diff options
Diffstat (limited to 'drivers/rtc/rtc-max6900.c')
| -rw-r--r-- | drivers/rtc/rtc-max6900.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-max6900.c b/drivers/rtc/rtc-max6900.c new file mode 100644 index 000000000..0a33851cc --- /dev/null +++ b/drivers/rtc/rtc-max6900.c @@ -0,0 +1,235 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * rtc class driver for the Maxim MAX6900 chip + * + * Copyright (c) 2007 MontaVista, Software, Inc. + * + * Author: Dale Farnsworth <dale@farnsworth.org> + * + * based on previously existing rtc class drivers + */ + +#include <linux/module.h> +#include <linux/i2c.h> +#include <linux/bcd.h> +#include <linux/rtc.h> +#include <linux/delay.h> + +/* + * 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 */ + +static struct i2c_driver max6900_driver; + +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", __func__); + 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", __func__); + return -EIO; +} + +static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + struct i2c_client *client = to_i2c_client(dev); + 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) +{ + return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0); +} + +static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct i2c_client *client = to_i2c_client(dev); + 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 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_client *client) +{ + struct rtc_device *rtc; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) + return -ENODEV; + + rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name, + &max6900_rtc_ops, THIS_MODULE); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + i2c_set_clientdata(client, rtc); + + return 0; +} + +static const struct i2c_device_id max6900_id[] = { + { "max6900", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, max6900_id); + +static struct i2c_driver max6900_driver = { + .driver = { + .name = "rtc-max6900", + }, + .probe_new = max6900_probe, + .id_table = max6900_id, +}; + +module_i2c_driver(max6900_driver); + +MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); +MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>"); +MODULE_LICENSE("GPL"); |