drivers/rtc/rtc-ds1672.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * An rtc/i2c driver for the Dallas DS1672
   4  * Copyright 2005-06 Tower Technologies
   5  *
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  */
   8
   9 #include <linux/i2c.h>
  10 #include <linux/rtc.h>
  11 #include <linux/module.h>
  12
  13 /* Registers */
  14
  15 #define DS1672_REG_CNT_BASE     0
  16 #define DS1672_REG_CONTROL      4
  17 #define DS1672_REG_TRICKLE      5
  18
  19 #define DS1672_REG_CONTROL_EOSC 0x80
  20
  21 /*
  22  * In the routines that deal directly with the ds1672 hardware, we use
  23  * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch
  24  * Time is set to UTC.
  25  */
  26 static int ds1672_read_time(struct device *dev, struct rtc_time *tm)
  27 {
  28         struct i2c_client *client = to_i2c_client(dev);
  29         unsigned long time;
  30         unsigned char addr = DS1672_REG_CONTROL;
  31         unsigned char buf[4];
  32
  33         struct i2c_msg msgs[] = {
  34                 {/* setup read ptr */
  35                         .addr = client->addr,
  36                         .len = 1,
  37                         .buf = &addr
  38                 },
  39                 {/* read date */
  40                         .addr = client->addr,
  41                         .flags = I2C_M_RD,
  42                         .len = 1,
  43                         .buf = buf
  44                 },
  45         };
  46
  47         /* read control register */
  48         if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
  49                 dev_warn(&client->dev, "Unable to read the control register\n");
  50                 return -EIO;
  51         }
  52
  53         if (buf[0] & DS1672_REG_CONTROL_EOSC) {
  54                 dev_warn(&client->dev, "Oscillator not enabled. Set time to enable.\n");
  55                 return -EINVAL;
  56         }
  57
  58         addr = DS1672_REG_CNT_BASE;
  59         msgs[1].len = 4;
  60
  61         /* read date registers */
  62         if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
  63                 dev_err(&client->dev, "%s: read error\n", __func__);
  64                 return -EIO;
  65         }
  66
  67         dev_dbg(&client->dev,
  68                 "%s: raw read data - counters=%02x,%02x,%02x,%02x\n",
  69                 __func__, buf[0], buf[1], buf[2], buf[3]);
  70
  71         time = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
  72                (buf[1] << 8) | buf[0];
  73
  74         rtc_time64_to_tm(time, tm);
  75
  76         dev_dbg(&client->dev, "%s: tm is %ptR\n", __func__, tm);
  77
  78         return 0;
  79 }
  80
  81 static int ds1672_set_time(struct device *dev, struct rtc_time *tm)
  82 {
  83         struct i2c_client *client = to_i2c_client(dev);
  84         int xfer;
  85         unsigned char buf[6];
  86         unsigned long secs = rtc_tm_to_time64(tm);
  87
  88         buf[0] = DS1672_REG_CNT_BASE;
  89         buf[1] = secs & 0x000000FF;
  90         buf[2] = (secs & 0x0000FF00) >> 8;
  91         buf[3] = (secs & 0x00FF0000) >> 16;
  92         buf[4] = (secs & 0xFF000000) >> 24;
  93         buf[5] = 0;             /* set control reg to enable counting */
  94
  95         xfer = i2c_master_send(client, buf, 6);
  96         if (xfer != 6) {
  97                 dev_err(&client->dev, "%s: send: %d\n", __func__, xfer);
  98                 return -EIO;
  99         }
 100
 101         return 0;
 102 }
 103
 104 static const struct rtc_class_ops ds1672_rtc_ops = {
 105         .read_time = ds1672_read_time,
 106         .set_time = ds1672_set_time,
 107 };
 108
 109 static int ds1672_probe(struct i2c_client *client,
 110                         const struct i2c_device_id *id)
 111 {
 112         int err = 0;
 113         struct rtc_device *rtc;
 114
 115         dev_dbg(&client->dev, "%s\n", __func__);
 116
 117         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 118                 return -ENODEV;
 119
 120         rtc = devm_rtc_allocate_device(&client->dev);
 121         if (IS_ERR(rtc))
 122                 return PTR_ERR(rtc);
 123
 124         rtc->ops = &ds1672_rtc_ops;
 125         rtc->range_max = U32_MAX;
 126
 127         err = devm_rtc_register_device(rtc);
 128         if (err)
 129                 return err;
 130
 131         i2c_set_clientdata(client, rtc);
 132
 133         return 0;
 134 }
 135
 136 static const struct i2c_device_id ds1672_id[] = {
 137         { "ds1672", 0 },
 138         { }
 139 };
 140 MODULE_DEVICE_TABLE(i2c, ds1672_id);
 141
 142 static const struct of_device_id ds1672_of_match[] = {
 143         { .compatible = "dallas,ds1672" },
 144         { }
 145 };
 146 MODULE_DEVICE_TABLE(of, ds1672_of_match);
 147
 148 static struct i2c_driver ds1672_driver = {
 149         .driver = {
 150                    .name = "rtc-ds1672",
 151                    .of_match_table = of_match_ptr(ds1672_of_match),
 152         },
 153         .probe = &ds1672_probe,
 154         .id_table = ds1672_id,
 155 };
 156
 157 module_i2c_driver(ds1672_driver);
 158
 159 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
 160 MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
 161 MODULE_LICENSE("GPL");