Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq
[linux-2.6] / drivers / i2c / chips / ds1374.c
1 /*
2  * drivers/i2c/chips/ds1374.c
3  *
4  * I2C client/driver for the Maxim/Dallas DS1374 Real-Time Clock
5  *
6  * Author: Randy Vinson <rvinson@mvista.com>
7  *
8  * Based on the m41t00.c by Mark Greer <mgreer@mvista.com>
9  *
10  * 2005 (c) MontaVista Software, Inc. This file is licensed under
11  * the terms of the GNU General Public License version 2. This program
12  * is licensed "as is" without any warranty of any kind, whether express
13  * or implied.
14  */
15 /*
16  * This i2c client/driver wedges between the drivers/char/genrtc.c RTC
17  * interface and the SMBus interface of the i2c subsystem.
18  * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
19  * recommened in .../Documentation/i2c/writing-clients section
20  * "Sending and receiving", using SMBus level communication is preferred.
21  */
22
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/interrupt.h>
26 #include <linux/i2c.h>
27 #include <linux/rtc.h>
28 #include <linux/bcd.h>
29
30 #define DS1374_REG_TOD0         0x00
31 #define DS1374_REG_TOD1         0x01
32 #define DS1374_REG_TOD2         0x02
33 #define DS1374_REG_TOD3         0x03
34 #define DS1374_REG_WDALM0       0x04
35 #define DS1374_REG_WDALM1       0x05
36 #define DS1374_REG_WDALM2       0x06
37 #define DS1374_REG_CR           0x07
38 #define DS1374_REG_SR           0x08
39 #define DS1374_REG_SR_OSF       0x80
40 #define DS1374_REG_TCR          0x09
41
42 #define DS1374_DRV_NAME         "ds1374"
43
44 static DECLARE_MUTEX(ds1374_mutex);
45
46 static struct i2c_driver ds1374_driver;
47 static struct i2c_client *save_client;
48
49 static unsigned short ignore[] = { I2C_CLIENT_END };
50 static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
51
52 static struct i2c_client_address_data addr_data = {
53         .normal_i2c = normal_addr,
54         .probe = ignore,
55         .ignore = ignore,
56 };
57
58 static ulong ds1374_read_rtc(void)
59 {
60         ulong time = 0;
61         int reg = DS1374_REG_WDALM0;
62
63         while (reg--) {
64                 s32 tmp;
65                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
66                         dev_warn(&save_client->dev,
67                                  "can't read from rtc chip\n");
68                         return 0;
69                 }
70                 time = (time << 8) | (tmp & 0xff);
71         }
72         return time;
73 }
74
75 static void ds1374_write_rtc(ulong time)
76 {
77         int reg;
78
79         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
80                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
81                     < 0) {
82                         dev_warn(&save_client->dev,
83                                  "can't write to rtc chip\n");
84                         break;
85                 }
86                 time = time >> 8;
87         }
88 }
89
90 static void ds1374_check_rtc_status(void)
91 {
92         s32 tmp;
93
94         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
95         if (tmp < 0) {
96                 dev_warn(&save_client->dev,
97                          "can't read status from rtc chip\n");
98                 return;
99         }
100         if (tmp & DS1374_REG_SR_OSF) {
101                 dev_warn(&save_client->dev,
102                          "oscillator discontinuity flagged, time unreliable\n");
103                 tmp &= ~DS1374_REG_SR_OSF;
104                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
105                                                 tmp & 0xff);
106                 if (tmp < 0)
107                         dev_warn(&save_client->dev,
108                                  "can't clear discontinuity notification\n");
109         }
110 }
111
112 ulong ds1374_get_rtc_time(void)
113 {
114         ulong t1, t2;
115         int limit = 10;         /* arbitrary retry limit */
116
117         down(&ds1374_mutex);
118
119         /*
120          * Since the reads are being performed one byte at a time using
121          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
122          * carry will occur during the read. To detect this, 2 reads are
123          * performed and compared.
124          */
125         do {
126                 t1 = ds1374_read_rtc();
127                 t2 = ds1374_read_rtc();
128         } while (t1 != t2 && limit--);
129
130         up(&ds1374_mutex);
131
132         if (t1 != t2) {
133                 dev_warn(&save_client->dev,
134                          "can't get consistent time from rtc chip\n");
135                 t1 = 0;
136         }
137
138         return t1;
139 }
140
141 static void ds1374_set_tlet(ulong arg)
142 {
143         ulong t1, t2;
144         int limit = 10;         /* arbitrary retry limit */
145
146         t1 = *(ulong *) arg;
147
148         down(&ds1374_mutex);
149
150         /*
151          * Since the writes are being performed one byte at a time using
152          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
153          * carry will occur during the write. To detect this, the write
154          * value is read back and compared.
155          */
156         do {
157                 ds1374_write_rtc(t1);
158                 t2 = ds1374_read_rtc();
159         } while (t1 != t2 && limit--);
160
161         up(&ds1374_mutex);
162
163         if (t1 != t2)
164                 dev_warn(&save_client->dev,
165                          "can't confirm time set from rtc chip\n");
166 }
167
168 static ulong new_time;
169
170 DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet, (ulong) & new_time);
171
172 int ds1374_set_rtc_time(ulong nowtime)
173 {
174         new_time = nowtime;
175
176         if (in_interrupt())
177                 tasklet_schedule(&ds1374_tasklet);
178         else
179                 ds1374_set_tlet((ulong) & new_time);
180
181         return 0;
182 }
183
184 /*
185  *****************************************************************************
186  *
187  *      Driver Interface
188  *
189  *****************************************************************************
190  */
191 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
192 {
193         struct i2c_client *client;
194         int rc;
195
196         client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL);
197         if (!client)
198                 return -ENOMEM;
199
200         memset(client, 0, sizeof(struct i2c_client));
201         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
202         client->flags = I2C_DF_NOTIFY;
203         client->addr = addr;
204         client->adapter = adap;
205         client->driver = &ds1374_driver;
206
207         if ((rc = i2c_attach_client(client)) != 0) {
208                 kfree(client);
209                 return rc;
210         }
211
212         save_client = client;
213
214         ds1374_check_rtc_status();
215
216         return 0;
217 }
218
219 static int ds1374_attach(struct i2c_adapter *adap)
220 {
221         return i2c_probe(adap, &addr_data, ds1374_probe);
222 }
223
224 static int ds1374_detach(struct i2c_client *client)
225 {
226         int rc;
227
228         if ((rc = i2c_detach_client(client)) == 0) {
229                 kfree(i2c_get_clientdata(client));
230                 tasklet_kill(&ds1374_tasklet);
231         }
232         return rc;
233 }
234
235 static struct i2c_driver ds1374_driver = {
236         .owner = THIS_MODULE,
237         .name = DS1374_DRV_NAME,
238         .id = I2C_DRIVERID_DS1374,
239         .flags = I2C_DF_NOTIFY,
240         .attach_adapter = ds1374_attach,
241         .detach_client = ds1374_detach,
242 };
243
244 static int __init ds1374_init(void)
245 {
246         return i2c_add_driver(&ds1374_driver);
247 }
248
249 static void __exit ds1374_exit(void)
250 {
251         i2c_del_driver(&ds1374_driver);
252 }
253
254 module_init(ds1374_init);
255 module_exit(ds1374_exit);
256
257 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
258 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
259 MODULE_LICENSE("GPL");