WorkStruct: make allyesconfig
[linux-3.10.git] / 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 #include <linux/mutex.h>
30 #include <linux/workqueue.h>
31
32 #define DS1374_REG_TOD0         0x00
33 #define DS1374_REG_TOD1         0x01
34 #define DS1374_REG_TOD2         0x02
35 #define DS1374_REG_TOD3         0x03
36 #define DS1374_REG_WDALM0       0x04
37 #define DS1374_REG_WDALM1       0x05
38 #define DS1374_REG_WDALM2       0x06
39 #define DS1374_REG_CR           0x07
40 #define DS1374_REG_SR           0x08
41 #define DS1374_REG_SR_OSF       0x80
42 #define DS1374_REG_TCR          0x09
43
44 #define DS1374_DRV_NAME         "ds1374"
45
46 static DEFINE_MUTEX(ds1374_mutex);
47
48 static struct i2c_driver ds1374_driver;
49 static struct i2c_client *save_client;
50
51 static unsigned short ignore[] = { I2C_CLIENT_END };
52 static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
53
54 static struct i2c_client_address_data addr_data = {
55         .normal_i2c = normal_addr,
56         .probe = ignore,
57         .ignore = ignore,
58 };
59
60 static ulong ds1374_read_rtc(void)
61 {
62         ulong time = 0;
63         int reg = DS1374_REG_WDALM0;
64
65         while (reg--) {
66                 s32 tmp;
67                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
68                         dev_warn(&save_client->dev,
69                                  "can't read from rtc chip\n");
70                         return 0;
71                 }
72                 time = (time << 8) | (tmp & 0xff);
73         }
74         return time;
75 }
76
77 static void ds1374_write_rtc(ulong time)
78 {
79         int reg;
80
81         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
82                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
83                     < 0) {
84                         dev_warn(&save_client->dev,
85                                  "can't write to rtc chip\n");
86                         break;
87                 }
88                 time = time >> 8;
89         }
90 }
91
92 static void ds1374_check_rtc_status(void)
93 {
94         s32 tmp;
95
96         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
97         if (tmp < 0) {
98                 dev_warn(&save_client->dev,
99                          "can't read status from rtc chip\n");
100                 return;
101         }
102         if (tmp & DS1374_REG_SR_OSF) {
103                 dev_warn(&save_client->dev,
104                          "oscillator discontinuity flagged, time unreliable\n");
105                 tmp &= ~DS1374_REG_SR_OSF;
106                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
107                                                 tmp & 0xff);
108                 if (tmp < 0)
109                         dev_warn(&save_client->dev,
110                                  "can't clear discontinuity notification\n");
111         }
112 }
113
114 ulong ds1374_get_rtc_time(void)
115 {
116         ulong t1, t2;
117         int limit = 10;         /* arbitrary retry limit */
118
119         mutex_lock(&ds1374_mutex);
120
121         /*
122          * Since the reads are being performed one byte at a time using
123          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
124          * carry will occur during the read. To detect this, 2 reads are
125          * performed and compared.
126          */
127         do {
128                 t1 = ds1374_read_rtc();
129                 t2 = ds1374_read_rtc();
130         } while (t1 != t2 && limit--);
131
132         mutex_unlock(&ds1374_mutex);
133
134         if (t1 != t2) {
135                 dev_warn(&save_client->dev,
136                          "can't get consistent time from rtc chip\n");
137                 t1 = 0;
138         }
139
140         return t1;
141 }
142
143 static ulong new_time;
144
145 static void ds1374_set_work(struct work_struct *work)
146 {
147         ulong t1, t2;
148         int limit = 10;         /* arbitrary retry limit */
149
150         t1 = new_time;
151
152         mutex_lock(&ds1374_mutex);
153
154         /*
155          * Since the writes are being performed one byte at a time using
156          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
157          * carry will occur during the write. To detect this, the write
158          * value is read back and compared.
159          */
160         do {
161                 ds1374_write_rtc(t1);
162                 t2 = ds1374_read_rtc();
163         } while (t1 != t2 && limit--);
164
165         mutex_unlock(&ds1374_mutex);
166
167         if (t1 != t2)
168                 dev_warn(&save_client->dev,
169                          "can't confirm time set from rtc chip\n");
170 }
171
172 static struct workqueue_struct *ds1374_workqueue;
173
174 static DECLARE_WORK(ds1374_work, ds1374_set_work);
175
176 int ds1374_set_rtc_time(ulong nowtime)
177 {
178         new_time = nowtime;
179
180         if (in_interrupt())
181                 queue_work(ds1374_workqueue, &ds1374_work);
182         else
183                 ds1374_set_work(NULL);
184
185         return 0;
186 }
187
188 /*
189  *****************************************************************************
190  *
191  *      Driver Interface
192  *
193  *****************************************************************************
194  */
195 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
196 {
197         struct i2c_client *client;
198         int rc;
199
200         client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
201         if (!client)
202                 return -ENOMEM;
203
204         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
205         client->addr = addr;
206         client->adapter = adap;
207         client->driver = &ds1374_driver;
208
209         ds1374_workqueue = create_singlethread_workqueue("ds1374");
210
211         if ((rc = i2c_attach_client(client)) != 0) {
212                 kfree(client);
213                 return rc;
214         }
215
216         save_client = client;
217
218         ds1374_check_rtc_status();
219
220         return 0;
221 }
222
223 static int ds1374_attach(struct i2c_adapter *adap)
224 {
225         return i2c_probe(adap, &addr_data, ds1374_probe);
226 }
227
228 static int ds1374_detach(struct i2c_client *client)
229 {
230         int rc;
231
232         if ((rc = i2c_detach_client(client)) == 0) {
233                 kfree(i2c_get_clientdata(client));
234                 destroy_workqueue(ds1374_workqueue);
235         }
236         return rc;
237 }
238
239 static struct i2c_driver ds1374_driver = {
240         .driver = {
241                 .name   = DS1374_DRV_NAME,
242         },
243         .id = I2C_DRIVERID_DS1374,
244         .attach_adapter = ds1374_attach,
245         .detach_client = ds1374_detach,
246 };
247
248 static int __init ds1374_init(void)
249 {
250         return i2c_add_driver(&ds1374_driver);
251 }
252
253 static void __exit ds1374_exit(void)
254 {
255         i2c_del_driver(&ds1374_driver);
256 }
257
258 module_init(ds1374_init);
259 module_exit(ds1374_exit);
260
261 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
262 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
263 MODULE_LICENSE("GPL");