diff options
Diffstat (limited to 'drivers/rtc/rtc-max6900.c')
| -rw-r--r-- | drivers/rtc/rtc-max6900.c | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-max6900.c b/drivers/rtc/rtc-max6900.c new file mode 100644 index 000000000000..eee4ee5bb75a --- /dev/null +++ b/drivers/rtc/rtc-max6900.c @@ -0,0 +1,311 @@ +/* + * 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 */ +#define MAX6900_REG_LEN 8 + +#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */ + +/* + * register read/write commands + */ +#define MAX6900_REG_CONTROL_WRITE 0x8e +#define MAX6900_REG_BURST_READ 0xbf +#define MAX6900_REG_BURST_WRITE 0xbe +#define MAX6900_REG_RESERVED_READ 0x96 + +#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_addr[1] = { MAX6900_REG_BURST_READ }; + struct i2c_msg msgs[2] = { + { + .addr = client->addr, + .flags = 0, /* write */ + .len = sizeof(reg_addr), + .buf = reg_addr + }, + { + .addr = client->addr, + .flags = I2C_M_RD, + .len = MAX6900_REG_LEN, + .buf = buf + } + }; + 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_buf[MAX6900_REG_LEN + 1] = { MAX6900_REG_BURST_WRITE }; + struct i2c_msg msgs[1] = { + { + .addr = client->addr, + .flags = 0, /* write */ + .len = MAX6900_REG_LEN + 1, + .buf = i2c_buf + } + }; + int rc; + + memcpy(&i2c_buf[1], buf, MAX6900_REG_LEN); + + rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); + if (rc != ARRAY_SIZE(msgs)) { + dev_err(&client->dev, "%s: register write failed\n", + __FUNCTION__); + return -EIO; + } + msleep(MAX6900_IDLE_TIME_AFTER_WRITE); + return 0; +} + +static int max6900_i2c_validate_client(struct i2c_client *client) +{ + u8 regs[MAX6900_REG_LEN]; + u8 zero_mask[MAX6900_REG_LEN] = { + 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 < MAX6900_REG_LEN; ++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]) + 100; + 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_YR] = BIN2BCD(tm->tm_year - 100); + regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday); + regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; /* set write protect */ + + 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); |