1 /*
2 * rtc class driver for the Maxim MAX6900 chip
3 *
4 * Author: Dale Farnsworth <dale@farnsworth.org>
5 *
6 * based on previously existing rtc class drivers
7 *
8 * 2007 (c) MontaVista, Software, Inc. This file is licensed under
9 * the terms of the GNU General Public License version 2. This program
10 * is licensed "as is" without any warranty of any kind, whether express
11 * or implied.
12 */
13
14 #include <linux/module.h>
15 #include <linux/i2c.h>
16 #include <linux/bcd.h>
17 #include <linux/rtc.h>
18 #include <linux/delay.h>
19
20 /*
21 * register indices
22 */
23 #define MAX6900_REG_SC 0 /* seconds 00-59 */
24 #define MAX6900_REG_MN 1 /* minutes 00-59 */
25 #define MAX6900_REG_HR 2 /* hours 00-23 */
26 #define MAX6900_REG_DT 3 /* day of month 00-31 */
27 #define MAX6900_REG_MO 4 /* month 01-12 */
28 #define MAX6900_REG_DW 5 /* day of week 1-7 */
29 #define MAX6900_REG_YR 6 /* year 00-99 */
30 #define MAX6900_REG_CT 7 /* control */
31 /* register 8 is undocumented */
32 #define MAX6900_REG_CENTURY 9 /* century */
33 #define MAX6900_REG_LEN 10
34
35 #define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */
36
37 #define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */
38
39 /*
40 * register read/write commands
41 */
42 #define MAX6900_REG_CONTROL_WRITE 0x8e
43 #define MAX6900_REG_CENTURY_WRITE 0x92
44 #define MAX6900_REG_CENTURY_READ 0x93
45 #define MAX6900_REG_RESERVED_READ 0x96
46 #define MAX6900_REG_BURST_WRITE 0xbe
47 #define MAX6900_REG_BURST_READ 0xbf
48
49 #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */
50
51 static struct i2c_driver max6900_driver;
52
max6900_i2c_read_regs(struct i2c_client * client,u8 * buf)53 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
54 {
55 u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
56 u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
57 struct i2c_msg msgs[4] = {
58 {
59 .addr = client->addr,
60 .flags = 0, /* write */
61 .len = sizeof(reg_burst_read),
62 .buf = reg_burst_read}
63 ,
64 {
65 .addr = client->addr,
66 .flags = I2C_M_RD,
67 .len = MAX6900_BURST_LEN,
68 .buf = buf}
69 ,
70 {
71 .addr = client->addr,
72 .flags = 0, /* write */
73 .len = sizeof(reg_century_read),
74 .buf = reg_century_read}
75 ,
76 {
77 .addr = client->addr,
78 .flags = I2C_M_RD,
79 .len = sizeof(buf[MAX6900_REG_CENTURY]),
80 .buf = &buf[MAX6900_REG_CENTURY]
81 }
82 };
83 int rc;
84
85 rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
86 if (rc != ARRAY_SIZE(msgs)) {
87 dev_err(&client->dev, "%s: register read failed\n", __func__);
88 return -EIO;
89 }
90 return 0;
91 }
92
max6900_i2c_write_regs(struct i2c_client * client,u8 const * buf)93 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
94 {
95 u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
96 struct i2c_msg century_msgs[1] = {
97 {
98 .addr = client->addr,
99 .flags = 0, /* write */
100 .len = sizeof(i2c_century_buf),
101 .buf = i2c_century_buf}
102 };
103 u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
104 struct i2c_msg burst_msgs[1] = {
105 {
106 .addr = client->addr,
107 .flags = 0, /* write */
108 .len = sizeof(i2c_burst_buf),
109 .buf = i2c_burst_buf}
110 };
111 int rc;
112
113 /*
114 * We have to make separate calls to i2c_transfer because of
115 * the need to delay after each write to the chip. Also,
116 * we write the century byte first, since we set the write-protect
117 * bit as part of the burst write.
118 */
119 i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
120
121 rc = i2c_transfer(client->adapter, century_msgs,
122 ARRAY_SIZE(century_msgs));
123 if (rc != ARRAY_SIZE(century_msgs))
124 goto write_failed;
125
126 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
127
128 memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
129
130 rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
131 if (rc != ARRAY_SIZE(burst_msgs))
132 goto write_failed;
133 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
134
135 return 0;
136
137 write_failed:
138 dev_err(&client->dev, "%s: register write failed\n", __func__);
139 return -EIO;
140 }
141
max6900_i2c_read_time(struct i2c_client * client,struct rtc_time * tm)142 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
143 {
144 int rc;
145 u8 regs[MAX6900_REG_LEN];
146
147 rc = max6900_i2c_read_regs(client, regs);
148 if (rc < 0)
149 return rc;
150
151 tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
152 tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
153 tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
154 tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
155 tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
156 tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
157 bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
158 tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
159
160 return rtc_valid_tm(tm);
161 }
162
max6900_i2c_clear_write_protect(struct i2c_client * client)163 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
164 {
165 return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
166 }
167
168 static int
max6900_i2c_set_time(struct i2c_client * client,struct rtc_time const * tm)169 max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
170 {
171 u8 regs[MAX6900_REG_LEN];
172 int rc;
173
174 rc = max6900_i2c_clear_write_protect(client);
175 if (rc < 0)
176 return rc;
177
178 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
179 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
180 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
181 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
182 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
183 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
184 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
185 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
186 /* set write protect */
187 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
188
189 rc = max6900_i2c_write_regs(client, regs);
190 if (rc < 0)
191 return rc;
192
193 return 0;
194 }
195
max6900_rtc_read_time(struct device * dev,struct rtc_time * tm)196 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
197 {
198 return max6900_i2c_read_time(to_i2c_client(dev), tm);
199 }
200
max6900_rtc_set_time(struct device * dev,struct rtc_time * tm)201 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
202 {
203 return max6900_i2c_set_time(to_i2c_client(dev), tm);
204 }
205
206 static const struct rtc_class_ops max6900_rtc_ops = {
207 .read_time = max6900_rtc_read_time,
208 .set_time = max6900_rtc_set_time,
209 };
210
211 static int
max6900_probe(struct i2c_client * client,const struct i2c_device_id * id)212 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
213 {
214 struct rtc_device *rtc;
215
216 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
217 return -ENODEV;
218
219 rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
220 &max6900_rtc_ops, THIS_MODULE);
221 if (IS_ERR(rtc))
222 return PTR_ERR(rtc);
223
224 i2c_set_clientdata(client, rtc);
225
226 return 0;
227 }
228
229 static struct i2c_device_id max6900_id[] = {
230 { "max6900", 0 },
231 { }
232 };
233 MODULE_DEVICE_TABLE(i2c, max6900_id);
234
235 static struct i2c_driver max6900_driver = {
236 .driver = {
237 .name = "rtc-max6900",
238 },
239 .probe = max6900_probe,
240 .id_table = max6900_id,
241 };
242
243 module_i2c_driver(max6900_driver);
244
245 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
246 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
247 MODULE_LICENSE("GPL");
248