rtc: add rtc-abx80x, a driver for the Abracon AB x80x i2c rtc

This is a basic driver for the ultra-low-power Abracon AB x80x series of RTC
chips. It supports in particular, the supersets AB0805 and AB1805.
It allows reading and writing the time, and enables the supercapacitor/
battery charger.

[arnd@arndb.de: abx805 depends on i2c]
[alexandre.belloni@free-electrons.com: renam buffer from date to buf in abx80x_rtc_read_time()]
Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -164,6 +164,16 @@ config RTC_DRV_ABB5ZES3
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ab-b5ze-s3.
 
+config RTC_DRV_ABX80X
+	tristate "Abracon ABx80x"
+	help
+	  If you say yes here you get support for Abracon AB080X and AB180X
+	  families of ultra-low-power  battery- and capacitor-backed real-time
+	  clock chips.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-abx80x.
+
 config RTC_DRV_AS3722
 	tristate "ams AS3722 RTC driver"
 	depends on MFD_AS3722

drivers/rtc/Makefile

@@ -25,6 +25,7 @@ obj-$(CONFIG_RTC_DRV_88PM80X)	+= rtc-88pm80x.o
 obj-$(CONFIG_RTC_DRV_AB3100)	+= rtc-ab3100.o
 obj-$(CONFIG_RTC_DRV_AB8500)	+= rtc-ab8500.o
 obj-$(CONFIG_RTC_DRV_ABB5ZES3)	+= rtc-ab-b5ze-s3.o
+obj-$(CONFIG_RTC_DRV_ABX80X)	+= rtc-abx80x.o
 obj-$(CONFIG_RTC_DRV_ARMADA38X)	+= rtc-armada38x.o
 obj-$(CONFIG_RTC_DRV_AS3722)	+= rtc-as3722.o
 obj-$(CONFIG_RTC_DRV_AT32AP700X)+= rtc-at32ap700x.o

drivers/rtc/rtc-abx80x.c

@@ -0,0 +1,307 @@
+/*
+ * A driver for the I2C members of the Abracon AB x8xx RTC family,
+ * and compatible: AB 1805 and AB 0805
+ *
+ * Copyright 2014-2015 Macq S.A.
+ *
+ * Author: Philippe De Muyter <phdm@macqel.be>
+ * Author: Alexandre Belloni <alexandre.belloni@free-electrons.com>
+ *
+ * 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/i2c.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+
+#define ABX8XX_REG_HTH		0x00
+#define ABX8XX_REG_SC		0x01
+#define ABX8XX_REG_MN		0x02
+#define ABX8XX_REG_HR		0x03
+#define ABX8XX_REG_DA		0x04
+#define ABX8XX_REG_MO		0x05
+#define ABX8XX_REG_YR		0x06
+#define ABX8XX_REG_WD		0x07
+
+#define ABX8XX_REG_CTRL1	0x10
+#define ABX8XX_CTRL_WRITE	BIT(1)
+#define ABX8XX_CTRL_12_24	BIT(6)
+
+#define ABX8XX_REG_CFG_KEY	0x1f
+#define ABX8XX_CFG_KEY_MISC	0x9d
+
+#define ABX8XX_REG_ID0		0x28
+
+#define ABX8XX_REG_TRICKLE	0x20
+#define ABX8XX_TRICKLE_CHARGE_ENABLE	0xa0
+#define ABX8XX_TRICKLE_STANDARD_DIODE	0x8
+#define ABX8XX_TRICKLE_SCHOTTKY_DIODE	0x4
+
+static u8 trickle_resistors[] = {0, 3, 6, 11};
+
+enum abx80x_chip {AB0801, AB0803, AB0804, AB0805,
+	AB1801, AB1803, AB1804, AB1805, ABX80X};
+
+struct abx80x_cap {
+	u16 pn;
+	bool has_tc;
+};
+
+static struct abx80x_cap abx80x_caps[] = {
+	[AB0801] = {.pn = 0x0801},
+	[AB0803] = {.pn = 0x0803},
+	[AB0804] = {.pn = 0x0804, .has_tc = true},
+	[AB0805] = {.pn = 0x0805, .has_tc = true},
+	[AB1801] = {.pn = 0x1801},
+	[AB1803] = {.pn = 0x1803},
+	[AB1804] = {.pn = 0x1804, .has_tc = true},
+	[AB1805] = {.pn = 0x1805, .has_tc = true},
+	[ABX80X] = {.pn = 0}
+};
+
+static struct i2c_driver abx80x_driver;
+
+static int abx80x_enable_trickle_charger(struct i2c_client *client,
+					 u8 trickle_cfg)
+{
+	int err;
+
+	/*
+	 * Write the configuration key register to enable access to the Trickle
+	 * register
+	 */
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+					ABX8XX_CFG_KEY_MISC);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write configuration key\n");
+		return -EIO;
+	}
+
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_TRICKLE,
+					ABX8XX_TRICKLE_CHARGE_ENABLE |
+					trickle_cfg);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write trickle register\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int abx80x_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char buf[8];
+	int err;
+
+	err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_HTH,
+					    sizeof(buf), buf);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to read date\n");
+		return -EIO;
+	}
+
+	tm->tm_sec = bcd2bin(buf[ABX8XX_REG_SC] & 0x7F);
+	tm->tm_min = bcd2bin(buf[ABX8XX_REG_MN] & 0x7F);
+	tm->tm_hour = bcd2bin(buf[ABX8XX_REG_HR] & 0x3F);
+	tm->tm_wday = buf[ABX8XX_REG_WD] & 0x7;
+	tm->tm_mday = bcd2bin(buf[ABX8XX_REG_DA] & 0x3F);
+	tm->tm_mon = bcd2bin(buf[ABX8XX_REG_MO] & 0x1F) - 1;
+	tm->tm_year = bcd2bin(buf[ABX8XX_REG_YR]) + 100;
+
+	err = rtc_valid_tm(tm);
+	if (err < 0)
+		dev_err(&client->dev, "retrieved date/time is not valid.\n");
+
+	return err;
+}
+
+static int abx80x_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char buf[8];
+	int err;
+
+	if (tm->tm_year < 100)
+		return -EINVAL;
+
+	buf[ABX8XX_REG_HTH] = 0;
+	buf[ABX8XX_REG_SC] = bin2bcd(tm->tm_sec);
+	buf[ABX8XX_REG_MN] = bin2bcd(tm->tm_min);
+	buf[ABX8XX_REG_HR] = bin2bcd(tm->tm_hour);
+	buf[ABX8XX_REG_DA] = bin2bcd(tm->tm_mday);
+	buf[ABX8XX_REG_MO] = bin2bcd(tm->tm_mon + 1);
+	buf[ABX8XX_REG_YR] = bin2bcd(tm->tm_year - 100);
+	buf[ABX8XX_REG_WD] = tm->tm_wday;
+
+	err = i2c_smbus_write_i2c_block_data(client, ABX8XX_REG_HTH,
+					     sizeof(buf), buf);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write to date registers\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static const struct rtc_class_ops abx80x_rtc_ops = {
+	.read_time	= abx80x_rtc_read_time,
+	.set_time	= abx80x_rtc_set_time,
+};
+
+static int abx80x_dt_trickle_cfg(struct device_node *np)
+{
+	const char *diode;
+	int trickle_cfg = 0;
+	int i, ret;
+	u32 tmp;
+
+	ret = of_property_read_string(np, "abracon,tc-diode", &diode);
+	if (ret)
+		return ret;
+
+	if (!strcmp(diode, "standard"))
+		trickle_cfg |= ABX8XX_TRICKLE_STANDARD_DIODE;
+	else if (!strcmp(diode, "schottky"))
+		trickle_cfg |= ABX8XX_TRICKLE_SCHOTTKY_DIODE;
+	else
+		return -EINVAL;
+
+	ret = of_property_read_u32(np, "abracon,tc-resistor", &tmp);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < sizeof(trickle_resistors); i++)
+		if (trickle_resistors[i] == tmp)
+			break;
+
+	if (i == sizeof(trickle_resistors))
+		return -EINVAL;
+
+	return (trickle_cfg | i);
+}
+
+static int abx80x_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct device_node *np = client->dev.of_node;
+	struct rtc_device *rtc;
+	int i, data, err, trickle_cfg = -EINVAL;
+	char buf[7];
+	unsigned int part = id->driver_data;
+	unsigned int partnumber;
+	unsigned int majrev, minrev;
+	unsigned int lot;
+	unsigned int wafer;
+	unsigned int uid;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	err = i2c_smbus_read_i2c_block_data(client, ABX8XX_REG_ID0,
+					    sizeof(buf), buf);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to read partnumber\n");
+		return -EIO;
+	}
+
+	partnumber = (buf[0] << 8) | buf[1];
+	majrev = buf[2] >> 3;
+	minrev = buf[2] & 0x7;
+	lot = ((buf[4] & 0x80) << 2) | ((buf[6] & 0x80) << 1) | buf[3];
+	uid = ((buf[4] & 0x7f) << 8) | buf[5];
+	wafer = (buf[6] & 0x7c) >> 2;
+	dev_info(&client->dev, "model %04x, revision %u.%u, lot %x, wafer %x, uid %x\n",
+		 partnumber, majrev, minrev, lot, wafer, uid);
+
+	data = i2c_smbus_read_byte_data(client, ABX8XX_REG_CTRL1);
+	if (data < 0) {
+		dev_err(&client->dev, "Unable to read control register\n");
+		return -EIO;
+	}
+
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CTRL1,
+					((data & ~ABX8XX_CTRL_12_24) |
+					 ABX8XX_CTRL_WRITE));
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write control register\n");
+		return -EIO;
+	}
+
+	/* part autodetection */
+	if (part == ABX80X) {
+		for (i = 0; abx80x_caps[i].pn; i++)
+			if (partnumber == abx80x_caps[i].pn)
+				break;
+		if (abx80x_caps[i].pn == 0) {
+			dev_err(&client->dev, "Unknown part: %04x\n",
+				partnumber);
+			return -EINVAL;
+		}
+		part = i;
+	}
+
+	if (partnumber != abx80x_caps[part].pn) {
+		dev_err(&client->dev, "partnumber mismatch %04x != %04x\n",
+			partnumber, abx80x_caps[part].pn);
+		return -EINVAL;
+	}
+
+	if (np && abx80x_caps[part].has_tc)
+		trickle_cfg = abx80x_dt_trickle_cfg(np);
+
+	if (trickle_cfg > 0) {
+		dev_info(&client->dev, "Enabling trickle charger: %02x\n",
+			 trickle_cfg);
+		abx80x_enable_trickle_charger(client, trickle_cfg);
+	}
+
+	rtc = devm_rtc_device_register(&client->dev, abx80x_driver.driver.name,
+				       &abx80x_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	i2c_set_clientdata(client, rtc);
+
+	return 0;
+}
+
+static int abx80x_remove(struct i2c_client *client)
+{
+	return 0;
+}
+
+static const struct i2c_device_id abx80x_id[] = {
+	{ "abx80x", ABX80X },
+	{ "ab0801", AB0801 },
+	{ "ab0803", AB0803 },
+	{ "ab0804", AB0804 },
+	{ "ab0805", AB0805 },
+	{ "ab1801", AB1801 },
+	{ "ab1803", AB1803 },
+	{ "ab1804", AB1804 },
+	{ "ab1805", AB1805 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, abx80x_id);
+
+static struct i2c_driver abx80x_driver = {
+	.driver		= {
+		.name	= "rtc-abx80x",
+	},
+	.probe		= abx80x_probe,
+	.remove		= abx80x_remove,
+	.id_table	= abx80x_id,
+};
+
+module_i2c_driver(abx80x_driver);
+
+MODULE_AUTHOR("Philippe De Muyter <phdm@macqel.be>");
+MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
+MODULE_DESCRIPTION("Abracon ABX80X RTC driver");
+MODULE_LICENSE("GPL v2");