1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * rtc class driver for the Maxim MAX6900 chip 4 * 5 * Copyright (c) 2007 MontaVista, Software, Inc. 6 * 7 * Author: Dale Farnsworth <dale@farnsworth.org> 8 * 9 * based on previously existing rtc class drivers 10 */ 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 indices 20 */ 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 10 32 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 commands 39 */ 40 #define MAX6900_REG_CONTROL_WRITE 0x8e 41 #define MAX6900_REG_CENTURY_WRITE 0x92 42 #define MAX6900_REG_CENTURY_READ 0x93 43 #define MAX6900_REG_RESERVED_READ 0x96 44 #define MAX6900_REG_BURST_WRITE 0xbe 45 #define MAX6900_REG_BURST_READ 0xbf 46 47 #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */ 48 49 static struct i2c_driver max6900_driver; 50 51 static 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 91 static 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 of 113 * the need to delay after each write to the chip. Also, 114 * we write the century byte first, since we set the write-protect 115 * 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 } 139 140 static 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 } 161 162 static 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 } 166 167 static 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 } 194 195 static const struct rtc_class_ops max6900_rtc_ops = { 196 .read_time = max6900_rtc_read_time, 197 .set_time = max6900_rtc_set_time, 198 }; 199 200 static 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 } 216 217 static const struct i2c_device_id max6900_id[] = { 218 { "max6900", 0 }, 219 { } 220 }; 221 MODULE_DEVICE_TABLE(i2c, max6900_id); 222 223 static struct i2c_driver max6900_driver = { 224 .driver = { 225 .name = "rtc-max6900", 226 }, 227 .probe = max6900_probe, 228 .id_table = max6900_id, 229 }; 230 231 module_i2c_driver(max6900_driver); 232 233 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); 234 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>"); 235 MODULE_LICENSE("GPL"); 236