rtc: add support for DS3232 RTC

Add a driver for the DS3232 RTC chip via the I2C bus.  Alarms are not
supported in this version of the driver.

[akpm@linux-foundation.org: fix Kconfig help text]
Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Jingchang Lu <b22599@freescale.com>
Signed-off-by: Srikanth Srinivasan <srikanth.srinivasan@freescale.com>
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Cc: Kumar Gala <kumar.gala@freescale.com>
Cc: 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, 337 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 999db51e6a5..06cb8d6823a 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -166,6 +166,16 @@ config RTC_DRV_DS1672
           This driver can also be built as a module. If so, the module
           will be called rtc-ds1672.
 
+config RTC_DRV_DS3232
+        tristate "Dallas/Maxim DS3232"
+        depends on RTC_CLASS && I2C
+        help
+          If you say yes here you get support for Dallas Semiconductor
+          DS3232 real-time clock chips.
+
+          This driver can also be built as a module.  If so, the module
+          will be called rtc-ds3232.
+
 config RTC_DRV_MAX6900
         tristate "Maxim MAX6900"
         help
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index e29b7f9377d..0f207b3b583 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_RTC_DRV_DS1511)	+= rtc-ds1511.o
 obj-$(CONFIG_RTC_DRV_DS1553)    += rtc-ds1553.o
 obj-$(CONFIG_RTC_DRV_DS1672)    += rtc-ds1672.o
 obj-$(CONFIG_RTC_DRV_DS1742)    += rtc-ds1742.o
+obj-$(CONFIG_RTC_DRV_DS3232)    += rtc-ds3232.o
 obj-$(CONFIG_RTC_DRV_DS3234)    += rtc-ds3234.o
 obj-$(CONFIG_RTC_DRV_EFI)       += rtc-efi.o
 obj-$(CONFIG_RTC_DRV_EP93XX)    += rtc-ep93xx.o
diff --git a/drivers/rtc/rtc-ds3232.c b/drivers/rtc/rtc-ds3232.c
new file mode 100644
index 00000000000..9daed8db83d
--- /dev/null
+++ b/drivers/rtc/rtc-ds3232.c
@@ -0,0 +1,326 @@
+/*
+ * RTC client/driver for the Maxim/Dallas DS3232 Real-Time Clock over I2C
+ *
+ * Copyright (C) 2009-2010 Freescale Semiconductor.
+ *
+ * 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.
+ */
+/*
+ * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
+ * recommened in .../Documentation/i2c/writing-clients section
+ * "Sending and receiving", using SMBus level communication is preferred.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+
+#define DS3232_REG_SECONDS      0x00
+#define DS3232_REG_MINUTES      0x01
+#define DS3232_REG_HOURS        0x02
+#define DS3232_REG_AMPM         0x02
+#define DS3232_REG_DAY          0x03
+#define DS3232_REG_DATE         0x04
+#define DS3232_REG_MONTH        0x05
+#define DS3232_REG_CENTURY      0x05
+#define DS3232_REG_YEAR         0x06
+#define DS3232_REG_ALARM1         0x07  /* Alarm 1 BASE */
+#define DS3232_REG_ALARM2         0x0B  /* Alarm 2 BASE */
+#define DS3232_REG_CR           0x0E    /* Control register */
+#       define DS3232_REG_CR_nEOSC        0x80
+#       define DS3232_REG_CR_INTCN        0x04
+#       define DS3232_REG_CR_A2IE        0x02
+#       define DS3232_REG_CR_A1IE        0x01
+
+#define DS3232_REG_SR   0x0F    /* control/status register */
+#       define DS3232_REG_SR_OSF   0x80
+#       define DS3232_REG_SR_BSY   0x04
+#       define DS3232_REG_SR_A2F   0x02
+#       define DS3232_REG_SR_A1F   0x01
+
+struct ds3232 {
+        struct i2c_client *client;
+        struct rtc_device *rtc;
+        struct work_struct work;
+
+        /* The mutex protects alarm operations, and prevents a race
+         * between the enable_irq() in the workqueue and the free_irq()
+         * in the remove function.
+         */
+        struct mutex mutex;
+        int exiting;
+};
+
+static struct i2c_driver ds3232_driver;
+
+static int ds3232_check_rtc_status(struct i2c_client *client)
+{
+        int ret = 0;
+        int control, stat;
+
+        stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
+        if (stat < 0)
+                return stat;
+
+        if (stat & DS3232_REG_SR_OSF)
+                dev_warn(&client->dev,
+                                "oscillator discontinuity flagged, "
+                                "time unreliable\n");
+
+        stat &= ~(DS3232_REG_SR_OSF | DS3232_REG_SR_A1F | DS3232_REG_SR_A2F);
+
+        ret = i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
+        if (ret < 0)
+                return ret;
+
+        /* If the alarm is pending, clear it before requesting
+         * the interrupt, so an interrupt event isn't reported
+         * before everything is initialized.
+         */
+
+        control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
+        if (control < 0)
+                return control;
+
+        control &= ~(DS3232_REG_CR_A1IE | DS3232_REG_CR_A2IE);
+        control |= DS3232_REG_CR_INTCN;
+
+        return i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
+}
+
+static int ds3232_read_time(struct device *dev, struct rtc_time *time)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        int ret;
+        u8 buf[7];
+        unsigned int year, month, day, hour, minute, second;
+        unsigned int week, twelve_hr, am_pm;
+        unsigned int century, add_century = 0;
+
+        ret = i2c_smbus_read_i2c_block_data(client, DS3232_REG_SECONDS, 7, buf);
+
+        if (ret < 0)
+                return ret;
+        if (ret < 7)
+                return -EIO;
+
+        second = buf[0];
+        minute = buf[1];
+        hour = buf[2];
+        week = buf[3];
+        day = buf[4];
+        month = buf[5];
+        year = buf[6];
+
+        /* Extract additional information for AM/PM and century */
+
+        twelve_hr = hour & 0x40;
+        am_pm = hour & 0x20;
+        century = month & 0x80;
+
+        /* Write to rtc_time structure */
+
+        time->tm_sec = bcd2bin(second);
+        time->tm_min = bcd2bin(minute);
+        if (twelve_hr) {
+                /* Convert to 24 hr */
+                if (am_pm)
+                        time->tm_hour = bcd2bin(hour & 0x1F) + 12;
+                else
+                        time->tm_hour = bcd2bin(hour & 0x1F);
+        } else {
+                time->tm_hour = bcd2bin(hour);
+        }
+
+        time->tm_wday = bcd2bin(week);
+        time->tm_mday = bcd2bin(day);
+        time->tm_mon = bcd2bin(month & 0x7F);
+        if (century)
+                add_century = 100;
+
+        time->tm_year = bcd2bin(year) + add_century;
+
+        return rtc_valid_tm(time);
+}
+
+static int ds3232_set_time(struct device *dev, struct rtc_time *time)
+{
+        struct i2c_client *client = to_i2c_client(dev);
+        u8 buf[7];
+
+        /* Extract time from rtc_time and load into ds3232*/
+
+        buf[0] = bin2bcd(time->tm_sec);
+        buf[1] = bin2bcd(time->tm_min);
+        buf[2] = bin2bcd(time->tm_hour);
+        buf[3] = bin2bcd(time->tm_wday); /* Day of the week */
+        buf[4] = bin2bcd(time->tm_mday); /* Date */
+        buf[5] = bin2bcd(time->tm_mon);
+        if (time->tm_year >= 100) {
+                buf[5] |= 0x80;
+                buf[6] = bin2bcd(time->tm_year - 100);
+        } else {
+                buf[6] = bin2bcd(time->tm_year);
+        }
+
+        return i2c_smbus_write_i2c_block_data(client,
+                                              DS3232_REG_SECONDS, 7, buf);
+}
+
+static irqreturn_t ds3232_irq(int irq, void *dev_id)
+{
+        struct i2c_client *client = dev_id;
+        struct ds3232 *ds3232 = i2c_get_clientdata(client);
+
+        disable_irq_nosync(irq);
+        schedule_work(&ds3232->work);
+        return IRQ_HANDLED;
+}
+
+static void ds3232_work(struct work_struct *work)
+{
+        struct ds3232 *ds3232 = container_of(work, struct ds3232, work);
+        struct i2c_client *client = ds3232->client;
+        int stat, control;
+
+        mutex_lock(&ds3232->mutex);
+
+        stat = i2c_smbus_read_byte_data(client, DS3232_REG_SR);
+        if (stat < 0)
+                goto unlock;
+
+        if (stat & DS3232_REG_SR_A1F) {
+                control = i2c_smbus_read_byte_data(client, DS3232_REG_CR);
+                if (control < 0)
+                        goto out;
+                /* disable alarm1 interrupt */
+                control &= ~(DS3232_REG_CR_A1IE);
+                i2c_smbus_write_byte_data(client, DS3232_REG_CR, control);
+
+                /* clear the alarm pend flag */
+                stat &= ~DS3232_REG_SR_A1F;
+                i2c_smbus_write_byte_data(client, DS3232_REG_SR, stat);
+
+                rtc_update_irq(ds3232->rtc, 1, RTC_AF | RTC_IRQF);
+        }
+
+out:
+        if (!ds3232->exiting)
+                enable_irq(client->irq);
+unlock:
+        mutex_unlock(&ds3232->mutex);
+}
+
+static const struct rtc_class_ops ds3232_rtc_ops = {
+        .read_time = ds3232_read_time,
+        .set_time = ds3232_set_time,
+};
+
+static int __devinit ds3232_probe(struct i2c_client *client,
+                const struct i2c_device_id *id)
+{
+        struct ds3232 *ds3232;
+        int ret;
+
+        ds3232 = kzalloc(sizeof(struct ds3232), GFP_KERNEL);
+        if (!ds3232)
+                return -ENOMEM;
+
+        ds3232->client = client;
+        i2c_set_clientdata(client, ds3232);
+
+        INIT_WORK(&ds3232->work, ds3232_work);
+        mutex_init(&ds3232->mutex);
+
+        ret = ds3232_check_rtc_status(client);
+        if (ret)
+                goto out_free;
+
+        ds3232->rtc = rtc_device_register(client->name, &client->dev,
+                                          &ds3232_rtc_ops, THIS_MODULE);
+        if (IS_ERR(ds3232->rtc)) {
+                ret = PTR_ERR(ds3232->rtc);
+                dev_err(&client->dev, "unable to register the class device\n");
+                goto out_irq;
+        }
+
+        if (client->irq >= 0) {
+                ret = request_irq(client->irq, ds3232_irq, 0,
+                                 "ds3232", client);
+                if (ret) {
+                        dev_err(&client->dev, "unable to request IRQ\n");
+                        goto out_free;
+                }
+        }
+
+        return 0;
+
+out_irq:
+        if (client->irq >= 0)
+                free_irq(client->irq, client);
+
+out_free:
+        i2c_set_clientdata(client, NULL);
+        kfree(ds3232);
+        return ret;
+}
+
+static int __devexit ds3232_remove(struct i2c_client *client)
+{
+        struct ds3232 *ds3232 = i2c_get_clientdata(client);
+
+        if (client->irq >= 0) {
+                mutex_lock(&ds3232->mutex);
+                ds3232->exiting = 1;
+                mutex_unlock(&ds3232->mutex);
+
+                free_irq(client->irq, client);
+                flush_scheduled_work();
+        }
+
+        rtc_device_unregister(ds3232->rtc);
+        i2c_set_clientdata(client, NULL);
+        kfree(ds3232);
+        return 0;
+}
+
+static const struct i2c_device_id ds3232_id[] = {
+        { "ds3232", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, ds3232_id);
+
+static struct i2c_driver ds3232_driver = {
+        .driver = {
+                .name = "rtc-ds3232",
+                .owner = THIS_MODULE,
+        },
+        .probe = ds3232_probe,
+        .remove = __devexit_p(ds3232_remove),
+        .id_table = ds3232_id,
+};
+
+static int __init ds3232_init(void)
+{
+        return i2c_add_driver(&ds3232_driver);
+}
+
+static void __exit ds3232_exit(void)
+{
+        i2c_del_driver(&ds3232_driver);
+}
+
+module_init(ds3232_init);
+module_exit(ds3232_exit);
+
+MODULE_AUTHOR("Srikanth Srinivasan <srikanth.srinivasan@freescale.com>");
+MODULE_DESCRIPTION("Maxim/Dallas DS3232 RTC Driver");
+MODULE_LICENSE("GPL");