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 */
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	{ "ds1672", 0 },
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 <a.zummo@towertech.it>");
159MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
160MODULE_LICENSE("GPL");
161