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 void ds1374_set_work(void *arg)
144 {
145 ulong t1, t2;
146 int limit = 10; /* arbitrary retry limit */
147
148 t1 = *(ulong *) arg;
149
150 mutex_lock(&ds1374_mutex);
151
152 /*
153 * Since the writes are being performed one byte at a time using
154 * the SMBus vs a 4-byte i2c transfer, there is a chance that a
155 * carry will occur during the write. To detect this, the write
156 * value is read back and compared.
157 */
158 do {
159 ds1374_write_rtc(t1);
160 t2 = ds1374_read_rtc();
161 } while (t1 != t2 && limit--);
162
163 mutex_unlock(&ds1374_mutex);
164
165 if (t1 != t2)
166 dev_warn(&save_client->dev,
167 "can't confirm time set from rtc chip\n");
168 }
169
170 static ulong new_time;
171
172 static struct workqueue_struct *ds1374_workqueue;
173
174 static DECLARE_WORK(ds1374_work, ds1374_set_work, &new_time);
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(&new_time);
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");
264
This page was automatically generated by the
LXR engine.
Visit the LXR main site for more
information.