rtc: update and use the MAX6900 century byte
[linux-2.6.git] / drivers / rtc / rtc-max6900.c
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 #define DRV_NAME "max6900"
21 #define DRV_VERSION "0.1"
22
23 /*
24  * register indices
25  */
26 #define MAX6900_REG_SC                  0       /* seconds      00-59 */
27 #define MAX6900_REG_MN                  1       /* minutes      00-59 */
28 #define MAX6900_REG_HR                  2       /* hours        00-23 */
29 #define MAX6900_REG_DT                  3       /* day of month 00-31 */
30 #define MAX6900_REG_MO                  4       /* month        01-12 */
31 #define MAX6900_REG_DW                  5       /* day of week   1-7  */
32 #define MAX6900_REG_YR                  6       /* year         00-99 */
33 #define MAX6900_REG_CT                  7       /* control */
34                                                 /* register 8 is undocumented */
35 #define MAX6900_REG_CENTURY             9       /* century */
36 #define MAX6900_REG_LEN                 10
37
38 #define MAX6900_BURST_LEN               8       /* can burst r/w first 8 regs */
39
40 #define MAX6900_REG_CT_WP               (1 << 7)        /* Write Protect */
41
42
43 /*
44  * register read/write commands
45  */
46 #define MAX6900_REG_CONTROL_WRITE       0x8e
47 #define MAX6900_REG_CENTURY_WRITE       0x92
48 #define MAX6900_REG_CENTURY_READ        0x93
49 #define MAX6900_REG_RESERVED_READ       0x96
50 #define MAX6900_REG_BURST_WRITE         0xbe
51 #define MAX6900_REG_BURST_READ          0xbf
52
53 #define MAX6900_IDLE_TIME_AFTER_WRITE   3       /* specification says 2.5 mS */
54
55 #define MAX6900_I2C_ADDR                0xa0
56
57 static unsigned short normal_i2c[] = {
58         MAX6900_I2C_ADDR >> 1,
59         I2C_CLIENT_END
60 };
61
62 I2C_CLIENT_INSMOD;                      /* defines addr_data */
63
64 static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind);
65
66 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
67 {
68         u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
69         u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
70         struct i2c_msg msgs[4] = {
71                 {
72                         .addr   = client->addr,
73                         .flags  = 0, /* write */
74                         .len    = sizeof(reg_burst_read),
75                         .buf    = reg_burst_read
76                 },
77                 {
78                         .addr   = client->addr,
79                         .flags  = I2C_M_RD,
80                         .len    = MAX6900_BURST_LEN,
81                         .buf    = buf
82                 },
83                 {
84                         .addr   = client->addr,
85                         .flags  = 0, /* write */
86                         .len    = sizeof(reg_century_read),
87                         .buf    = reg_century_read
88                 },
89                 {
90                         .addr   = client->addr,
91                         .flags  = I2C_M_RD,
92                         .len    = sizeof(buf[MAX6900_REG_CENTURY]),
93                         .buf    = &buf[MAX6900_REG_CENTURY]
94                 }
95         };
96         int rc;
97
98         rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
99         if (rc != ARRAY_SIZE(msgs)) {
100                 dev_err(&client->dev, "%s: register read failed\n",
101                         __FUNCTION__);
102                 return -EIO;
103         }
104         return 0;
105 }
106
107 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
108 {
109         u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
110         struct i2c_msg century_msgs[1] = {
111                 {
112                         .addr   = client->addr,
113                         .flags  = 0, /* write */
114                         .len    = sizeof(i2c_century_buf),
115                         .buf    = i2c_century_buf
116                 }
117         };
118         u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
119         struct i2c_msg burst_msgs[1] = {
120                 {
121                         .addr   = client->addr,
122                         .flags  = 0, /* write */
123                         .len    = sizeof(i2c_burst_buf),
124                         .buf    = i2c_burst_buf
125                 }
126         };
127         int rc;
128
129         /*
130          * We have to make separate calls to i2c_transfer because of
131          * the need to delay after each write to the chip.  Also,
132          * we write the century byte first, since we set the write-protect
133          * bit as part of the burst write.
134          */
135         i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
136         rc = i2c_transfer(client->adapter, century_msgs,
137                           ARRAY_SIZE(century_msgs));
138         if (rc != ARRAY_SIZE(century_msgs))
139                 goto write_failed;
140         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
141
142         memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
143
144         rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
145         if (rc != ARRAY_SIZE(burst_msgs))
146                 goto write_failed;
147         msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
148
149         return 0;
150
151 write_failed:
152         dev_err(&client->dev, "%s: register write failed\n",
153                 __FUNCTION__);
154         return -EIO;
155 }
156
157 static int max6900_i2c_validate_client(struct i2c_client *client)
158 {
159         u8 regs[MAX6900_REG_LEN];
160         u8 zero_mask[] = {
161                 0x80,   /* seconds */
162                 0x80,   /* minutes */
163                 0x40,   /* hours */
164                 0xc0,   /* day of month */
165                 0xe0,   /* month */
166                 0xf8,   /* day of week */
167                 0x00,   /* year */
168                 0x7f,   /* control */
169         };
170         int i;
171         int rc;
172         int reserved;
173
174         reserved = i2c_smbus_read_byte_data(client, MAX6900_REG_RESERVED_READ);
175         if (reserved != 0x07)
176                 return -ENODEV;
177
178         rc = max6900_i2c_read_regs(client, regs);
179         if (rc < 0)
180                 return rc;
181
182         for (i = 0; i < ARRAY_SIZE(zero_mask); ++i) {
183                 if (regs[i] & zero_mask[i])
184                         return -ENODEV;
185         }
186
187         return 0;
188 }
189
190 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
191 {
192         int rc;
193         u8 regs[MAX6900_REG_LEN];
194
195         rc = max6900_i2c_read_regs(client, regs);
196         if (rc < 0)
197                 return rc;
198
199         tm->tm_sec = BCD2BIN(regs[MAX6900_REG_SC]);
200         tm->tm_min = BCD2BIN(regs[MAX6900_REG_MN]);
201         tm->tm_hour = BCD2BIN(regs[MAX6900_REG_HR] & 0x3f);
202         tm->tm_mday = BCD2BIN(regs[MAX6900_REG_DT]);
203         tm->tm_mon = BCD2BIN(regs[MAX6900_REG_MO]) - 1;
204         tm->tm_year = BCD2BIN(regs[MAX6900_REG_YR]) +
205                       BCD2BIN(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
206         tm->tm_wday = BCD2BIN(regs[MAX6900_REG_DW]);
207
208         return 0;
209 }
210
211 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
212 {
213         int rc;
214         rc = i2c_smbus_write_byte_data (client, MAX6900_REG_CONTROL_WRITE, 0);
215         if (rc < 0) {
216                 dev_err(&client->dev, "%s: control register write failed\n",
217                         __FUNCTION__);
218                 return -EIO;
219         }
220         return 0;
221 }
222
223 static int max6900_i2c_set_time(struct i2c_client *client,
224                                 struct rtc_time const *tm)
225 {
226         u8 regs[MAX6900_REG_LEN];
227         int rc;
228
229         rc = max6900_i2c_clear_write_protect(client);
230         if (rc < 0)
231                 return rc;
232
233         regs[MAX6900_REG_SC] = BIN2BCD(tm->tm_sec);
234         regs[MAX6900_REG_MN] = BIN2BCD(tm->tm_min);
235         regs[MAX6900_REG_HR] = BIN2BCD(tm->tm_hour);
236         regs[MAX6900_REG_DT] = BIN2BCD(tm->tm_mday);
237         regs[MAX6900_REG_MO] = BIN2BCD(tm->tm_mon + 1);
238         regs[MAX6900_REG_DW] = BIN2BCD(tm->tm_wday);
239         regs[MAX6900_REG_YR] = BIN2BCD(tm->tm_year % 100);
240         regs[MAX6900_REG_CENTURY] = BIN2BCD((tm->tm_year + 1900) / 100);
241         /* set write protect */
242         regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
243
244         rc = max6900_i2c_write_regs(client, regs);
245         if (rc < 0)
246                 return rc;
247
248         return 0;
249 }
250
251 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
252 {
253         return max6900_i2c_read_time(to_i2c_client(dev), tm);
254 }
255
256 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
257 {
258         return max6900_i2c_set_time(to_i2c_client(dev), tm);
259 }
260
261 static int max6900_attach_adapter(struct i2c_adapter *adapter)
262 {
263         return i2c_probe(adapter, &addr_data, max6900_probe);
264 }
265
266 static int max6900_detach_client(struct i2c_client *client)
267 {
268         struct rtc_device *const rtc = i2c_get_clientdata(client);
269
270         if (rtc)
271                 rtc_device_unregister(rtc);
272
273         return i2c_detach_client(client);
274 }
275
276 static struct i2c_driver max6900_driver = {
277         .driver         = {
278                 .name   = DRV_NAME,
279         },
280         .id             = I2C_DRIVERID_MAX6900,
281         .attach_adapter = max6900_attach_adapter,
282         .detach_client  = max6900_detach_client,
283 };
284
285 static const struct rtc_class_ops max6900_rtc_ops = {
286         .read_time      = max6900_rtc_read_time,
287         .set_time       = max6900_rtc_set_time,
288 };
289
290 static int max6900_probe(struct i2c_adapter *adapter, int addr, int kind)
291 {
292         int rc = 0;
293         struct i2c_client *client = NULL;
294         struct rtc_device *rtc = NULL;
295
296         if (!i2c_check_functionality(adapter, I2C_FUNC_I2C)) {
297                 rc = -ENODEV;
298                 goto failout;
299         }
300
301         client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
302         if (client == NULL) {
303                 rc = -ENOMEM;
304                 goto failout;
305         }
306
307         client->addr = addr;
308         client->adapter = adapter;
309         client->driver = &max6900_driver;
310         strlcpy(client->name, DRV_NAME, I2C_NAME_SIZE);
311
312         if (kind < 0) {
313                 rc = max6900_i2c_validate_client(client);
314                 if (rc < 0)
315                         goto failout;
316         }
317
318         rc = i2c_attach_client(client);
319         if (rc < 0)
320                 goto failout;
321
322         dev_info(&client->dev,
323                  "chip found, driver version " DRV_VERSION "\n");
324
325         rtc = rtc_device_register(max6900_driver.driver.name,
326                                   &client->dev,
327                                   &max6900_rtc_ops, THIS_MODULE);
328         if (IS_ERR(rtc)) {
329                 rc = PTR_ERR(rtc);
330                 goto failout_detach;
331         }
332
333         i2c_set_clientdata(client, rtc);
334
335         return 0;
336
337 failout_detach:
338         i2c_detach_client(client);
339 failout:
340         kfree(client);
341         return rc;
342 }
343
344 static int __init max6900_init(void)
345 {
346         return i2c_add_driver(&max6900_driver);
347 }
348
349 static void __exit max6900_exit(void)
350 {
351         i2c_del_driver(&max6900_driver);
352 }
353
354 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
355 MODULE_LICENSE("GPL");
356 MODULE_VERSION(DRV_VERSION);
357
358 module_init(max6900_init);
359 module_exit(max6900_exit);