rtc: add support for the S-35390A RTC chip

This adds basic get/set time support for the Seiko Instruments S-35390A.
This chip communicates using I2C and is used on the QNAP TS-109/TS-209 NAS
devices.

[[e-mail]: coding-style fixes]
Signed-off-by: Byron Bradley <[e-mail]>
Acked-by: Jean Delvare <[e-mail]>
Acked-by: David Brownell <[e-mail]>
Tested-by: Tim Ellis <[e-mail]>
Cc: Alessandro Zummo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/Kconfig

···
 	  platforms.  The support is integrated with the rest of
 	  the Menelaus driver; it's not separate module.
 
+config RTC_DRV_S35390A
+	tristate "Seiko Instruments S-35390A"
+	help
+	  If you say yes here you will get support for the Seiko
+	  Instruments S-35390A.
+
+	  This driver can also be built as a module. If so the module
+	  will be called rtc-s35390a.
+
 endif # I2C
 
 comment "SPI RTC drivers"

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
+obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
 obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
 obj-$(CONFIG_RTC_DRV_SA1100)	+= rtc-sa1100.o
 obj-$(CONFIG_RTC_DRV_SH)	+= rtc-sh.o

drivers/rtc/rtc-s35390a.c

···
+/*
+ * Seiko Instruments S-35390A RTC Driver
+ *
+ * Copyright (c) 2007 Byron Bradley
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/i2c.h>
+#include <linux/bitrev.h>
+#include <linux/bcd.h>
+#include <linux/slab.h>
+
+#define S35390A_CMD_STATUS1	0
+#define S35390A_CMD_STATUS2	1
+#define S35390A_CMD_TIME1	2
+
+#define S35390A_BYTE_YEAR	0
+#define S35390A_BYTE_MONTH	1
+#define S35390A_BYTE_DAY	2
+#define S35390A_BYTE_WDAY	3
+#define S35390A_BYTE_HOURS	4
+#define S35390A_BYTE_MINS	5
+#define S35390A_BYTE_SECS	6
+
+#define S35390A_FLAG_POC	0x01
+#define S35390A_FLAG_BLD	0x02
+#define S35390A_FLAG_24H	0x40
+#define S35390A_FLAG_RESET	0x80
+#define S35390A_FLAG_TEST	0x01
+
+struct s35390a {
+	struct i2c_client *client[8];
+	struct rtc_device *rtc;
+	int twentyfourhour;
+};
+
+static int s35390a_set_reg(struct s35390a *s35390a, int reg, char *buf, int len)
+{
+	struct i2c_client *client = s35390a->client[reg];
+	struct i2c_msg msg[] = {
+		{ client->addr, 0, len, buf },
+	};
+
+	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
+		return -EIO;
+
+	return 0;
+}
+
+static int s35390a_get_reg(struct s35390a *s35390a, int reg, char *buf, int len)
+{
+	struct i2c_client *client = s35390a->client[reg];
+	struct i2c_msg msg[] = {
+		{ client->addr, I2C_M_RD, len, buf },
+	};
+
+	if ((i2c_transfer(client->adapter, msg, 1)) != 1)
+		return -EIO;
+
+	return 0;
+}
+
+static int s35390a_reset(struct s35390a *s35390a)
+{
+	char buf[1];
+
+	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf)) < 0)
+		return -EIO;
+
+	if (!(buf[0] & (S35390A_FLAG_POC | S35390A_FLAG_BLD)))
+		return 0;
+
+	buf[0] |= (S35390A_FLAG_RESET | S35390A_FLAG_24H);
+	buf[0] &= 0xf0;
+	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf));
+}
+
+static int s35390a_disable_test_mode(struct s35390a *s35390a)
+{
+	char buf[1];
+
+	if (s35390a_get_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf)) < 0)
+		return -EIO;
+
+	if (!(buf[0] & S35390A_FLAG_TEST))
+		return 0;
+
+	buf[0] &= ~S35390A_FLAG_TEST;
+	return s35390a_set_reg(s35390a, S35390A_CMD_STATUS2, buf, sizeof(buf));
+}
+
+static char s35390a_hr2reg(struct s35390a *s35390a, int hour)
+{
+	if (s35390a->twentyfourhour)
+		return BIN2BCD(hour);
+
+	if (hour < 12)
+		return BIN2BCD(hour);
+
+	return 0x40 | BIN2BCD(hour - 12);
+}
+
+static int s35390a_reg2hr(struct s35390a *s35390a, char reg)
+{
+	unsigned hour;
+
+	if (s35390a->twentyfourhour)
+		return BCD2BIN(reg & 0x3f);
+
+	hour = BCD2BIN(reg & 0x3f);
+	if (reg & 0x40)
+		hour += 12;
+
+	return hour;
+}
+
+static int s35390a_set_datetime(struct i2c_client *client, struct rtc_time *tm)
+{
+	struct s35390a	*s35390a = i2c_get_clientdata(client);
+	int i, err;
+	char buf[7];
+
+	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);
+
+	buf[S35390A_BYTE_YEAR] = BIN2BCD(tm->tm_year - 100);
+	buf[S35390A_BYTE_MONTH] = BIN2BCD(tm->tm_mon + 1);
+	buf[S35390A_BYTE_DAY] = BIN2BCD(tm->tm_mday);
+	buf[S35390A_BYTE_WDAY] = BIN2BCD(tm->tm_wday);
+	buf[S35390A_BYTE_HOURS] = s35390a_hr2reg(s35390a, tm->tm_hour);
+	buf[S35390A_BYTE_MINS] = BIN2BCD(tm->tm_min);
+	buf[S35390A_BYTE_SECS] = BIN2BCD(tm->tm_sec);
+
+	/* This chip expects the bits of each byte to be in reverse order */
+	for (i = 0; i < 7; ++i)
+		buf[i] = bitrev8(buf[i]);
+
+	err = s35390a_set_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
+
+	return err;
+}
+
+static int s35390a_get_datetime(struct i2c_client *client, struct rtc_time *tm)
+{
+	struct s35390a *s35390a = i2c_get_clientdata(client);
+	char buf[7];
+	int i, err;
+
+	err = s35390a_get_reg(s35390a, S35390A_CMD_TIME1, buf, sizeof(buf));
+	if (err < 0)
+		return err;
+
+	/* This chip returns the bits of each byte in reverse order */
+	for (i = 0; i < 7; ++i)
+		buf[i] = bitrev8(buf[i]);
+
+	tm->tm_sec = BCD2BIN(buf[S35390A_BYTE_SECS]);
+	tm->tm_min = BCD2BIN(buf[S35390A_BYTE_MINS]);
+	tm->tm_hour = s35390a_reg2hr(s35390a, buf[S35390A_BYTE_HOURS]);
+	tm->tm_wday = BCD2BIN(buf[S35390A_BYTE_WDAY]);
+	tm->tm_mday = BCD2BIN(buf[S35390A_BYTE_DAY]);
+	tm->tm_mon = BCD2BIN(buf[S35390A_BYTE_MONTH]) - 1;
+	tm->tm_year = BCD2BIN(buf[S35390A_BYTE_YEAR]) + 100;
+
+	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);
+
+	return rtc_valid_tm(tm);
+}
+
+static int s35390a_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	return s35390a_get_datetime(to_i2c_client(dev), tm);
+}
+
+static int s35390a_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	return s35390a_set_datetime(to_i2c_client(dev), tm);
+}
+
+static const struct rtc_class_ops s35390a_rtc_ops = {
+	.read_time	= s35390a_rtc_read_time,
+	.set_time	= s35390a_rtc_set_time,
+};
+
+static struct i2c_driver s35390a_driver;
+
+static int s35390a_probe(struct i2c_client *client)
+{
+	int err;
+	unsigned int i;
+	struct s35390a *s35390a;
+	struct rtc_time tm;
+	char buf[1];
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		err = -ENODEV;
+		goto exit;
+	}
+
+	s35390a = kzalloc(sizeof(struct s35390a), GFP_KERNEL);
+	if (!s35390a) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	s35390a->client[0] = client;
+	i2c_set_clientdata(client, s35390a);
+
+	/* This chip uses multiple addresses, use dummy devices for them */
+	for (i = 1; i < 8; ++i) {
+		s35390a->client[i] = i2c_new_dummy(client->adapter,
+					client->addr + i, "rtc-s35390a");
+		if (!s35390a->client[i]) {
+			dev_err(&client->dev, "Address %02x unavailable\n",
+						client->addr + i);
+			err = -EBUSY;
+			goto exit_dummy;
+		}
+	}
+
+	err = s35390a_reset(s35390a);
+	if (err < 0) {
+		dev_err(&client->dev, "error resetting chip\n");
+		goto exit_dummy;
+	}
+
+	err = s35390a_disable_test_mode(s35390a);
+	if (err < 0) {
+		dev_err(&client->dev, "error disabling test mode\n");
+		goto exit_dummy;
+	}
+
+	err = s35390a_get_reg(s35390a, S35390A_CMD_STATUS1, buf, sizeof(buf));
+	if (err < 0) {
+		dev_err(&client->dev, "error checking 12/24 hour mode\n");
+		goto exit_dummy;
+	}
+	if (buf[0] & S35390A_FLAG_24H)
+		s35390a->twentyfourhour = 1;
+	else
+		s35390a->twentyfourhour = 0;
+
+	if (s35390a_get_datetime(client, &tm) < 0)
+		dev_warn(&client->dev, "clock needs to be set\n");
+
+	s35390a->rtc = rtc_device_register(s35390a_driver.driver.name,
+				&client->dev, &s35390a_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(s35390a->rtc)) {
+		err = PTR_ERR(s35390a->rtc);
+		goto exit_dummy;
+	}
+	return 0;
+
+exit_dummy:
+	for (i = 1; i < 8; ++i)
+		if (s35390a->client[i])
+			i2c_unregister_device(s35390a->client[i]);
+	kfree(s35390a);
+	i2c_set_clientdata(client, NULL);
+
+exit:
+	return err;
+}
+
+static int s35390a_remove(struct i2c_client *client)
+{
+	unsigned int i;
+
+	struct s35390a *s35390a = i2c_get_clientdata(client);
+	for (i = 1; i < 8; ++i)
+		if (s35390a->client[i])
+			i2c_unregister_device(s35390a->client[i]);
+
+	rtc_device_unregister(s35390a->rtc);
+	kfree(s35390a);
+	i2c_set_clientdata(client, NULL);
+
+	return 0;
+}
+
+static struct i2c_driver s35390a_driver = {
+	.driver		= {
+		.name	= "rtc-s35390a",
+	},
+	.probe		= s35390a_probe,
+	.remove		= s35390a_remove,
+};
+
+static int __init s35390a_rtc_init(void)
+{
+	return i2c_add_driver(&s35390a_driver);
+}
+
+static void __exit s35390a_rtc_exit(void)
+{
+	i2c_del_driver(&s35390a_driver);
+}
+
+MODULE_AUTHOR("Byron Bradley <[e-mail]>");
+MODULE_DESCRIPTION("S35390A RTC driver");
+MODULE_LICENSE("GPL");
+
+module_init(s35390a_rtc_init);
+module_exit(s35390a_rtc_exit);