1 /* 2 * rtc class driver for the Maxim MAX6900 chip 3 * 4 * Author: Dale Farnsworth <dale@farnsworth.org> 5 * 6 * based on previously existing rtc class drivers 7 * 8 * 2007 (c) MontaVista, Software, Inc. This file is licensed under 9 * the terms of the GNU General Public License version 2. This program 10 * is licensed "as is" without any warranty of any kind, whether express 11 * or implied. 12 */ 13 14 #include <linux/module.h> 15 #include <linux/i2c.h> 16 #include <linux/bcd.h> 17 #include <linux/rtc.h> 18 #include <linux/delay.h> 19 20 /* 21 * register indices 22 */ 23 #define MAX6900_REG_SC 0 /* seconds 00-59 */ 24 #define MAX6900_REG_MN 1 /* minutes 00-59 */ 25 #define MAX6900_REG_HR 2 /* hours 00-23 */ 26 #define MAX6900_REG_DT 3 /* day of month 00-31 */ 27 #define MAX6900_REG_MO 4 /* month 01-12 */ 28 #define MAX6900_REG_DW 5 /* day of week 1-7 */ 29 #define MAX6900_REG_YR 6 /* year 00-99 */ 30 #define MAX6900_REG_CT 7 /* control */ 31 /* register 8 is undocumented */ 32 #define MAX6900_REG_CENTURY 9 /* century */ 33 #define MAX6900_REG_LEN 10 34 35 #define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */ 36 37 #define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */ 38 39 /* 40 * register read/write commands 41 */ 42 #define MAX6900_REG_CONTROL_WRITE 0x8e 43 #define MAX6900_REG_CENTURY_WRITE 0x92 44 #define MAX6900_REG_CENTURY_READ 0x93 45 #define MAX6900_REG_RESERVED_READ 0x96 46 #define MAX6900_REG_BURST_WRITE 0xbe 47 #define MAX6900_REG_BURST_READ 0xbf 48 49 #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */ 50 51 static struct i2c_driver max6900_driver; 52 53 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf) 54 { 55 u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ }; 56 u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ }; 57 struct i2c_msg msgs[4] = { 58 { 59 .addr = client->addr, 60 .flags = 0, /* write */ 61 .len = sizeof(reg_burst_read), 62 .buf = reg_burst_read} 63 , 64 { 65 .addr = client->addr, 66 .flags = I2C_M_RD, 67 .len = MAX6900_BURST_LEN, 68 .buf = buf} 69 , 70 { 71 .addr = client->addr, 72 .flags = 0, /* write */ 73 .len = sizeof(reg_century_read), 74 .buf = reg_century_read} 75 , 76 { 77 .addr = client->addr, 78 .flags = I2C_M_RD, 79 .len = sizeof(buf[MAX6900_REG_CENTURY]), 80 .buf = &buf[MAX6900_REG_CENTURY] 81 } 82 }; 83 int rc; 84 85 rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); 86 if (rc != ARRAY_SIZE(msgs)) { 87 dev_err(&client->dev, "%s: register read failed\n", __func__); 88 return -EIO; 89 } 90 return 0; 91 } 92 93 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf) 94 { 95 u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE }; 96 struct i2c_msg century_msgs[1] = { 97 { 98 .addr = client->addr, 99 .flags = 0, /* write */ 100 .len = sizeof(i2c_century_buf), 101 .buf = i2c_century_buf} 102 }; 103 u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE }; 104 struct i2c_msg burst_msgs[1] = { 105 { 106 .addr = client->addr, 107 .flags = 0, /* write */ 108 .len = sizeof(i2c_burst_buf), 109 .buf = i2c_burst_buf} 110 }; 111 int rc; 112 113 /* 114 * We have to make separate calls to i2c_transfer because of 115 * the need to delay after each write to the chip. Also, 116 * we write the century byte first, since we set the write-protect 117 * bit as part of the burst write. 118 */ 119 i2c_century_buf[1] = buf[MAX6900_REG_CENTURY]; 120 121 rc = i2c_transfer(client->adapter, century_msgs, 122 ARRAY_SIZE(century_msgs)); 123 if (rc != ARRAY_SIZE(century_msgs)) 124 goto write_failed; 125 126 msleep(MAX6900_IDLE_TIME_AFTER_WRITE); 127 128 memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN); 129 130 rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs)); 131 if (rc != ARRAY_SIZE(burst_msgs)) 132 goto write_failed; 133 msleep(MAX6900_IDLE_TIME_AFTER_WRITE); 134 135 return 0; 136 137 write_failed: 138 dev_err(&client->dev, "%s: register write failed\n", __func__); 139 return -EIO; 140 } 141 142 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm) 143 { 144 int rc; 145 u8 regs[MAX6900_REG_LEN]; 146 147 rc = max6900_i2c_read_regs(client, regs); 148 if (rc < 0) 149 return rc; 150 151 tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]); 152 tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]); 153 tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f); 154 tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]); 155 tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1; 156 tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) + 157 bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900; 158 tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]); 159 160 return rtc_valid_tm(tm); 161 } 162 163 static int max6900_i2c_clear_write_protect(struct i2c_client *client) 164 { 165 return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0); 166 } 167 168 static int 169 max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm) 170 { 171 u8 regs[MAX6900_REG_LEN]; 172 int rc; 173 174 rc = max6900_i2c_clear_write_protect(client); 175 if (rc < 0) 176 return rc; 177 178 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec); 179 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min); 180 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour); 181 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday); 182 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1); 183 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday); 184 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100); 185 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100); 186 /* set write protect */ 187 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; 188 189 rc = max6900_i2c_write_regs(client, regs); 190 if (rc < 0) 191 return rc; 192 193 return 0; 194 } 195 196 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) 197 { 198 return max6900_i2c_read_time(to_i2c_client(dev), tm); 199 } 200 201 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) 202 { 203 return max6900_i2c_set_time(to_i2c_client(dev), tm); 204 } 205 206 static const struct rtc_class_ops max6900_rtc_ops = { 207 .read_time = max6900_rtc_read_time, 208 .set_time = max6900_rtc_set_time, 209 }; 210 211 static int 212 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id) 213 { 214 struct rtc_device *rtc; 215 216 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 217 return -ENODEV; 218 219 rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name, 220 &max6900_rtc_ops, THIS_MODULE); 221 if (IS_ERR(rtc)) 222 return PTR_ERR(rtc); 223 224 i2c_set_clientdata(client, rtc); 225 226 return 0; 227 } 228 229 static struct i2c_device_id max6900_id[] = { 230 { "max6900", 0 }, 231 { } 232 }; 233 MODULE_DEVICE_TABLE(i2c, max6900_id); 234 235 static struct i2c_driver max6900_driver = { 236 .driver = { 237 .name = "rtc-max6900", 238 }, 239 .probe = max6900_probe, 240 .id_table = max6900_id, 241 }; 242 243 module_i2c_driver(max6900_driver); 244 245 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); 246 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>"); 247 MODULE_LICENSE("GPL"); 248