drivers/rtc/rtc-max6900.c

   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 const struct rtc_class_ops max6900_rtc_ops = {
 216         .read_time = max6900_rtc_read_time,
 217         .set_time = max6900_rtc_set_time,
 218 };
 219
 220 static int
 221 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
 222 {
 223         struct rtc_device *rtc;
 224
 225         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 226                 return -ENODEV;
 227
 228         dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
 229
 230         rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
 231                                         &max6900_rtc_ops, THIS_MODULE);
 232         if (IS_ERR(rtc))
 233                 return PTR_ERR(rtc);
 234
 235         i2c_set_clientdata(client, rtc);
 236
 237         return 0;
 238 }
 239
 240 static struct i2c_device_id max6900_id[] = {
 241         { "max6900", 0 },
 242         { }
 243 };
 244
 245 static struct i2c_driver max6900_driver = {
 246         .driver = {
 247                    .name = "rtc-max6900",
 248                    },
 249         .probe = max6900_probe,
 250         .id_table = max6900_id,
 251 };
 252
 253 module_i2c_driver(max6900_driver);
 254
 255 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 256 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
 257 MODULE_LICENSE("GPL");
 258 MODULE_VERSION(DRV_VERSION);