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