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 #define DRV_VERSION "0.2" 21 22 /* 23 * register indices 24 */ 25 #define MAX6900_REG_SC 0 /* seconds 00-59 */ 26 #define MAX6900_REG_MN 1 /* minutes 00-59 */ 27 #define MAX6900_REG_HR 2 /* hours 00-23 */ 28 #define MAX6900_REG_DT 3 /* day of month 00-31 */ 29 #define MAX6900_REG_MO 4 /* month 01-12 */ 30 #define MAX6900_REG_DW 5 /* day of week 1-7 */ 31 #define MAX6900_REG_YR 6 /* year 00-99 */ 32 #define MAX6900_REG_CT 7 /* control */ 33 /* register 8 is undocumented */ 34 #define MAX6900_REG_CENTURY 9 /* century */ 35 #define MAX6900_REG_LEN 10 36 37 #define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */ 38 39 #define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */ 40 41 /* 42 * register read/write commands 43 */ 44 #define MAX6900_REG_CONTROL_WRITE 0x8e 45 #define MAX6900_REG_CENTURY_WRITE 0x92 46 #define MAX6900_REG_CENTURY_READ 0x93 47 #define MAX6900_REG_RESERVED_READ 0x96 48 #define MAX6900_REG_BURST_WRITE 0xbe 49 #define MAX6900_REG_BURST_READ 0xbf 50 51 #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */ 52 53 static struct i2c_driver max6900_driver; 54 55 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf) 56 { 57 u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ }; 58 u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ }; 59 struct i2c_msg msgs[4] = { 60 { 61 .addr = client->addr, 62 .flags = 0, /* write */ 63 .len = sizeof(reg_burst_read), 64 .buf = reg_burst_read} 65 , 66 { 67 .addr = client->addr, 68 .flags = I2C_M_RD, 69 .len = MAX6900_BURST_LEN, 70 .buf = buf} 71 , 72 { 73 .addr = client->addr, 74 .flags = 0, /* write */ 75 .len = sizeof(reg_century_read), 76 .buf = reg_century_read} 77 , 78 { 79 .addr = client->addr, 80 .flags = I2C_M_RD, 81 .len = sizeof(buf[MAX6900_REG_CENTURY]), 82 .buf = &buf[MAX6900_REG_CENTURY] 83 } 84 }; 85 int rc; 86 87 rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs)); 88 if (rc != ARRAY_SIZE(msgs)) { 89 dev_err(&client->dev, "%s: register read failed\n", __func__); 90 return -EIO; 91 } 92 return 0; 93 } 94 95 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf) 96 { 97 u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE }; 98 struct i2c_msg century_msgs[1] = { 99 { 100 .addr = client->addr, 101 .flags = 0, /* write */ 102 .len = sizeof(i2c_century_buf), 103 .buf = i2c_century_buf} 104 }; 105 u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE }; 106 struct i2c_msg burst_msgs[1] = { 107 { 108 .addr = client->addr, 109 .flags = 0, /* write */ 110 .len = sizeof(i2c_burst_buf), 111 .buf = i2c_burst_buf} 112 }; 113 int rc; 114 115 /* 116 * We have to make separate calls to i2c_transfer because of 117 * the need to delay after each write to the chip. Also, 118 * we write the century byte first, since we set the write-protect 119 * bit as part of the burst write. 120 */ 121 i2c_century_buf[1] = buf[MAX6900_REG_CENTURY]; 122 123 rc = i2c_transfer(client->adapter, century_msgs, 124 ARRAY_SIZE(century_msgs)); 125 if (rc != ARRAY_SIZE(century_msgs)) 126 goto write_failed; 127 128 msleep(MAX6900_IDLE_TIME_AFTER_WRITE); 129 130 memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN); 131 132 rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs)); 133 if (rc != ARRAY_SIZE(burst_msgs)) 134 goto write_failed; 135 msleep(MAX6900_IDLE_TIME_AFTER_WRITE); 136 137 return 0; 138 139 write_failed: 140 dev_err(&client->dev, "%s: register write failed\n", __func__); 141 return -EIO; 142 } 143 144 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm) 145 { 146 int rc; 147 u8 regs[MAX6900_REG_LEN]; 148 149 rc = max6900_i2c_read_regs(client, regs); 150 if (rc < 0) 151 return rc; 152 153 tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]); 154 tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]); 155 tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f); 156 tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]); 157 tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1; 158 tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) + 159 bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900; 160 tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]); 161 162 return rtc_valid_tm(tm); 163 } 164 165 static int max6900_i2c_clear_write_protect(struct i2c_client *client) 166 { 167 int rc; 168 rc = i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0); 169 if (rc < 0) { 170 dev_err(&client->dev, "%s: control register write failed\n", 171 __func__); 172 return -EIO; 173 } 174 return 0; 175 } 176 177 static int 178 max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm) 179 { 180 u8 regs[MAX6900_REG_LEN]; 181 int rc; 182 183 rc = max6900_i2c_clear_write_protect(client); 184 if (rc < 0) 185 return rc; 186 187 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec); 188 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min); 189 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour); 190 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday); 191 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1); 192 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday); 193 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100); 194 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100); 195 /* set write protect */ 196 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; 197 198 rc = max6900_i2c_write_regs(client, regs); 199 if (rc < 0) 200 return rc; 201 202 return 0; 203 } 204 205 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) 206 { 207 return max6900_i2c_read_time(to_i2c_client(dev), tm); 208 } 209 210 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) 211 { 212 return max6900_i2c_set_time(to_i2c_client(dev), tm); 213 } 214 215 static int max6900_remove(struct i2c_client *client) 216 { 217 struct rtc_device *rtc = i2c_get_clientdata(client); 218 219 if (rtc) 220 rtc_device_unregister(rtc); 221 222 return 0; 223 } 224 225 static const struct rtc_class_ops max6900_rtc_ops = { 226 .read_time = max6900_rtc_read_time, 227 .set_time = max6900_rtc_set_time, 228 }; 229 230 static int 231 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id) 232 { 233 struct rtc_device *rtc; 234 235 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 236 return -ENODEV; 237 238 dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n"); 239 240 rtc = rtc_device_register(max6900_driver.driver.name, 241 &client->dev, &max6900_rtc_ops, THIS_MODULE); 242 if (IS_ERR(rtc)) 243 return PTR_ERR(rtc); 244 245 i2c_set_clientdata(client, rtc); 246 247 return 0; 248 } 249 250 static struct i2c_device_id max6900_id[] = { 251 { "max6900", 0 }, 252 { } 253 }; 254 255 static struct i2c_driver max6900_driver = { 256 .driver = { 257 .name = "rtc-max6900", 258 }, 259 .probe = max6900_probe, 260 .remove = max6900_remove, 261 .id_table = max6900_id, 262 }; 263 264 static int __init max6900_init(void) 265 { 266 return i2c_add_driver(&max6900_driver); 267 } 268 269 static void __exit max6900_exit(void) 270 { 271 i2c_del_driver(&max6900_driver); 272 } 273 274 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); 275 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>"); 276 MODULE_LICENSE("GPL"); 277 MODULE_VERSION(DRV_VERSION); 278 279 module_init(max6900_init); 280 module_exit(max6900_exit); 281