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.

[[e-mail]: don't use BIN2BCD/BCD2BIN]
Signed-off-by: Dennis Aberilla <[e-mail]>
Signed-off-by: Alessandro Zummo <[e-mail]>
Cc: David Brownell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/Kconfig

···
 	  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"

drivers/rtc/Makefile

···
 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

drivers/rtc/rtc-ds3234.c

···
+/* 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 <[e-mail]>
+ *		- 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 */
+	ds3234_set_reg(dev, DS3234_REG_DAY, bin2bcd(dt->tm_wday + 1));
+	ds3234_set_reg(dev, DS3234_REG_DATE, bin2bcd(dt->tm_mday));
+
+	/* 0 = Jan */
+	ds3234_set_reg(dev, DS3234_REG_MONTH, bin2bcd(dt->tm_mon + 1));
+
+	/* Assume 20YY although we just want to make sure not to go negative. */
+	if (dt->tm_year > 100)
+		dt->tm_year -= 100;
+
+	ds3234_set_reg(dev, DS3234_REG_YEAR, bin2bcd(dt->tm_year));
+
+	return 0;
+}
+
+static int ds3234_read_time(struct device *dev, struct rtc_time *tm)
+{
+	return ds3234_get_datetime(dev, tm);
+}
+
+static int ds3234_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return ds3234_set_datetime(dev, tm);
+}
+
+static const struct rtc_class_ops ds3234_rtc_ops = {
+	.read_time	= ds3234_read_time,
+	.set_time	= ds3234_set_time,
+};
+
+static int ds3234_probe(struct spi_device *spi)
+{
+	struct rtc_device *rtc;
+	unsigned char tmp;
+	struct ds3234 *chip;
+	int res;
+
+	rtc = rtc_device_register("ds3234",
+				&spi->dev, &ds3234_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	spi->mode = SPI_MODE_3;
+	spi->bits_per_word = 8;
+	spi_setup(spi);
+
+	chip = kzalloc(sizeof(struct ds3234), GFP_KERNEL);
+	if (!chip) {
+		rtc_device_unregister(rtc);
+		return -ENOMEM;
+	}
+	chip->rtc = rtc;
+	dev_set_drvdata(&spi->dev, chip);
+
+	res = ds3234_get_reg(&spi->dev, DS3234_REG_SECONDS, &tmp);
+	if (res) {
+		rtc_device_unregister(rtc);
+		return res;
+	}
+
+	/* Control settings
+	 *
+	 * CONTROL_REG
+	 * BIT 7	6	5	4	3	2	1	0
+	 *     EOSC	BBSQW	CONV	RS2	RS1	INTCN	A2IE	A1IE
+	 *
+	 *     0	0	0	1	1	1	0	0
+	 *
+	 * CONTROL_STAT_REG
+	 * BIT 7	6	5	4	3	2	1	0
+	 *     OSF	BB32kHz	CRATE1	CRATE0	EN32kHz	BSY	A2F	A1F
+	 *
+	 *     1	0	0	0	1	0	0	0
+	 */
+	ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
+	ds3234_set_reg(&spi->dev, DS3234_REG_CONTROL, tmp & 0x1c);
+
+	ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
+	ds3234_set_reg(&spi->dev, DS3234_REG_CONT_STAT, tmp & 0x88);
+
+	/* Print our settings */
+	ds3234_get_reg(&spi->dev, DS3234_REG_CONTROL, &tmp);
+	dev_info(&spi->dev, "Control Reg: 0x%02x\n", tmp);
+
+	ds3234_get_reg(&spi->dev, DS3234_REG_CONT_STAT, &tmp);
+	dev_info(&spi->dev, "Ctrl/Stat Reg: 0x%02x\n", tmp);
+
+	return 0;
+}
+
+static int __exit ds3234_remove(struct spi_device *spi)
+{
+	struct ds3234 *chip = platform_get_drvdata(spi);
+	struct rtc_device *rtc = chip->rtc;
+
+	if (rtc)
+		rtc_device_unregister(rtc);
+
+	kfree(chip);
+
+	return 0;
+}
+
+static struct spi_driver ds3234_driver = {
+	.driver = {
+		.name	 = "ds3234",
+		.bus	= &spi_bus_type,
+		.owner	= THIS_MODULE,
+	},
+	.probe	 = ds3234_probe,
+	.remove = __devexit_p(ds3234_remove),
+};
+
+static __init int ds3234_init(void)
+{
+	printk(KERN_INFO "DS3234 SPI RTC Driver\n");
+	return spi_register_driver(&ds3234_driver);
+}
+module_init(ds3234_init);
+
+static __exit void ds3234_exit(void)
+{
+	spi_unregister_driver(&ds3234_driver);
+}
+module_exit(ds3234_exit);
+
+MODULE_DESCRIPTION("DS3234 SPI RTC driver");
+MODULE_AUTHOR("Dennis Aberilla <[e-mail]>");
+MODULE_LICENSE("GPL");