// 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[] = {	{ .name = "max6900" },	{ }};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");