rtc: add driver for BQ32000 I2C RTC

This patch adds basic support for Texas Instruments BQ32000 I2C RTC.  Only
time reading/writing is implemented.  Advanced features, such as trickle
charger and crystal calibration are not supported.

Signed-off-by: Piotr Ziecik <kosmo@semihalf.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 214 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 9930d79fa51f..40c168bf6984 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -242,6 +242,15 @@ config RTC_DRV_M41T80_WDT
           If you say Y here you will get support for the
           watchdog timer in the ST M41T60 and M41T80 RTC chips series.
 
+config RTC_DRV_BQ32K
+        tristate "TI BQ32000"
+        help
+          If you say Y here you will get support for the TI
+          BQ32000 I2C RTC chip.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-bq32k.
+
 config RTC_DRV_DM355EVM
         tristate "TI DaVinci DM355 EVM RTC"
         depends on MFD_DM355EVM_MSP
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 6fa20f4ac3f1..52f5f3c3b8e0 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o
 obj-$(CONFIG_RTC_DRV_AT91SAM9)  += rtc-at91sam9.o
 obj-$(CONFIG_RTC_DRV_AU1XXX)    += rtc-au1xxx.o
 obj-$(CONFIG_RTC_DRV_BFIN)      += rtc-bfin.o
+obj-$(CONFIG_RTC_DRV_BQ32K)     += rtc-bq32k.o
 obj-$(CONFIG_RTC_DRV_BQ4802)    += rtc-bq4802.o
 obj-$(CONFIG_RTC_DRV_CMOS)      += rtc-cmos.o
 obj-$(CONFIG_RTC_DRV_COH901331) += rtc-coh901331.o
diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c
new file mode 100644
index 000000000000..408cc8f735be
--- /dev/null
+++ b/drivers/rtc/rtc-bq32k.c
@@ -0,0 +1,204 @@
+/*
+ * Driver for TI BQ32000 RTC.
+ *
+ * Copyright (C) 2009 Semihalf.
+ *
+ * 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/module.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/bcd.h>
+
+#define BQ32K_SECONDS           0x00    /* Seconds register address */
+#define BQ32K_SECONDS_MASK      0x7F    /* Mask over seconds value */
+#define BQ32K_STOP              0x80    /* Oscillator Stop flat */
+
+#define BQ32K_MINUTES           0x01    /* Minutes register address */
+#define BQ32K_MINUTES_MASK      0x7F    /* Mask over minutes value */
+#define BQ32K_OF                0x80    /* Oscillator Failure flag */
+
+#define BQ32K_HOURS_MASK        0x3F    /* Mask over hours value */
+#define BQ32K_CENT              0x40    /* Century flag */
+#define BQ32K_CENT_EN           0x80    /* Century flag enable bit */
+
+struct bq32k_regs {
+        uint8_t         seconds;
+        uint8_t         minutes;
+        uint8_t         cent_hours;
+        uint8_t         day;
+        uint8_t         date;
+        uint8_t         month;
+        uint8_t         years;
+};
+
+static struct i2c_driver bq32k_driver;
+
+static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        struct i2c_msg msgs[] = {
+                {
+                        .addr = client->addr,
+                        .flags = 0,
+                        .len = 1,
+                        .buf = &off,
+                }, {
+                        .addr = client->addr,
+                        .flags = I2C_M_RD,
+                        .len = len,
+                        .buf = data,
+                }
+        };
+
+        if (i2c_transfer(client->adapter, msgs, 2) == 2)
+                return 0;
+
+        return -EIO;
+}
+
+static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        uint8_t buffer[len + 1];
+
+        buffer[0] = off;
+        memcpy(&buffer[1], data, len);
+
+        if (i2c_master_send(client, buffer, len + 1) == len + 1)
+                return 0;
+
+        return -EIO;
+}
+
+static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct bq32k_regs regs;
+        int error;
+
+        error = bq32k_read(dev, &regs, 0, sizeof(regs));
+        if (error)
+                return error;
+
+        tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
+        tm->tm_min = bcd2bin(regs.minutes & BQ32K_SECONDS_MASK);
+        tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
+        tm->tm_mday = bcd2bin(regs.date);
+        tm->tm_wday = bcd2bin(regs.day) - 1;
+        tm->tm_mon = bcd2bin(regs.month) - 1;
+        tm->tm_year = bcd2bin(regs.years) +
+                                ((regs.cent_hours & BQ32K_CENT) ? 100 : 0);
+
+        return rtc_valid_tm(tm);
+}
+
+static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+        struct bq32k_regs regs;
+
+        regs.seconds = bin2bcd(tm->tm_sec);
+        regs.minutes = bin2bcd(tm->tm_min);
+        regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
+        regs.day = bin2bcd(tm->tm_wday + 1);
+        regs.date = bin2bcd(tm->tm_mday);
+        regs.month = bin2bcd(tm->tm_mon + 1);
+
+        if (tm->tm_year >= 100) {
+                regs.cent_hours |= BQ32K_CENT;
+                regs.years = bin2bcd(tm->tm_year - 100);
+        } else
+                regs.years = bin2bcd(tm->tm_year);
+
+        return bq32k_write(dev, &regs, 0, sizeof(regs));
+}
+
+static const struct rtc_class_ops bq32k_rtc_ops = {
+        .read_time      = bq32k_rtc_read_time,
+        .set_time       = bq32k_rtc_set_time,
+};
+
+static int bq32k_probe(struct i2c_client *client,
+                                const struct i2c_device_id *id)
+{
+        struct device *dev = &client->dev;
+        struct rtc_device *rtc;
+        uint8_t reg;
+        int error;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+                return -ENODEV;
+
+        /* Check Oscillator Stop flag */
+        error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
+        if (!error && (reg & BQ32K_STOP)) {
+                dev_warn(dev, "Oscillator was halted. Restarting...\n");
+                reg &= ~BQ32K_STOP;
+                error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
+        }
+        if (error)
+                return error;
+
+        /* Check Oscillator Failure flag */
+        error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
+        if (!error && (reg & BQ32K_OF)) {
+                dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
+                reg &= ~BQ32K_OF;
+                error = bq32k_write(dev, &reg, BQ32K_MINUTES, 1);
+        }
+        if (error)
+                return error;
+
+        rtc = rtc_device_register(bq32k_driver.driver.name, &client->dev,
+                                                &bq32k_rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc))
+                return PTR_ERR(rtc);
+
+        i2c_set_clientdata(client, rtc);
+
+        return 0;
+}
+
+static int __devexit bq32k_remove(struct i2c_client *client)
+{
+        struct rtc_device *rtc = i2c_get_clientdata(client);
+
+        rtc_device_unregister(rtc);
+        return 0;
+}
+
+static const struct i2c_device_id bq32k_id[] = {
+        { "bq32000", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, bq32k_id);
+
+static struct i2c_driver bq32k_driver = {
+        .driver = {
+                .name   = "bq32k",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = bq32k_probe,
+        .remove         = __devexit_p(bq32k_remove),
+        .id_table       = bq32k_id,
+};
+
+static __init int bq32k_init(void)
+{
+        return i2c_add_driver(&bq32k_driver);
+}
+module_init(bq32k_init);
+
+static __exit void bq32k_exit(void)
+{
+        i2c_del_driver(&bq32k_driver);
+}
+module_exit(bq32k_exit);
+
+MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
+MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
+MODULE_LICENSE("GPL");