf("I2C write failed in rtc_reset()\n");
+		return;
+	}
+	rtc_dump("end reset");
+}
+#endif /* CONFIG_RTC_M41T60 && CFG_I2C_RTC_ADDR && CONFIG_CMD_DATE */