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