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Subject[PATCH] add support for ST M41T94 SPI RTC (patch rev. 2)
This patch adds kernel driver for M41T94 RTC chip connected via SPI.
I've tested it on two different AT91-based hardwares.

This is second revision of the patch: support for century bit added,
some comments made by Alessandro Zummo fixed.

Signed-off-by: Kim B. Heino <Kim.Heino@bluegiga.com>


diff -urN orig/drivers/rtc/Kconfig linux-2.6.25/drivers/rtc/Kconfig
--- orig/drivers/rtc/Kconfig 2008-04-17 05:49:44.000000000 +0300
+++ linux-2.6.25/drivers/rtc/Kconfig 2008-05-14 16:58:58.000000000 +0300
@@ -266,6 +266,15 @@

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
diff -urN orig/drivers/rtc/Makefile linux-2.6.25/drivers/rtc/Makefile
--- orig/drivers/rtc/Makefile 2008-04-17 05:49:44.000000000 +0300
+++ linux-2.6.25/drivers/rtc/Makefile 2008-05-14 16:58:58.000000000 +0300
@@ -33,6 +33,7 @@
obj-$(CONFIG_RTC_DRV_EP93XX) += rtc-ep93xx.o
obj-$(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
diff -urN orig/drivers/rtc/rtc-m41t94.c linux-2.6.25/drivers/rtc/rtc-m41t94.c
--- orig/drivers/rtc/rtc-m41t94.c 1970-01-01 02:00:00.000000000 +0200
+++ linux-2.6.25/drivers/rtc/rtc-m41t94.c 2008-05-14 16:59:09.000000000 +0300
@@ -0,0 +1,188 @@
+/*
+ * 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
+
+struct m41t94 {
+ struct rtc_device *rtc;
+};
+
+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;
+ struct m41t94 *m41t94;
+ int res;
+
+ m41t94 = kzalloc(sizeof(struct m41t94), GFP_KERNEL);
+ if (!m41t94)
+ return -ENOMEM;
+ dev_set_drvdata(&spi->dev, m41t94);
+
+ 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");
+ kfree(m41t94);
+ return res;
+ }
+
+ rtc = rtc_device_register(m41t94_driver.driver.name,
+ &spi->dev, &m41t94_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc)) {
+ kfree(m41t94);
+ return PTR_ERR(rtc);
+ }
+
+ m41t94->rtc = rtc;
+
+ return 0;
+}
+
+static int __devexit m41t94_remove(struct spi_device *spi)
+{
+ struct m41t94 *m41t94 = platform_get_drvdata(spi);
+ struct rtc_device *rtc = m41t94->rtc;
+
+ if (rtc)
+ rtc_device_unregister(rtc);
+ kfree(m41t94);
+
+ 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");

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