[U-Boot-Users] [PATCH] Re: Add support for M41T60 serial access real-time clock

[Larry Johnson <lrj@arlinx.com>]

Based on the comment I received, I have made some modifications to the
patch I submitted to add support for the M41T60 RTC to u-boot.  The main
changes are to fix and amplify the comments, but I have also changed the
code so it will not modify the OFIE bit on a power up or invalid time.

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

diff -Naur a/rtc/m41t60.c b/rtc/m41t60.c
--- a/rtc/m41t60.c	1969-12-31 19:00:00.000000000 -0500
+++ b/rtc/m41t60.c	2007-06-22 19:05:00.000000000 -0400
@@ -0,0 +1,237 @@
+/*
+ * (C) Copyright 2007
+ * Larry Johnson, lrj at acm.org
+ *
+ * based on rtc/m41t11.c which is ...
+ *
+ * (C) Copyright 2002
+ * Andrew May, Viasat Inc, amay at 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) && \
+	(CONFIG_COMMANDS & CFG_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_YEARS	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 /* !defined(DEBUG) */
+#define rtc_dump(label)
+#endif /* defined(DEBUG) */
+
+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_YEARS];
+	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_YEARS] = 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_YEARS]);
+	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_YEARS] = 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();
+
+	if (!data) {
+		return;
+	}
+	rtc_dump("begin reset");
+	/*
+	 * 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 && CFG_CMD_DATE */
diff -Naur a/rtc/Makefile b/rtc/Makefile
--- a/rtc/Makefile	2007-06-12 08:23:00.000000000 -0400
+++ b/rtc/Makefile	2007-06-22 19:05:00.000000000 -0400
@@ -31,7 +31,8 @@
 	  bf5xx_rtc.o ds12887.o ds1302.o ds1306.o ds1307.o \
 	  ds1337.o ds1374.o ds1556.o ds164x.o ds174x.o ds3231.o \
 	  m41t11.o max6900.o m48t35ax.o mc146818.o mk48t59.o \
-	  mpc5xxx.o mpc8xx.o pcf8563.o s3c24x0_rtc.o rs5c372.o
+	  mpc5xxx.o mpc8xx.o pcf8563.o s3c24x0_rtc.o rs5c372.o \
+	  m41t60.o
 
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))

-- Best regards, Larry