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- /*
- * rtc-ds13307.c - RTC driver for the DS1307 and DS13307 I2C chips.
- *
- * Copyright (C) 2018 Helmut Pozimski
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
- #include <linux/module.h>
- #include <linux/rtc.h>
- #include <linux/i2c.h>
- #include <linux/bcd.h>
- #define M_NAME "rtc-ds13307" /* Module name */
- #define DEVICE_DS1307 1
- #define DEVICE_DS1337 2
- #define COMMON_SEC 0x00
- #define COMMON_MIN 0x01
- #define COMMON_HOUR 0x02
- #define COMMON_DAY 0x03
- #define COMMON_DATE 0x04
- #define COMMON_MONTH 0x05
- #define COMMON_YEAR 0x06
- #define COMMON_HIGH_BIT 0x80
- #define DS1307_MAX_ADDR 0x3F
- #define DS1337_HOUR 0x02
- #define DS1337_DATE 0x03
- #define DS1337_CTL 0x0E
- #define DS1337_STAT 0x0F
- static int model_detected;
- static struct i2c_driver ds13307_driver;
- /* Reads a specified number of bytes via i2c, returns 0 on success */
- static int ds13307_read_bytes(struct i2c_client *client,
- unsigned char *addr, u8 *byte, int length) {
- int r;
- struct i2c_msg msgs[] = {
- {
- .addr = client->addr,
- .len = 1,
- .buf = addr
- },
- {
- .addr = client->addr,
- .flags = I2C_M_RD,
- .len = length,
- .buf = byte
- }
- };
- r = i2c_transfer(client->adapter, msgs, 2);
- if (r == 2) {
- return 0;
- } else {
- return r;
- }
- }
- static int ds13307_read_time(struct device *dev, struct rtc_time *time) {
- struct i2c_client *client;
- int r;
- int h12 = 0;
- u8 buf[7], stopbit;
- unsigned char addr = COMMON_SEC;
- client = to_i2c_client(dev);
- r = ds13307_read_bytes(client, &addr, buf, 7);
- if (model_detected == DEVICE_DS1337) {
- addr = DS1337_STAT;
- r = ds13307_read_bytes(client, &addr, &stopbit, 1);
- stopbit = stopbit & COMMON_HIGH_BIT;
- } else {
- stopbit = buf[COMMON_SEC] & 0x40;
- }
- if (r) {
- return -EIO;
- }
- if (stopbit) {
- printk(KERN_ERR "%s: Oscillator stop bit is set, values read from rtc device cannot be trusted\n", M_NAME);
- return -EINVAL;
- }
- if (buf[COMMON_HOUR] & 0x40) {
- buf[COMMON_HOUR] = buf[COMMON_HOUR] ^ 0x40;
- if (buf[COMMON_HOUR] & 0x20) {
- buf[COMMON_HOUR] = buf[COMMON_HOUR] ^ 0x20;
- h12 = 1;
- }
- }
- if (model_detected == DEVICE_DS1337) {
- buf[COMMON_MONTH] = buf[COMMON_MONTH] ^ COMMON_HIGH_BIT;
- }
- time->tm_sec = bcd2bin(buf[COMMON_SEC]);
- time->tm_min = bcd2bin(buf[COMMON_MIN]);
- time->tm_hour = bcd2bin(buf[COMMON_HOUR]);
- if(h12) {
- time->tm_hour += 12;
- }
- time->tm_mday = bcd2bin(buf[COMMON_DATE]);
- time->tm_wday = bcd2bin(buf[COMMON_DAY]);
- time->tm_mon = bcd2bin(buf[COMMON_MONTH]) - 1 ;
- time->tm_year = bcd2bin(buf[COMMON_YEAR]) + 100;
- return 0;
- }
- static const struct rtc_class_ops ds13307_rtc_ops = {
- .read_time = ds13307_read_time,
- };
- /* Performs the device detection to distinguish between the
- * DS1307 and DS1337 chips. Returns the defined device ID or
- * -1 on failure
- */
- static int ds13307_detect_device(struct i2c_client *client) {
- u8 data;
- int result;
- unsigned char addr = DS1307_MAX_ADDR;
- result = ds13307_read_bytes(client, &addr, &data, 1);
- if (!result) {
- printk(KERN_INFO "%s: Detected device DS1307\n", M_NAME);
- return DEVICE_DS1307;
- }
- addr = DS1337_CTL;
- result = ds13307_read_bytes(client, &addr, &data, 1);
- if (!result) {
- printk(KERN_INFO "%s: Detected device DS1337\n", M_NAME);
- return DEVICE_DS1337;
- }
- printk(KERN_ERR "%s: Could not talk to I2C device at addr %x, is it connected?\n",
- M_NAME, client->addr);
- return -1;
- }
- /* The oscillator is stopped for both chips when power is first applied,
- * therefore this function checks its status and clears the stop bit.
- */
- static int ds13307_start_oscillator(struct i2c_client *client) {
- u8 data;
- int r, v;
- unsigned char addr;
- char buf[2];
- if (model_detected == DEVICE_DS1307) {
- addr = COMMON_SEC;
- } else {
- addr = DS1337_STAT;
- }
- r = ds13307_read_bytes(client, &addr, &data, 1);
- if (data & COMMON_HIGH_BIT) {
- buf[0] = addr;
- buf[1] = data ^ COMMON_HIGH_BIT;
- v = i2c_master_send(client, buf, 2);
- if (v == 2) {
- printk(KERN_DEBUG "%s: oscillator stop bit successfully cleared\n", M_NAME);
- }
- } else {
- v = 2;
- }
- if ((r<0) || (v!=2)) {
- return -EIO;
- }
- return 0;
- }
- static int ds13307_probe(struct i2c_client *client,
- const struct i2c_device_id *id) {
- struct rtc_device *rtc;
- model_detected = ds13307_detect_device(client);
- if ((model_detected != DEVICE_DS1307) && (model_detected != DEVICE_DS1337)) {
- return -EIO;
- }
- if (ds13307_start_oscillator(client)) {
- printk(KERN_ERR "%s: failed to initialize the oscillator\n", M_NAME);
- return -EIO;
- }
- rtc = devm_rtc_device_register(&client->dev, ds13307_driver.driver.name,
- &ds13307_rtc_ops, THIS_MODULE);
- if (IS_ERR(rtc)) {
- return PTR_ERR(rtc);
- }
- i2c_set_clientdata(client,rtc);
- return 0;
- }
- static struct i2c_device_id ds13307_idtable[] = {
- { "ds1307", 0 }, {}
- };
- MODULE_DEVICE_TABLE(i2c, ds13307_idtable);
- static struct of_device_id ds13307_of_match[] = {
- { .compatible = "dallas,ds1307" },
- {}
- };
- MODULE_DEVICE_TABLE(of, ds13307_of_match);
- static struct i2c_driver ds13307_driver = {
- .driver = {
- .name = "rtc-ds13307",
- .of_match_table = of_match_ptr(ds13307_of_match),
- .owner = THIS_MODULE
- },
- .id_table = ds13307_idtable,
- .probe = ds13307_probe,
- };
- module_i2c_driver(ds13307_driver);
- MODULE_AUTHOR("Helmut Pozimski <helmut@pozimski.eu>");
- MODULE_DESCRIPTION("DS1307 and DS1337 RTC driver");
- MODULE_LICENSE("GPL");
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