/* * 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> /* * 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_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 rtc_valid_tm(tm); } 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_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 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, const struct i2c_device_id *id) { 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 = 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");