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path: root/drivers/rtc/rtc-m41t94.c
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Diffstat (limited to 'drivers/rtc/rtc-m41t94.c')
-rw-r--r--drivers/rtc/rtc-m41t94.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-m41t94.c b/drivers/rtc/rtc-m41t94.c
new file mode 100644
index 000000000..6803b0273
--- /dev/null
+++ b/drivers/rtc/rtc-m41t94.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for ST M41T94 SPI RTC
+ *
+ * Copyright (C) 2008 Kim B. Heino
+ */
+
+#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
+
+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);
+
+ return 0;
+}
+
+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 m41t94_probe(struct spi_device *spi)
+{
+ struct rtc_device *rtc;
+ int res;
+
+ 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");
+ return res;
+ }
+
+ rtc = devm_rtc_device_register(&spi->dev, m41t94_driver.driver.name,
+ &m41t94_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc))
+ return PTR_ERR(rtc);
+
+ spi_set_drvdata(spi, rtc);
+
+ return 0;
+}
+
+static struct spi_driver m41t94_driver = {
+ .driver = {
+ .name = "rtc-m41t94",
+ },
+ .probe = m41t94_probe,
+};
+
+module_spi_driver(m41t94_driver);
+
+MODULE_AUTHOR("Kim B. Heino <Kim.Heino@bluegiga.com>");
+MODULE_DESCRIPTION("Driver for ST M41T94 SPI RTC");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:rtc-m41t94");