rtc: add device driver for Dallas DS3234 SPI RTC chip

Add support for the Dallas DS3234 chip - extremely accurate SPI bus RTC
with integrated crystal and SRAM.

[akpm@linux-foundation.org: don't use BIN2BCD/BCD2BIN]
Signed-off-by: Dennis Aberilla <denzzzhome@yahoo.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 300 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index f3d7fd3406a6..16bc33cbadf5 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -319,6 +319,15 @@ config RTC_DRV_RS5C348
           This driver can also be built as a module. If so, the module
           will be called rtc-rs5c348.
 
+config RTC_DRV_DS3234
+        tristate "Maxim/Dallas DS3234"
+        help
+          If you say yes here you get support for the
+          Maxim/Dallas DS3234 SPI RTC chip.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-ds3234.
+
 endif # SPI_MASTER
 
 comment "Platform RTC drivers"
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 37a71b727262..d05928b3ca94 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_RTC_DRV_DS1511)	+= rtc-ds1511.o
 obj-$(CONFIG_RTC_DRV_DS1553)    += rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_DS1672)    += rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_DS1742)    += rtc-ds1742.o
+obj-$(CONFIG_RTC_DRV_DS3234)    += rtc-ds3234.o
 obj-$(CONFIG_RTC_DRV_EP93XX)    += rtc-ep93xx.o
 obj-$(CONFIG_RTC_DRV_FM3130)    += rtc-fm3130.o
 obj-$(CONFIG_RTC_DRV_ISL1208)   += rtc-isl1208.o
diff --git a/drivers/rtc/rtc-ds3234.c b/drivers/rtc/rtc-ds3234.c
new file mode 100644
index 000000000000..37d131d03f33
--- /dev/null
+++ b/drivers/rtc/rtc-ds3234.c
@@ -0,0 +1,290 @@
+/* drivers/rtc/rtc-ds3234.c
+ *
+ * Driver for Dallas Semiconductor (DS3234) SPI RTC with Integrated Crystal
+ * and SRAM.
+ *
+ * Copyright (C) 2008 MIMOMax Wireless Ltd.
+ *
+ * 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.
+ *
+ * Changelog:
+ *
+ * 07-May-2008: Dennis Aberilla <denzzzhome@yahoo.com>
+ *              - Created based on the max6902 code. Only implements the
+ *                date/time keeping functions; no SRAM yet.
+ */
+
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+#include <linux/bcd.h>
+
+#define DS3234_REG_SECONDS      0x00
+#define DS3234_REG_MINUTES      0x01
+#define DS3234_REG_HOURS        0x02
+#define DS3234_REG_DAY          0x03
+#define DS3234_REG_DATE         0x04
+#define DS3234_REG_MONTH        0x05
+#define DS3234_REG_YEAR         0x06
+#define DS3234_REG_CENTURY      (1 << 7) /* Bit 7 of the Month register */
+
+#define DS3234_REG_CONTROL      0x0E
+#define DS3234_REG_CONT_STAT    0x0F
+
+#undef DS3234_DEBUG
+
+struct ds3234 {
+        struct rtc_device *rtc;
+        u8 buf[8]; /* Burst read: addr + 7 regs */
+        u8 tx_buf[2];
+        u8 rx_buf[2];
+};
+
+static void ds3234_set_reg(struct device *dev, unsigned char address,
+                                unsigned char data)
+{
+        struct spi_device *spi = to_spi_device(dev);
+        unsigned char buf[2];
+
+        /* MSB must be '1' to indicate write */
+        buf[0] = address | 0x80;
+        buf[1] = data;
+
+        spi_write(spi, buf, 2);
+}
+
+static int ds3234_get_reg(struct device *dev, unsigned char address,
+                                unsigned char *data)
+{
+        struct spi_device *spi = to_spi_device(dev);
+        struct ds3234 *chip = dev_get_drvdata(dev);
+        struct spi_message message;
+        struct spi_transfer xfer;
+        int status;
+
+        if (!data)
+                return -EINVAL;
+
+        /* Build our spi message */
+        spi_message_init(&message);
+        memset(&xfer, 0, sizeof(xfer));
+
+        /* Address + dummy tx byte */
+        xfer.len = 2;
+        xfer.tx_buf = chip->tx_buf;
+        xfer.rx_buf = chip->rx_buf;
+
+        chip->tx_buf[0] = address;
+        chip->tx_buf[1] = 0xff;
+
+        spi_message_add_tail(&xfer, &message);
+
+        /* do the i/o */
+        status = spi_sync(spi, &message);
+        if (status == 0)
+                status = message.status;
+        else
+                return status;
+
+        *data = chip->rx_buf[1];
+
+        return status;
+}
+
+static int ds3234_get_datetime(struct device *dev, struct rtc_time *dt)
+{
+        struct spi_device *spi = to_spi_device(dev);
+        struct ds3234 *chip = dev_get_drvdata(dev);
+        struct spi_message message;
+        struct spi_transfer xfer;
+        int status;
+
+        /* build the message */
+        spi_message_init(&message);
+        memset(&xfer, 0, sizeof(xfer));
+        xfer.len = 1 + 7;       /* Addr + 7 registers */
+        xfer.tx_buf = chip->buf;
+        xfer.rx_buf = chip->buf;
+        chip->buf[0] = 0x00;    /* Start address */
+        spi_message_add_tail(&xfer, &message);
+
+        /* do the i/o */
+        status = spi_sync(spi, &message);
+        if (status == 0)
+                status = message.status;
+        else
+                return status;
+
+        /* Seconds, Minutes, Hours, Day, Date, Month, Year */
+        dt->tm_sec      = bcd2bin(chip->buf[1]);
+        dt->tm_min      = bcd2bin(chip->buf[2]);
+        dt->tm_hour     = bcd2bin(chip->buf[3] & 0x3f);
+        dt->tm_wday     = bcd2bin(chip->buf[4]) - 1; /* 0 = Sun */
+        dt->tm_mday     = bcd2bin(chip->buf[5]);
+        dt->tm_mon      = bcd2bin(chip->buf[6] & 0x1f) - 1; /* 0 = Jan */
+        dt->tm_year     = bcd2bin(chip->buf[7] & 0xff) + 100; /* Assume 20YY */
+
+#ifdef DS3234_DEBUG
+        dev_dbg(dev, "\n%s : Read RTC values\n", __func__);
+        dev_dbg(dev, "tm_hour: %i\n", dt->tm_hour);
+        dev_dbg(dev, "tm_min : %i\n", dt->tm_min);
+        dev_dbg(dev, "tm_sec : %i\n", dt->tm_sec);
+        dev_dbg(dev, "tm_wday: %i\n", dt->tm_wday);
+        dev_dbg(dev, "tm_mday: %i\n", dt->tm_mday);
+        dev_dbg(dev, "tm_mon : %i\n", dt->tm_mon);
+        dev_dbg(dev, "tm_year: %i\n", dt->tm_year);
+#endif
+
+        return 0;
+}
+
+static int ds3234_set_datetime(struct device *dev, struct rtc_time *dt)
+{
+#ifdef DS3234_DEBUG
+        dev_dbg(dev, "\n%s : Setting RTC values\n", __func__);
+        dev_dbg(dev, "tm_sec : %i\n", dt->tm_sec);
+        dev_dbg(dev, "tm_min : %i\n", dt->tm_min);
+        dev_dbg(dev, "tm_hour: %i\n", dt->tm_hour);
+        dev_dbg(dev, "tm_wday: %i\n", dt->tm_wday);
+        dev_dbg(dev, "tm_mday: %i\n", dt->tm_mday);
+        dev_dbg(dev, "tm_mon : %i\n", dt->tm_mon);
+        dev_dbg(dev, "tm_year: %i\n", dt->tm_year);
+#endif
+
+        ds3234_set_reg(dev, DS3234_REG_SECONDS, bin2bcd(dt->tm_sec));
+        ds3234_set_reg(dev, DS3234_REG_MINUTES, bin2bcd(dt->tm_min));
+        ds3234_set_reg(dev, DS3234_REG_HOURS, bin2bcd(dt->tm_hour) & 0x3f);
+
+        /* 0 = Sun */