drivers/rtc/rtc-max6900.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * rtc class driver for the Maxim MAX6900 chip
   4  *
   5  * Copyright (c) 2007 MontaVista, Software, Inc.
   6  *
   7  * Author: Dale Farnsworth <dale@farnsworth.org>
   8  *
   9  * based on previously existing rtc class drivers
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/i2c.h>
  14 #include <linux/bcd.h>
  15 #include <linux/rtc.h>
  16 #include <linux/delay.h>
  17
  18 /*
  19  * register indices
  20  */
  21 #define MAX6900_REG_SC                  0       /* seconds      00-59 */
  22 #define MAX6900_REG_MN                  1       /* minutes      00-59 */
  23 #define MAX6900_REG_HR                  2       /* hours        00-23 */
  24 #define MAX6900_REG_DT                  3       /* day of month 00-31 */
  25 #define MAX6900_REG_MO                  4       /* month        01-12 */
  26 #define MAX6900_REG_DW                  5       /* day of week   1-7  */
  27 #define MAX6900_REG_YR                  6       /* year         00-99 */
  28 #define MAX6900_REG_CT                  7       /* control */
  29                                                 /* register 8 is undocumented */
  30 #define MAX6900_REG_CENTURY             9       /* century */
  31 #define MAX6900_REG_LEN                 10
  32
  33 #define MAX6900_BURST_LEN               8       /* can burst r/w first 8 regs */
  34
  35 #define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
  36
  37 /*
  38  * register read/write commands
  39  */
  40 #define MAX6900_REG_CONTROL_WRITE       0x8e
  41 #define MAX6900_REG_CENTURY_WRITE       0x92
  42 #define MAX6900_REG_CENTURY_READ        0x93
  43 #define MAX6900_REG_RESERVED_READ       0x96
  44 #define MAX6900_REG_BURST_WRITE         0xbe
  45 #define MAX6900_REG_BURST_READ          0xbf
  46
  47 #define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
  48
  49 static struct i2c_driver max6900_driver;
  50
  51 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
  52 {
  53         u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
  54         u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
  55         struct i2c_msg msgs[4] = {
  56                 {
  57                  .addr = client->addr,
  58                  .flags = 0,    /* write */
  59                  .len = sizeof(reg_burst_read),
  60                  .buf = reg_burst_read}
  61                 ,
  62                 {
  63                  .addr = client->addr,
  64                  .flags = I2C_M_RD,
  65                  .len = MAX6900_BURST_LEN,
  66                  .buf = buf}
  67                 ,
  68                 {
  69                  .addr = client->addr,
  70                  .flags = 0,    /* write */
  71                  .len = sizeof(reg_century_read),
  72                  .buf = reg_century_read}
  73                 ,
  74                 {
  75                  .addr = client->addr,
  76                  .flags = I2C_M_RD,
  77                  .len = sizeof(buf[MAX6900_REG_CENTURY]),
  78                  .buf = &buf[MAX6900_REG_CENTURY]
  79                  }
  80         };
  81         int rc;
  82
  83         rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  84         if (rc != ARRAY_SIZE(msgs)) {
  85                 dev_err(&client->dev, "%s: register read failed\n", __func__);
  86                 return -EIO;
  87         }
  88         return 0;
  89 }
  90
  91 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
  92 {
  93         u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
  94         struct i2c_msg century_msgs[1] = {
  95                 {
  96                  .addr = client->addr,
  97                  .flags = 0,    /* write */
  98                  .len = sizeof(i2c_century_buf),
  99                  .buf = i2c_century_buf}
 100         };
 101         u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
 102         struct i2c_msg burst_msgs[1] = {
 103                 {
 104                  .addr = client->addr,
 105                  .flags = 0,    /* write */
 106                  .len = sizeof(i2c_burst_buf),
 107                  .buf = i2c_burst_buf}
 108         };
 109         int rc;
 110
 111         /*
 112          * We have to make separate calls to i2c_transfer because of
 113          * the need to delay after each write to the chip.  Also,
 114          * we write the century byte first, since we set the write-protect
 115          * bit as part of the burst write.
 116          */
 117         i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
 118
 119         rc = i2c_transfer(client->adapter, century_msgs,
 120                           ARRAY_SIZE(century_msgs));
 121         if (rc != ARRAY_SIZE(century_msgs))
 122                 goto write_failed;
 123
 124         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 125
 126         memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
 127
 128         rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
 129         if (rc != ARRAY_SIZE(burst_msgs))
 130                 goto write_failed;
 131         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
 132
 133         return 0;
 134
 135  write_failed:
 136         dev_err(&client->dev, "%s: register write failed\n", __func__);
 137         return -EIO;
 138 }
 139
 140 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
 141 {
 142         struct i2c_client *client = to_i2c_client(dev);
 143         int rc;
 144         u8 regs[MAX6900_REG_LEN];
 145
 146         rc = max6900_i2c_read_regs(client, regs);
 147         if (rc < 0)
 148                 return rc;
 149
 150         tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
 151         tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
 152         tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
 153         tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
 154         tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
 155         tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
 156                       bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
 157         tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
 158
 159         return 0;
 160 }
 161
 162 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
 163 {
 164         return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
 165 }
 166
 167 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
 168 {
 169         struct i2c_client *client = to_i2c_client(dev);
 170         u8 regs[MAX6900_REG_LEN];
 171         int rc;
 172
 173         rc = max6900_i2c_clear_write_protect(client);
 174         if (rc < 0)
 175                 return rc;
 176
 177         regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
 178         regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
 179         regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
 180         regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
 181         regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
 182         regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
 183         regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
 184         regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
 185         /* set write protect */
 186         regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
 187
 188         rc = max6900_i2c_write_regs(client, regs);
 189         if (rc < 0)
 190                 return rc;
 191
 192         return 0;
 193 }
 194
 195 static const struct rtc_class_ops max6900_rtc_ops = {
 196         .read_time = max6900_rtc_read_time,
 197         .set_time = max6900_rtc_set_time,
 198 };
 199
 200 static int max6900_probe(struct i2c_client *client)
 201 {
 202         struct rtc_device *rtc;
 203
 204         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 205                 return -ENODEV;
 206
 207         rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
 208                                         &max6900_rtc_ops, THIS_MODULE);
 209         if (IS_ERR(rtc))
 210                 return PTR_ERR(rtc);
 211
 212         i2c_set_clientdata(client, rtc);
 213
 214         return 0;
 215 }
 216
 217 static const struct i2c_device_id max6900_id[] = {
 218         { "max6900", 0 },
 219         { }
 220 };
 221 MODULE_DEVICE_TABLE(i2c, max6900_id);
 222
 223 static struct i2c_driver max6900_driver = {
 224         .driver = {
 225                    .name = "rtc-max6900",
 226                    },
 227         .probe = max6900_probe,
 228         .id_table = max6900_id,
 229 };
 230
 231 module_i2c_driver(max6900_driver);
 232
 233 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
 234 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
 235 MODULE_LICENSE("GPL");