diff options
Diffstat (limited to 'drivers/i2c/chips/ds1374.c')
| -rw-r--r-- | drivers/i2c/chips/ds1374.c | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/drivers/i2c/chips/ds1374.c b/drivers/i2c/chips/ds1374.c new file mode 100644 index 000000000000..a445736d8838 --- /dev/null +++ b/drivers/i2c/chips/ds1374.c @@ -0,0 +1,260 @@ +/* + * 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> + +#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 DECLARE_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, + .force = 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 */ + + down(&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--); + + up(&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; + + down(&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--); + + up(&ds1374_mutex); + + if (t1 != t2) + dev_warn(&save_client->dev, + "can't confirm time set from rtc chip\n"); +} + +ulong new_time; + +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 = kmalloc(sizeof(struct i2c_client), GFP_KERNEL); + if (!client) + return -ENOMEM; + + memset(client, 0, sizeof(struct i2c_client)); + strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE); + client->flags = I2C_DF_NOTIFY; + 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 = { + .owner = THIS_MODULE, + .name = DS1374_DRV_NAME, + .id = I2C_DRIVERID_DS1374, + .flags = I2C_DF_NOTIFY, + .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"); |
