--- /dev/null
+/*
+ *
+ * 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");
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