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linux/drivers/rtc/rtc-ds1374.c
Roel Kluin fa7af8b1bb rtc: test before subtraction on unsigned 
new_alarm is unsigned so test before the subtraction.

[akpm@linux-foundation.org: time-wrapping fix]
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: David Brownell <david-b@pacbell.net>
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>
2009-04-01 08:59:26 -07:00

479 lines
11 KiB
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/*
* RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
*
* Based on code by Randy Vinson <rvinson@mvista.com>,
* which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
*
* Copyright (C) 2006-2007 Freescale Semiconductor
*
* 2005 (c) MontaVista Software, Inc. This file is licensed under
* the terms of the GNU General Public License version 2. This program
* is licensed "as is" without any warranty of any kind, whether express
* or implied.
*/
/*
* 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>
#define DS1374_REG_TOD0 0x00 /* Time of Day */
#define DS1374_REG_TOD1 0x01
#define DS1374_REG_TOD2 0x02
#define DS1374_REG_TOD3 0x03
#define DS1374_REG_WDALM0 0x04 /* Watchdog/Alarm */
#define DS1374_REG_WDALM1 0x05
#define DS1374_REG_WDALM2 0x06
#define DS1374_REG_CR 0x07 /* Control */
#define DS1374_REG_CR_AIE 0x01 /* Alarm Int. Enable */
#define DS1374_REG_CR_WDALM 0x20 /* 1=Watchdog, 0=Alarm */
#define DS1374_REG_CR_WACE 0x40 /* WD/Alarm counter enable */
#define DS1374_REG_SR 0x08 /* Status */
#define DS1374_REG_SR_OSF 0x80 /* Oscillator Stop Flag */
#define DS1374_REG_SR_AF 0x01 /* Alarm Flag */
#define DS1374_REG_TCR 0x09 /* Trickle Charge */
static const struct i2c_device_id ds1374_id[] = {
{ "ds1374", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, ds1374_id);
struct ds1374 {
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 ds1374_driver;
static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
int reg, int nbytes)
{
u8 buf[4];
int ret;
int i;
if (nbytes > 4) {
WARN_ON(1);
return -EINVAL;
}
ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
if (ret < 0)
return ret;
if (ret < nbytes)
return -EIO;
for (i = nbytes - 1, *time = 0; i >= 0; i--)
*time = (*time << 8) | buf[i];
return 0;
}
static int ds1374_write_rtc(struct i2c_client *client, u32 time,
int reg, int nbytes)
{
u8 buf[4];
int i;
if (nbytes > 4) {
WARN_ON(1);
return -EINVAL;
}
for (i = 0; i < nbytes; i++) {
buf[i] = time & 0xff;
time >>= 8;
}
return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
}
static int ds1374_check_rtc_status(struct i2c_client *client)
{
int ret = 0;
int control, stat;
stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
if (stat < 0)
return stat;
if (stat & DS1374_REG_SR_OSF)
dev_warn(&client->dev,
"oscillator discontinuity flagged, "
"time unreliable\n");
stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
ret = i2c_smbus_write_byte_data(client, DS1374_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, DS1374_REG_CR);
if (control < 0)
return control;
control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
}
static int ds1374_read_time(struct device *dev, struct rtc_time *time)
{
struct i2c_client *client = to_i2c_client(dev);
u32 itime;
int ret;
ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
if (!ret)
rtc_time_to_tm(itime, time);
return ret;
}
static int ds1374_set_time(struct device *dev, struct rtc_time *time)
{
struct i2c_client *client = to_i2c_client(dev);
unsigned long itime;
rtc_tm_to_time(time, &itime);
return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
}
/* The ds1374 has a decrementer for an alarm, rather than a comparator.
* If the time of day is changed, then the alarm will need to be
* reset.
*/
static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
struct i2c_client *client = to_i2c_client(dev);
struct ds1374 *ds1374 = i2c_get_clientdata(client);
u32 now, cur_alarm;
int cr, sr;
int ret = 0;
if (client->irq <= 0)
return -EINVAL;
mutex_lock(&ds1374->mutex);
cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
if (ret < 0)
goto out;
sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
if (ret < 0)
goto out;
ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
if (ret)
goto out;
ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
if (ret)
goto out;
rtc_time_to_tm(now + cur_alarm, &alarm->time);
alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
alarm->pending = !!(sr & DS1374_REG_SR_AF);
out:
mutex_unlock(&ds1374->mutex);
return ret;
}
static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
{
struct i2c_client *client = to_i2c_client(dev);
struct ds1374 *ds1374 = i2c_get_clientdata(client);
struct rtc_time now;
unsigned long new_alarm, itime;
int cr;
int ret = 0;
if (client->irq <= 0)
return -EINVAL;
ret = ds1374_read_time(dev, &now);
if (ret < 0)
return ret;
rtc_tm_to_time(&alarm->time, &new_alarm);
rtc_tm_to_time(&now, &itime);
/* This can happen due to races, in addition to dates that are
* truly in the past. To avoid requiring the caller to check for
* races, dates in the past are assumed to be in the recent past
* (i.e. not something that we'd rather the caller know about via
* an error), and the alarm is set to go off as soon as possible.
*/
if (time_before_eq(new_alarm, itime))
new_alarm = 1;
else
new_alarm -= itime;
mutex_lock(&ds1374->mutex);
ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
if (ret < 0)
goto out;
/* Disable any existing alarm before setting the new one
* (or lack thereof). */
cr &= ~DS1374_REG_CR_WACE;
ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
if (ret < 0)
goto out;
ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
if (ret)
goto out;
if (alarm->enabled) {
cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
cr &= ~DS1374_REG_CR_WDALM;
ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
}
out:
mutex_unlock(&ds1374->mutex);
return ret;
}
static irqreturn_t ds1374_irq(int irq, void *dev_id)
{
struct i2c_client *client = dev_id;
struct ds1374 *ds1374 = i2c_get_clientdata(client);
disable_irq_nosync(irq);
schedule_work(&ds1374->work);
return IRQ_HANDLED;
}
static void ds1374_work(struct work_struct *work)
{
struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
struct i2c_client *client = ds1374->client;
int stat, control;
mutex_lock(&ds1374->mutex);
stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
if (stat < 0)
return;
if (stat & DS1374_REG_SR_AF) {
stat &= ~DS1374_REG_SR_AF;
i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
if (control < 0)
goto out;
control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
/* rtc_update_irq() assumes that it is called
* from IRQ-disabled context.
*/
local_irq_disable();
rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
local_irq_enable();
}
out:
if (!ds1374->exiting)
enable_irq(client->irq);
mutex_unlock(&ds1374->mutex);
}
static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
struct ds1374 *ds1374 = i2c_get_clientdata(client);
int ret = -ENOIOCTLCMD;
mutex_lock(&ds1374->mutex);
switch (cmd) {
case RTC_AIE_OFF:
ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
if (ret < 0)
goto out;
ret &= ~DS1374_REG_CR_WACE;
ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
if (ret < 0)
goto out;
break;
case RTC_AIE_ON:
ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
if (ret < 0)
goto out;
ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
ret &= ~DS1374_REG_CR_WDALM;
ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
if (ret < 0)
goto out;
break;
}
out:
mutex_unlock(&ds1374->mutex);
return ret;
}
static const struct rtc_class_ops ds1374_rtc_ops = {
.read_time = ds1374_read_time,
.set_time = ds1374_set_time,
.read_alarm = ds1374_read_alarm,
.set_alarm = ds1374_set_alarm,
.ioctl = ds1374_ioctl,
};
static int ds1374_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct ds1374 *ds1374;
int ret;
ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
if (!ds1374)
return -ENOMEM;
ds1374->client = client;
i2c_set_clientdata(client, ds1374);
INIT_WORK(&ds1374->work, ds1374_work);
mutex_init(&ds1374->mutex);
ret = ds1374_check_rtc_status(client);
if (ret)
goto out_free;
if (client->irq > 0) {
ret = request_irq(client->irq, ds1374_irq, 0,
"ds1374", client);
if (ret) {
dev_err(&client->dev, "unable to request IRQ\n");
goto out_free;
}
}
ds1374->rtc = rtc_device_register(client->name, &client->dev,
&ds1374_rtc_ops, THIS_MODULE);
if (IS_ERR(ds1374->rtc)) {
ret = PTR_ERR(ds1374->rtc);
dev_err(&client->dev, "unable to register the class device\n");
goto out_irq;
}
return 0;
out_irq:
if (client->irq > 0)
free_irq(client->irq, client);
out_free:
i2c_set_clientdata(client, NULL);
kfree(ds1374);
return ret;
}
static int __devexit ds1374_remove(struct i2c_client *client)
{
struct ds1374 *ds1374 = i2c_get_clientdata(client);
if (client->irq > 0) {
mutex_lock(&ds1374->mutex);
ds1374->exiting = 1;
mutex_unlock(&ds1374->mutex);
free_irq(client->irq, client);
flush_scheduled_work();
}
rtc_device_unregister(ds1374->rtc);
i2c_set_clientdata(client, NULL);
kfree(ds1374);
return 0;
}
#ifdef CONFIG_PM
static int ds1374_suspend(struct i2c_client *client, pm_message_t state)
{
if (client->irq >= 0 && device_may_wakeup(&client->dev))
enable_irq_wake(client->irq);
return 0;
}
static int ds1374_resume(struct i2c_client *client)
{
if (client->irq >= 0 && device_may_wakeup(&client->dev))
disable_irq_wake(client->irq);
return 0;
}
#else
#define ds1374_suspend NULL
#define ds1374_resume NULL
#endif
static struct i2c_driver ds1374_driver = {
.driver = {
.name = "rtc-ds1374",
.owner = THIS_MODULE,
},
.probe = ds1374_probe,
.suspend = ds1374_suspend,
.resume = ds1374_resume,
.remove = __devexit_p(ds1374_remove),
.id_table = ds1374_id,
};
static int __init ds1374_init(void)
{
return i2c_add_driver(&ds1374_driver);
}
static void __exit ds1374_exit(void)
{
i2c_del_driver(&ds1374_driver);
}
module_init(ds1374_init);
module_exit(ds1374_exit);
MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
MODULE_LICENSE("GPL");
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