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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * rtc class driver for the Maxim MAX6900 chip4 *5 * Copyright (c) 2007 MontaVista, Software, Inc.6 *7 * Author: Dale Farnsworth <dale@farnsworth.org>8 *9 * based on previously existing rtc class drivers10 */11 12#include <linux/module.h>13#include <linux/i2c.h>14#include <linux/bcd.h>15#include <linux/rtc.h>16#include <linux/delay.h>17 18/*19 * register indices20 */21#define MAX6900_REG_SC 0 /* seconds 00-59 */22#define MAX6900_REG_MN 1 /* minutes 00-59 */23#define MAX6900_REG_HR 2 /* hours 00-23 */24#define MAX6900_REG_DT 3 /* day of month 00-31 */25#define MAX6900_REG_MO 4 /* month 01-12 */26#define MAX6900_REG_DW 5 /* day of week 1-7 */27#define MAX6900_REG_YR 6 /* year 00-99 */28#define MAX6900_REG_CT 7 /* control */29 /* register 8 is undocumented */30#define MAX6900_REG_CENTURY 9 /* century */31#define MAX6900_REG_LEN 1032 33#define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */34 35#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */36 37/*38 * register read/write commands39 */40#define MAX6900_REG_CONTROL_WRITE 0x8e41#define MAX6900_REG_CENTURY_WRITE 0x9242#define MAX6900_REG_CENTURY_READ 0x9343#define MAX6900_REG_RESERVED_READ 0x9644#define MAX6900_REG_BURST_WRITE 0xbe45#define MAX6900_REG_BURST_READ 0xbf46 47#define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */48 49static struct i2c_driver max6900_driver;50 51static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)52{53 u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };54 u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };55 struct i2c_msg msgs[4] = {56 {57 .addr = client->addr,58 .flags = 0, /* write */59 .len = sizeof(reg_burst_read),60 .buf = reg_burst_read}61 ,62 {63 .addr = client->addr,64 .flags = I2C_M_RD,65 .len = MAX6900_BURST_LEN,66 .buf = buf}67 ,68 {69 .addr = client->addr,70 .flags = 0, /* write */71 .len = sizeof(reg_century_read),72 .buf = reg_century_read}73 ,74 {75 .addr = client->addr,76 .flags = I2C_M_RD,77 .len = sizeof(buf[MAX6900_REG_CENTURY]),78 .buf = &buf[MAX6900_REG_CENTURY]79 }80 };81 int rc;82 83 rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));84 if (rc != ARRAY_SIZE(msgs)) {85 dev_err(&client->dev, "%s: register read failed\n", __func__);86 return -EIO;87 }88 return 0;89}90 91static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)92{93 u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };94 struct i2c_msg century_msgs[1] = {95 {96 .addr = client->addr,97 .flags = 0, /* write */98 .len = sizeof(i2c_century_buf),99 .buf = i2c_century_buf}100 };101 u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };102 struct i2c_msg burst_msgs[1] = {103 {104 .addr = client->addr,105 .flags = 0, /* write */106 .len = sizeof(i2c_burst_buf),107 .buf = i2c_burst_buf}108 };109 int rc;110 111 /*112 * We have to make separate calls to i2c_transfer because of113 * the need to delay after each write to the chip. Also,114 * we write the century byte first, since we set the write-protect115 * bit as part of the burst write.116 */117 i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];118 119 rc = i2c_transfer(client->adapter, century_msgs,120 ARRAY_SIZE(century_msgs));121 if (rc != ARRAY_SIZE(century_msgs))122 goto write_failed;123 124 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);125 126 memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);127 128 rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));129 if (rc != ARRAY_SIZE(burst_msgs))130 goto write_failed;131 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);132 133 return 0;134 135 write_failed:136 dev_err(&client->dev, "%s: register write failed\n", __func__);137 return -EIO;138}139 140static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)141{142 struct i2c_client *client = to_i2c_client(dev);143 int rc;144 u8 regs[MAX6900_REG_LEN];145 146 rc = max6900_i2c_read_regs(client, regs);147 if (rc < 0)148 return rc;149 150 tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);151 tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);152 tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);153 tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);154 tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;155 tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +156 bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;157 tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);158 159 return 0;160}161 162static int max6900_i2c_clear_write_protect(struct i2c_client *client)163{164 return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);165}166 167static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)168{169 struct i2c_client *client = to_i2c_client(dev);170 u8 regs[MAX6900_REG_LEN];171 int rc;172 173 rc = max6900_i2c_clear_write_protect(client);174 if (rc < 0)175 return rc;176 177 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);178 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);179 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);180 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);181 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);182 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);183 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);184 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);185 /* set write protect */186 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;187 188 rc = max6900_i2c_write_regs(client, regs);189 if (rc < 0)190 return rc;191 192 return 0;193}194 195static const struct rtc_class_ops max6900_rtc_ops = {196 .read_time = max6900_rtc_read_time,197 .set_time = max6900_rtc_set_time,198};199 200static int max6900_probe(struct i2c_client *client)201{202 struct rtc_device *rtc;203 204 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))205 return -ENODEV;206 207 rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,208 &max6900_rtc_ops, THIS_MODULE);209 if (IS_ERR(rtc))210 return PTR_ERR(rtc);211 212 i2c_set_clientdata(client, rtc);213 214 return 0;215}216 217static const struct i2c_device_id max6900_id[] = {218 { "max6900" },219 { }220};221MODULE_DEVICE_TABLE(i2c, max6900_id);222 223static struct i2c_driver max6900_driver = {224 .driver = {225 .name = "rtc-max6900",226 },227 .probe = max6900_probe,228 .id_table = max6900_id,229};230 231module_i2c_driver(max6900_driver);232 233MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");234MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");235MODULE_LICENSE("GPL");236