/*
* drivers/i2c/chips/ds1374.c
*
* I2C client/driver for the Maxim/Dallas DS1374 Real-Time Clock
*
* Author: Randy Vinson <rvinson@mvista.com>
*
* Based on the m41t00.c by Mark Greer <mgreer@mvista.com>
*
* 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.
*/
/*
* This i2c client/driver wedges between the drivers/char/genrtc.c RTC
* interface and the SMBus interface of the i2c subsystem.
* 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/mutex.h>
#define DS1374_REG_TOD0 0x00
#define DS1374_REG_TOD1 0x01
#define DS1374_REG_TOD2 0x02
#define DS1374_REG_TOD3 0x03
#define DS1374_REG_WDALM0 0x04
#define DS1374_REG_WDALM1 0x05
#define DS1374_REG_WDALM2 0x06
#define DS1374_REG_CR 0x07
#define DS1374_REG_SR 0x08
#define DS1374_REG_SR_OSF 0x80
#define DS1374_REG_TCR 0x09
#define DS1374_DRV_NAME "ds1374"
static DEFINE_MUTEX(ds1374_mutex);
static struct i2c_driver ds1374_driver;
static struct i2c_client *save_client;
static unsigned short ignore[] = { I2C_CLIENT_END };
static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
static struct i2c_client_address_data addr_data = {
.normal_i2c = normal_addr,
.probe = ignore,
.ignore = ignore,
};
static ulong ds1374_read_rtc(void)
{
ulong time = 0;
int reg = DS1374_REG_WDALM0;
while (reg--) {
s32 tmp;
if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
dev_warn(&save_client->dev,
"can't read from rtc chip\n");
return 0;
}
time = (time << 8) | (tmp & 0xff);
}
return time;
}
static void ds1374_write_rtc(ulong time)
{
int reg;
for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
< 0) {
dev_warn(&save_client->dev,
"can't write to rtc chip\n");
break;
}
time = time >> 8;
}
}
static void ds1374_check_rtc_status(void)
{
s32 tmp;
tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
if (tmp < 0) {
dev_warn(&save_client->dev,
"can't read status from rtc chip\n");
return;
}
if (tmp & DS1374_REG_SR_OSF) {
dev_warn(&save_client->dev,
"oscillator discontinuity flagged, time unreliable\n");
tmp &= ~DS1374_REG_SR_OSF;
tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
tmp & 0xff);
if (tmp < 0)
dev_warn(&save_client->dev,
"can't clear discontinuity notification\n");
}
}
ulong ds1374_get_rtc_time(void)
{
ulong t1, t2;
int limit = 10; /* arbitrary retry limit */
mutex_lock(&ds1374_mutex);
/*
* Since the reads are being performed one byte at a time using
* the SMBus vs a 4-byte i2c transfer, there is a chance that a
* carry will occur during the read. To detect this, 2 reads are
* performed and compared.
*/
do {
t1 = ds1374_read_rtc();
t2 = ds1374_read_rtc();
} while (t1 != t2 && limit--);
mutex_unlock(&ds1374_mutex);
if (t1 != t2) {
dev_warn(&save_client->dev,
"can't get consistent time from rtc chip\n");
t1 = 0;
}
return t1;
}
static void ds1374_set_tlet(ulong arg)
{
ulong t1, t2;
int limit = 10; /* arbitrary retry limit */
t1 = *(ulong *) arg;
mutex_lock(&ds1374_mutex);
/*
* Since the writes are being performed one byte at a time using
* the SMBus vs a 4-byte i2c transfer, there is a chance that a
* carry will occur during the write. To detect this, the write
* value is read back and compared.
*/
do {
ds1374_write_rtc(t1);
t2 = ds1374_read_rtc();
} while (t1 != t2 && limit--);
mutex_unlock(&ds1374_mutex);
if (t1 != t2)
dev_warn(&save_client->dev,
"can't confirm time set from rtc chip\n");
}
static ulong new_time;
static DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet,
(ulong) & new_time);
int ds1374_set_rtc_time(ulong nowtime)
{
new_time = nowtime;
if (in_interrupt())
tasklet_schedule(&ds1374_tasklet);
else
ds1374_set_tlet((ulong) & new_time);
return 0;
}
/*
*****************************************************************************
*
* Driver Interface
*
*****************************************************************************
*/
static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
{
struct i2c_client *client;
int rc;
client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
if (!client)
return -ENOMEM;
strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
client->addr = addr;
client->adapter = adap;
client->driver = &ds1374_driver;
if ((rc = i2c_attach_client(client)) != 0) {
kfree(client);
return rc;
}
save_client = client;
ds1374_check_rtc_status();
return 0;
}
static int ds1374_attach(struct i2c_adapter *adap)
{
return i2c_probe(adap, &addr_data, ds1374_probe);
}
static int ds1374_detach(struct i2c_client *client)
{
int rc;
if ((rc = i2c_detach_client(client)) == 0) {
kfree(i2c_get_clientdata(client));
tasklet_kill(&ds1374_tasklet);
}
return rc;
}
static struct i2c_driver ds1374_driver = {
.driver = {
.name = DS1374_DRV_NAME,
},
.id = I2C_DRIVERID_DS1374,
.attach_adapter = ds1374_attach,
.detach_client = ds1374_detach,
};
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("Randy Vinson <rvinson@mvista.com>");
MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
MODULE_LICENSE("GPL");
