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
46static DEFINE_MUTEX(ds1374_mutex);
47
48static struct i2c_driver ds1374_driver;
49static struct i2c_client *save_client;
50
51static unsigned short ignore[] = { I2C_CLIENT_END };
52static unsigned short normal_addr[] = { 0x68, I2C_CLIENT_END };
53
54static struct i2c_client_address_data addr_data = {
55	.normal_i2c = normal_addr,
56	.probe = ignore,
57	.ignore = ignore,
58};
59
60static 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
77static 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
92static 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
114ulong 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
143static ulong new_time;
144
145static 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
172static struct workqueue_struct *ds1374_workqueue;
173
174static DECLARE_WORK(ds1374_work, ds1374_set_work);
175
176int 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 */
195static 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	if (!ds1374_workqueue) {
211		kfree(client);
212		return -ENOMEM;	/* most expected reason */
213	}
214
215	if ((rc = i2c_attach_client(client)) != 0) {
216		kfree(client);
217		return rc;
218	}
219
220	save_client = client;
221
222	ds1374_check_rtc_status();
223
224	return 0;
225}
226
227static int ds1374_attach(struct i2c_adapter *adap)
228{
229	return i2c_probe(adap, &addr_data, ds1374_probe);
230}
231
232static int ds1374_detach(struct i2c_client *client)
233{
234	int rc;
235
236	if ((rc = i2c_detach_client(client)) == 0) {
237		kfree(i2c_get_clientdata(client));
238		destroy_workqueue(ds1374_workqueue);
239	}
240	return rc;
241}
242
243static struct i2c_driver ds1374_driver = {
244	.driver = {
245		.name	= DS1374_DRV_NAME,
246	},
247	.id = I2C_DRIVERID_DS1374,
248	.attach_adapter = ds1374_attach,
249	.detach_client = ds1374_detach,
250};
251
252static int __init ds1374_init(void)
253{
254	return i2c_add_driver(&ds1374_driver);
255}
256
257static void __exit ds1374_exit(void)
258{
259	i2c_del_driver(&ds1374_driver);
260}
261
262module_init(ds1374_init);
263module_exit(ds1374_exit);
264
265MODULE_AUTHOR("Randy Vinson <rvinson@mvista.com>");
266MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC I2C Client Driver");
267MODULE_LICENSE("GPL");
268