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 return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0); 168 } 169 170 static int 171 max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm) 172 { 173 u8 regs[MAX6900_REG_LEN]; 174 int rc; 175 176 rc = max6900_i2c_clear_write_protect(client); 177 if (rc < 0) 178 return rc; 179 180 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec); 181 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min); 182 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour); 183 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday); 184 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1); 185 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday); 186 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100); 187 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100); 188 /* set write protect */ 189 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; 190 191 rc = max6900_i2c_write_regs(client, regs); 192 if (rc < 0) 193 return rc; 194 195 return 0; 196 } 197 198 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) 199 { 200 return max6900_i2c_read_time(to_i2c_client(dev), tm); 201 } 202 203 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) 204 { 205 return max6900_i2c_set_time(to_i2c_client(dev), tm); 206 } 207 208 static const struct rtc_class_ops max6900_rtc_ops = { 209 .read_time = max6900_rtc_read_time, 210 .set_time = max6900_rtc_set_time, 211 }; 212 213 static int 214 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id) 215 { 216 struct rtc_device *rtc; 217 218 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) 219 return -ENODEV; 220 221 dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n"); 222 223 rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name, 224 &max6900_rtc_ops, THIS_MODULE); 225 if (IS_ERR(rtc)) 226 return PTR_ERR(rtc); 227 228 i2c_set_clientdata(client, rtc); 229 230 return 0; 231 } 232 233 static struct i2c_device_id max6900_id[] = { 234 { "max6900", 0 }, 235 { } 236 }; 237 238 static struct i2c_driver max6900_driver = { 239 .driver = { 240 .name = "rtc-max6900", 241 }, 242 .probe = max6900_probe, 243 .id_table = max6900_id, 244 }; 245 246 module_i2c_driver(max6900_driver); 247 248 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver"); 249 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>"); 250 MODULE_LICENSE("GPL"); 251 MODULE_VERSION(DRV_VERSION); 252