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linux/drivers/rtc/rtc-max6900.c
Dale Farnsworth 8a2601f6aa rtc: update and use the MAX6900 century byte 
We now read and write the century byte in the max6900 chip.  We probably
don't need to do so on Linux-only system, but it's necessary when the chip
is shared by another OS that uses the century byte.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-21 17:49:17 -07:00

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/*
* rtc class driver for the Maxim MAX6900 chip
*
* Author: Dale Farnsworth <dale@farnsworth.org>
*
* based on previously existing rtc class drivers
*
* 2007 (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.
*/
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/rtc.h>
#include <linux/delay.h>
#define DRV_NAME "max6900"
#define DRV_VERSION "0.1"
/*
* register indices
*/
#define MAX6900_REG_SC 0 /* seconds 00-59 */
#define MAX6900_REG_MN 1 /* minutes 00-59 */
#define MAX6900_REG_HR 2 /* hours 00-23 */
#define MAX6900_REG_DT 3 /* day of month 00-31 */
#define MAX6900_REG_MO 4 /* month 01-12 */
#define MAX6900_REG_DW 5 /* day of week 1-7 */
#define MAX6900_REG_YR 6 /* year 00-99 */
#define MAX6900_REG_CT 7 /* control */
/* register 8 is undocumented */
#define MAX6900_REG_CENTURY 9 /* century */
#define MAX6900_REG_LEN 10
#define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */
#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */
/*
* register read/write commands
*/
#define MAX6900_REG_CONTROL_WRITE 0x8e
#define MAX6900_REG_CENTURY_WRITE 0x92
#define MAX6900_REG_CENTURY_READ 0x93
#define MAX6900_REG_RESERVED_READ 0x96
#define MAX6900_REG_BURST_WRITE 0xbe
#define MAX6900_REG_BURST_READ 0xbf
#define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */
#define MAX6900_I2C_ADDR 0xa0
static unsigned short normal_i2c[] = {
MAX6900_I2C_ADDR >> 1,
I2C_CLIENT_END
};
I2C_CLIENT_INSMOD; /* defines addr_data */
static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
{
u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
struct i2c_msg msgs[4] = {
{
.addr = client->addr,
.flags = 0, /* write */
.len = sizeof(reg_burst_read),
.buf = reg_burst_read
},
{
.addr = client->addr,
.flags = I2C_M_RD,
.len = MAX6900_BURST_LEN,
.buf = buf
},
{
.addr = client->addr,
.flags = 0, /* write */
.len = sizeof(reg_century_read),
.buf = reg_century_read
},
{
.addr = client->addr,
.flags = I2C_M_RD,
.len = sizeof(buf[MAX6900_REG_CENTURY]),
.buf = &buf[MAX6900_REG_CENTURY]
}
};
int rc;
rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
if (rc != ARRAY_SIZE(msgs)) {
dev_err(&client->dev, "%s: register read failed\n",
__FUNCTION__);
return -EIO;
}
return 0;
}
static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
{
u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
struct i2c_msg century_msgs[1] = {
{
.addr = client->addr,
.flags = 0, /* write */
.len = sizeof(i2c_century_buf),
.buf = i2c_century_buf
}
};
u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
struct i2c_msg burst_msgs[1] = {
{
.addr = client->addr,
.flags = 0, /* write */
.len = sizeof(i2c_burst_buf),
.buf = i2c_burst_buf
}
};
int rc;
/*
* We have to make separate calls to i2c_transfer because of
* the need to delay after each write to the chip. Also,
* we write the century byte first, since we set the write-protect
* bit as part of the burst write.
*/
i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
rc = i2c_transfer(client->adapter, century_msgs,
ARRAY_SIZE(century_msgs));
if (rc != ARRAY_SIZE(century_msgs))
goto write_failed;
msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
if (rc != ARRAY_SIZE(burst_msgs))
goto write_failed;
msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
return 0;
write_failed:
dev_err(&client->dev, "%s: register write failed\n",
__FUNCTION__);
return -EIO;
}
static int max6900_i2c_validate_client(struct i2c_client *client)
{
u8 regs[MAX6900_REG_LEN];
u8 zero_mask[] = {
0x80, /* seconds */
0x80, /* minutes */
0x40, /* hours */
0xc0, /* day of month */
0xe0, /* month */
0xf8, /* day of week */
0x00, /* year */
0x7f, /* control */
};
int i;
int rc;
int reserved;
reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ);
if (reserved != 0x07)
return -ENODEV;
rc = max6900_i2c_read_regs(client, regs);
if (rc < 0)
return rc;
for (i = 0; i < ARRAY_SIZE(zero_mask); ++i) {
if (regs[i] & zero_mask[i])
return -ENODEV;
}
return 0;
}
static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
{
int rc;
u8 regs[MAX6900_REG_LEN];
rc = max6900_i2c_read_regs(client, regs);
if (rc < 0)
return rc;
tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]);
tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]);
tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) +
BCD2BIN(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
return 0;
}
static int max6900_i2c_clear_write_protect(struct i2c_client *client)
{
int rc;
rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0);
if (rc < 0) {
dev_err(&client->dev, "%s: control register write failed\n",
__FUNCTION__);
return -EIO;
}
return 0;
}
static int max6900_i2c_set_time(struct i2c_client *client,
struct rtc_time const *tm)
{
u8 regs[MAX6900_REG_LEN];
int rc;
rc = max6900_i2c_clear_write_protect(client);
if (rc < 0)
return rc;
regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec);
regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min);
regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year % 100);
regs[MAX6900_REG_CENTURY] = BIN2BCD((tm->tm_year + 1900) / 100);
/* set write protect */
regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
rc = max6900_i2c_write_regs(client, regs);
if (rc < 0)
return rc;
return 0;
}
static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
return max6900_i2c_read_time(to_i2c_client(dev), tm);
}
static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
return max6900_i2c_set_time(to_i2c_client(dev), tm);
}
static int max6900_attach_adapter(struct i2c_adapter *adapter)
{
return i2c_probe(adapter, &addr_data, max6900_probe);
}
static int max6900_detach_client(struct i2c_client *client)
{
struct rtc_device *const rtc = i2c_get_clientdata(client);
if (rtc)
rtc_device_unregister(rtc);
return i2c_detach_client(client);
}
static struct i2c_driver max6900_driver = {
.driver = {
.name = DRV_NAME,
},
.id = I2C_DRIVERID_MAX6900,
.attach_adapter = max6900_attach_adapter,
.detach_client = max6900_detach_client,
};
static const struct rtc_class_ops max6900_rtc_ops = {
.read_time = max6900_rtc_read_time,
.set_time = max6900_rtc_set_time,
};
static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind)
{
int rc = 0;
struct i2c_client *client = NULL;
struct rtc_device *rtc = NULL;
if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
rc = -ENODEV;
goto failout;
}
client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
if (client == NULL) {
rc = -ENOMEM;
goto failout;
}
client->addr = addr;
client->adapter = adapter;
client->driver = &max6900_driver;
strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE);
if (kind < 0) {
rc = max6900_i2c_validate_client(client);
if (rc < 0)
goto failout;
}
rc = i2c_attach_client(client);
if (rc < 0)
goto failout;
dev_info(&client->dev,
"chip found, driver version " DRV_VERSION "\n");
rtc = rtc_device_register(max6900_driver.driver.name,
&client->dev,
&max6900_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc)) {
rc = PTR_ERR(rtc);
goto failout_detach;
}
i2c_set_clientdata(client, rtc);
return 0;
failout_detach:
i2c_detach_client(client);
failout:
kfree(client);
return rc;
}
static int __init max6900_init(void)
{
return i2c_add_driver(&max6900_driver);
}
static void __exit max6900_exit(void)
{
i2c_del_driver(&max6900_driver);
}
MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);
module_init(max6900_init);
module_exit(max6900_exit);
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