rtc: add NXP PCF2127 support (i2c)

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index b983813..8009e5d 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -313,6 +313,15 @@  config RTC_DRV_PALMAS
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-palma.
 
+config RTC_DRV_PCF2127
+	tristate "NXP PCF2127"
+	help
+	  If you say yes here you get support for the NXP PCF2127/29 RTC
+	  chips.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-pcf2127.
+
 config RTC_DRV_PCF8523
 	tristate "NXP PCF8523"
 	help
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index c33f86f..994a2fa 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -83,6 +83,7 @@  obj-$(CONFIG_RTC_DRV_NUC900)	+= rtc-nuc900.o
 obj-$(CONFIG_RTC_DRV_OMAP)	+= rtc-omap.o
 obj-$(CONFIG_RTC_DRV_PALMAS)	+= rtc-palmas.o
 obj-$(CONFIG_RTC_DRV_PCAP)	+= rtc-pcap.o
+obj-$(CONFIG_RTC_DRV_PCF2127)	+= rtc-pcf2127.o
 obj-$(CONFIG_RTC_DRV_PCF8523)	+= rtc-pcf8523.o
 obj-$(CONFIG_RTC_DRV_PCF8563)	+= rtc-pcf8563.o
 obj-$(CONFIG_RTC_DRV_PCF8583)	+= rtc-pcf8583.o
diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
new file mode 100644
index 0000000..4d44379
--- /dev/null
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -0,0 +1,243 @@ 
+/*
+ * An I2C driver for the NXP PCF2127 RTC
+ * Copyright 2013 Til-Technologies
+ *
+ * Author: Renaud Cerrato <r.cerrato@til-technologies.fr>
+ *
+ * based on the other drivers in this same directory.
+ *
+ * http://www.nxp.com/documents/data_sheet/PCF2127AT.pdf
+ *
+ * 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/i2c.h>
+#include <linux/bcd.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+#define DRV_VERSION "0.0.1"
+
+#define PCF2127_REG_CTRL1       (0x00)  /* Control Register 1 */
+#define PCF2127_REG_CTRL2       (0x01)  /* Control Register 2 */
+#define PCF2127_REG_CTRL3       (0x02)  /* Control Register 3 */
+#define PCF2127_REG_SC          (0x03)  /* datetime */
+#define PCF2127_REG_MN          (0x04)
+#define PCF2127_REG_HR          (0x05)
+#define PCF2127_REG_DM          (0x06)
+#define PCF2127_REG_DW          (0x07)
+#define PCF2127_REG_MO          (0x08)
+#define PCF2127_REG_YR          (0x09)
+
+static struct i2c_driver pcf2127_driver;
+
+struct pcf2127 {
+	struct rtc_device *rtc;
+	int voltage_low; /* incicates if a low_voltage was detected */
+};
+
+/*
+ * In the routines that deal directly with the pcf2127 hardware, we use
+ * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
+ */
+static int pcf2127_get_datetime(struct i2c_client *client, struct rtc_time *tm)
+{
+	struct pcf2127 *pcf2127 = i2c_get_clientdata(client);
+	unsigned char buf[10] = { PCF2127_REG_CTRL1 };
+
+	/* read registers */
+	if (i2c_master_send(client, buf, 1) != 1 ||
+		i2c_master_recv(client, buf, sizeof(buf)) != sizeof(buf)) {
+		dev_err(&client->dev, "%s: read error\n", __func__);
+		return -EIO;
+	}
+
+	if (buf[PCF2127_REG_CTRL3] & 0x04) {
+		pcf2127->voltage_low = 1;
+		dev_info(&client->dev,
+			"low voltage detected, date/time is not reliable.\n");
+	}
+
+	dev_dbg(&client->dev,
+		"%s: raw data is cr1=%02x, cr2=%02x, cr3=%02x, "
+		"sec=%02x, min=%02x, hr=%02x, "
+		"mday=%02x, wday=%02x, mon=%02x, year=%02x\n",
+		__func__,
+		buf[0], buf[1], buf[2],
+		buf[3], buf[4], buf[5],
+		buf[6], buf[7], buf[8], buf[9]);
+
+
+	tm->tm_sec = bcd2bin(buf[PCF2127_REG_SC] & 0x7F);
+	tm->tm_min = bcd2bin(buf[PCF2127_REG_MN] & 0x7F);
+	tm->tm_hour = bcd2bin(buf[PCF2127_REG_HR] & 0x3F); /* rtc hr 0-23 */
+	tm->tm_mday = bcd2bin(buf[PCF2127_REG_DM] & 0x3F);
+	tm->tm_wday = buf[PCF2127_REG_DW] & 0x07;
+	tm->tm_mon = bcd2bin(buf[PCF2127_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
+	tm->tm_year = bcd2bin(buf[PCF2127_REG_YR]);
+	if (tm->tm_year < 70)
+		tm->tm_year += 100;	/* assume we are in 1970...2069 */
+
+	dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	/* the clock can give out invalid datetime, but we cannot return
+	 * -EINVAL otherwise hwclock will refuse to set the time on bootup.
+	 */
+	if (rtc_valid_tm(tm) < 0)
+		dev_err(&client->dev, "retrieved date/time is not valid.\n");
+
+	return 0;
+}
+
+static int pcf2127_set_datetime(struct i2c_client *client, struct rtc_time *tm)
+{
+	struct pcf2127 *pcf2127 = i2c_get_clientdata(client);
+	unsigned char buf[8];
+	int i = 0, err;
+
+	dev_dbg(&client->dev, "%s: secs=%d, mins=%d, hours=%d, "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	/* start register address */
+	buf[i++] = PCF2127_REG_SC;
+
+	/* hours, minutes and seconds */
+	buf[i++] = bin2bcd(tm->tm_sec);
+	buf[i++] = bin2bcd(tm->tm_min);
+	buf[i++] = bin2bcd(tm->tm_hour);
+	buf[i++] = bin2bcd(tm->tm_mday);
+	buf[i++] = tm->tm_wday & 0x07;
+
+	/* month, 1 - 12 */
+	buf[i++] = bin2bcd(tm->tm_mon + 1);
+
+	/* year */
+	buf[i++] = bin2bcd(tm->tm_year % 100);
+
+	/* write register's data */
+	err = i2c_master_send(client, buf, i);
+	if (err != i) {
+		dev_err(&client->dev,
+			"%s: err=%d", __func__, err);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_RTC_INTF_DEV
+static int pcf2127_rtc_ioctl(struct device *dev,
+				unsigned int cmd, unsigned long arg)
+{
+	struct pcf2127 *pcf2127 = i2c_get_clientdata(to_i2c_client(dev));
+	struct rtc_time tm;
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		if (pcf2127->voltage_low)
+			dev_info(dev, "low voltage detected, date/time is not reliable.\n");
+
+		if (copy_to_user((void __user *)arg, &pcf2127->voltage_low,
+					sizeof(int)))
+			return -EFAULT;
+		return 0;
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+#else
+#define pcf2127_rtc_ioctl NULL
+#endif
+
+static int pcf2127_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	return pcf2127_get_datetime(to_i2c_client(dev), tm);
+}
+
+static int pcf2127_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return pcf2127_set_datetime(to_i2c_client(dev), tm);
+}
+
+static const struct rtc_class_ops pcf2127_rtc_ops = {
+	.ioctl		= pcf2127_rtc_ioctl,
+	.read_time	= pcf2127_rtc_read_time,
+	.set_time	= pcf2127_rtc_set_time,
+};
+
+static int pcf2127_probe(struct i2c_client *client,
+				const struct i2c_device_id *id)
+{
+	struct pcf2127 *pcf2127;
+
+	dev_dbg(&client->dev, "%s\n", __func__);
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	pcf2127 = devm_kzalloc(&client->dev, sizeof(struct pcf2127),
+				GFP_KERNEL);
+	if (!pcf2127)
+		return -ENOMEM;
+
+	dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
+
+	i2c_set_clientdata(client, pcf2127);
+
+	pcf2127->rtc = devm_rtc_device_register(&client->dev,
+				pcf2127_driver.driver.name,
+				&pcf2127_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(pcf2127->rtc))
+		return PTR_ERR(pcf2127->rtc);
+
+	return 0;
+}
+
+static int pcf2127_remove(struct i2c_client *client)
+{
+	return 0;
+}
+
+static const struct i2c_device_id pcf2127_id[] = {
+	{ "pcf2127", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, pcf2127_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id pcf2127_of_match[] = {
+	{ .compatible = "nxp,pcf2127" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pcf2127_of_match);
+#endif
+
+static struct i2c_driver pcf2127_driver = {
+	.driver		= {
+		.name	= "rtc-pcf2127",
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(pcf2127_of_match),
+	},
+	.probe		= pcf2127_probe,
+	.remove		= pcf2127_remove,
+	.id_table	= pcf2127_id,
+};
+
+module_i2c_driver(pcf2127_driver);
+
+MODULE_AUTHOR("Renaud Cerrato <r.cerrato@til-technologies.fr>");
+MODULE_DESCRIPTION("NXP PCF2127 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);