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rtc: add support for DS3232 RTC
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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>
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Roy Zang authored and Linus Torvalds committed Aug 11, 2010
1 parent 2f11e57 commit c03675f
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10 changes: 10 additions & 0 deletions drivers/rtc/Kconfig
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Expand Up @@ -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
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1 change: 1 addition & 0 deletions drivers/rtc/Makefile
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Expand Up @@ -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
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326 changes: 326 additions & 0 deletions drivers/rtc/rtc-ds3232.c
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@@ -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");

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