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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 <[email protected]>
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 */
26static 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
81static 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
104static const struct rtc_class_ops ds1672_rtc_ops = {
105 .read_time = ds1672_read_time,
106 .set_time = ds1672_set_time,
107};
108
109static int ds1672_probe(struct i2c_client *client)
110{
111 int err = 0;
112 struct rtc_device *rtc;
113
114 dev_dbg(&client->dev, "%s\n", __func__);
115
116 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
117 return -ENODEV;
118
119 rtc = devm_rtc_allocate_device(&client->dev);
120 if (IS_ERR(rtc))
121 return PTR_ERR(rtc);
122
123 rtc->ops = &ds1672_rtc_ops;
124 rtc->range_max = U32_MAX;
125
126 err = devm_rtc_register_device(rtc);
127 if (err)
128 return err;
129
130 i2c_set_clientdata(client, rtc);
131
132 return 0;
133}
134
135static const struct i2c_device_id ds1672_id[] = {
136 { .name = "ds1672" },
137 { }
138};
139MODULE_DEVICE_TABLE(i2c, ds1672_id);
140
141static const __maybe_unused struct of_device_id ds1672_of_match[] = {
142 { .compatible = "dallas,ds1672" },
143 { }
144};
145MODULE_DEVICE_TABLE(of, ds1672_of_match);
146
147static struct i2c_driver ds1672_driver = {
148 .driver = {
149 .name = "rtc-ds1672",
150 .of_match_table = of_match_ptr(ds1672_of_match),
151 },
152 .probe = ds1672_probe,
153 .id_table = ds1672_id,
154};
155
156module_i2c_driver(ds1672_driver);
157
158MODULE_AUTHOR("Alessandro Zummo <[email protected]>");
159MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
160MODULE_LICENSE("GPL");