xref: /linux/drivers/rtc/rtc-ds1672.c (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
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  */
ds1672_read_time(struct device * dev,struct rtc_time * tm)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 
ds1672_set_time(struct device * dev,struct rtc_time * tm)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 
ds1672_probe(struct i2c_client * client)109 static 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 
135 static const struct i2c_device_id ds1672_id[] = {
136 	{ "ds1672" },
137 	{ }
138 };
139 MODULE_DEVICE_TABLE(i2c, ds1672_id);
140 
141 static const __maybe_unused struct of_device_id ds1672_of_match[] = {
142 	{ .compatible = "dallas,ds1672" },
143 	{ }
144 };
145 MODULE_DEVICE_TABLE(of, ds1672_of_match);
146 
147 static 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 
156 module_i2c_driver(ds1672_driver);
157 
158 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
159 MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
160 MODULE_LICENSE("GPL");
161