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 /*
  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_rtc_read_time(struct device *dev, struct rtc_time *tm)
 143 {
 144         struct i2c_client *client = to_i2c_client(dev);
 145         int rc;
 146         u8 regs[MAX6900_REG_LEN];
 147
 148         rc = max6900_i2c_read_regs(client, regs);
 149         if (rc < 0)
 150                 return rc;
 151
 152         tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
 153         tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
 154         tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
 155         tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
 156         tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
 157         tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
 158                       bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
 159         tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
 160
 161         return 0;
 162 }
 163
 164 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
 165 {
 166         return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
 167 }
 168
 169 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
 170 {
 171         struct i2c_client *client = to_i2c_client(dev);
 172         u8 regs[MAX6900_REG_LEN];
 173         int rc;
 174
 175         rc = max6900_i2c_clear_write_protect(client);
 176         if (rc < 0)
 177                 return rc;
 178
 179         regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
 180         regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
 181         regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
 182         regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
 183         regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
 184         regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
 185         regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
 186         regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
 187         /* set write protect */
 188         regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
 189
 190         rc = max6900_i2c_write_regs(client, regs);
 191         if (rc < 0)
 192                 return rc;
 193
 194         return 0;
 195 }
 196
 197 static const struct rtc_class_ops max6900_rtc_ops = {
 198         .read_time = max6900_rtc_read_time,
 199         .set_time = max6900_rtc_set_time,
 200 };
 201
 202 static int
 203 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
 204 {
 205         struct rtc_device *rtc;
 206
 207         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 208                 return -ENODEV;
 209
 210         rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
 211                                         &max6900_rtc_ops, THIS_MODULE);
 212         if (IS_ERR(rtc))
 213                 return PTR_ERR(rtc);
 214
 215         i2c_set_clientdata(client, rtc);
 216
 217         return 0;
 218 }
 219
 220 static const struct i2c_device_id max6900_id[] = {
 221         { "max6900", 0 },
 222         { }
 223 };
 224 MODULE_DEVICE_TABLE(i2c, max6900_id);
 225
 226 static struct i2c_driver max6900_driver = {
 227         .driver = {
 228                    .name = "rtc-max6900",
 229                    },
 230         .probe = max6900_probe,
 231         .id_table = max6900_id,
 232 };
 233
 234 module_i2c_driver(max6900_driver);
 235
 236 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 237 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
 238 MODULE_LICENSE("GPL");