Merge master.kernel.org:/pub/scm/linux/kernel/git/gregkh/i2c-2.6
[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         .force = ignore,
57 };
58
59 static ulong ds1374_read_rtc(void)
60 {
61         ulong time = 0;
62         int reg = DS1374_REG_WDALM0;
63
64         while (reg--) {
65                 s32 tmp;
66                 if ((tmp = i2c_smbus_read_byte_data(save_client, reg)) < 0) {
67                         dev_warn(&save_client->dev,
68                                  "can't read from rtc chip\n");
69                         return 0;
70                 }
71                 time = (time << 8) | (tmp & 0xff);
72         }
73         return time;
74 }
75
76 static void ds1374_write_rtc(ulong time)
77 {
78         int reg;
79
80         for (reg = DS1374_REG_TOD0; reg < DS1374_REG_WDALM0; reg++) {
81                 if (i2c_smbus_write_byte_data(save_client, reg, time & 0xff)
82                     < 0) {
83                         dev_warn(&save_client->dev,
84                                  "can't write to rtc chip\n");
85                         break;
86                 }
87                 time = time >> 8;
88         }
89 }
90
91 static void ds1374_check_rtc_status(void)
92 {
93         s32 tmp;
94
95         tmp = i2c_smbus_read_byte_data(save_client, DS1374_REG_SR);
96         if (tmp < 0) {
97                 dev_warn(&save_client->dev,
98                          "can't read status from rtc chip\n");
99                 return;
100         }
101         if (tmp & DS1374_REG_SR_OSF) {
102                 dev_warn(&save_client->dev,
103                          "oscillator discontinuity flagged, time unreliable\n");
104                 tmp &= ~DS1374_REG_SR_OSF;
105                 tmp = i2c_smbus_write_byte_data(save_client, DS1374_REG_SR,
106                                                 tmp & 0xff);
107                 if (tmp < 0)
108                         dev_warn(&save_client->dev,
109                                  "can't clear discontinuity notification\n");
110         }
111 }
112
113 ulong ds1374_get_rtc_time(void)
114 {
115         ulong t1, t2;
116         int limit = 10;         /* arbitrary retry limit */
117
118         down(&ds1374_mutex);
119
120         /*
121          * Since the reads are being performed one byte at a time using
122          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
123          * carry will occur during the read. To detect this, 2 reads are
124          * performed and compared.
125          */
126         do {
127                 t1 = ds1374_read_rtc();
128                 t2 = ds1374_read_rtc();
129         } while (t1 != t2 && limit--);
130
131         up(&ds1374_mutex);
132
133         if (t1 != t2) {
134                 dev_warn(&save_client->dev,
135                          "can't get consistent time from rtc chip\n");
136                 t1 = 0;
137         }
138
139         return t1;
140 }
141
142 static void ds1374_set_tlet(ulong arg)
143 {
144         ulong t1, t2;
145         int limit = 10;         /* arbitrary retry limit */
146
147         t1 = *(ulong *) arg;
148
149         down(&ds1374_mutex);
150
151         /*
152          * Since the writes are being performed one byte at a time using
153          * the SMBus vs a 4-byte i2c transfer, there is a chance that a
154          * carry will occur during the write. To detect this, the write
155          * value is read back and compared.
156          */
157         do {
158                 ds1374_write_rtc(t1);
159                 t2 = ds1374_read_rtc();
160         } while (t1 != t2 && limit--);
161
162         up(&ds1374_mutex);
163
164         if (t1 != t2)
165                 dev_warn(&save_client->dev,
166                          "can't confirm time set from rtc chip\n");
167 }
168
169 ulong new_time;
170
171 DECLARE_TASKLET_DISABLED(ds1374_tasklet, ds1374_set_tlet, (ulong) & new_time);
172
173 int ds1374_set_rtc_time(ulong nowtime)
174 {
175         new_time = nowtime;
176
177         if (in_interrupt())
178                 tasklet_schedule(&ds1374_tasklet);
179         else
180                 ds1374_set_tlet((ulong) & new_time);
181
182         return 0;
183 }
184
185 /*
186  *****************************************************************************
187  *
188  *      Driver Interface
189  *
190  *****************************************************************************
191  */
192 static int ds1374_probe(struct i2c_adapter *adap, int addr, int kind)
193 {
194         struct i2c_client *client;
195         int rc;
196
197         client = kmalloc(sizeof(struct i2c_client), GFP_KERNEL);
198         if (!client)
199                 return -ENOMEM;
200
201         memset(client, 0, sizeof(struct i2c_client));
202         strncpy(client->name, DS1374_DRV_NAME, I2C_NAME_SIZE);
203         client->flags = I2C_DF_NOTIFY;
204         client->addr = addr;
205         client->adapter = adap;
206         client->driver = &ds1374_driver;
207
208         if ((rc = i2c_attach_client(client)) != 0) {
209                 kfree(client);
210                 return rc;
211         }
212
213         save_client = client;
214
215         ds1374_check_rtc_status();
216
217         return 0;
218 }
219
220 static int ds1374_attach(struct i2c_adapter *adap)
221 {
222         return i2c_probe(adap, &addr_data, ds1374_probe);
223 }
224
225 static int ds1374_detach(struct i2c_client *client)
226 {
227         int rc;
228
229         if ((rc = i2c_detach_client(client)) == 0) {
230                 kfree(i2c_get_clientdata(client));
231                 tasklet_kill(&ds1374_tasklet);
232         }
233         return rc;
234 }
235
236 static struct i2c_driver ds1374_driver = {
237         .owner = THIS_MODULE,
238         .name = DS1374_DRV_NAME,
239         .id = I2C_DRIVERID_DS1374,
240         .flags = I2C_DF_NOTIFY,
241         .attach_adapter = ds1374_attach,
242         .detach_client = ds1374_detach,
243 };
244
245 static int __init ds1374_init(void)
246 {
247         return i2c_add_driver(&ds1374_driver);
248 }
249
250 static void __exit ds1374_exit(void)
251 {
252         i2c_del_driver(&ds1374_driver);
253 }
254
255 module_init(ds1374_init);
256 module_exit(ds1374_exit);
257
258 MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
259 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
260 MODULE_LICENSE("GPL");