xref: /openbmc/linux/drivers/rtc/rtc-max6900.c (revision 4800cd83)
1 /*
2  * rtc class driver for the Maxim MAX6900 chip
3  *
4  * Author: Dale Farnsworth <dale@farnsworth.org>
5  *
6  * based on previously existing rtc class drivers
7  *
8  * 2007 (c) MontaVista, Software, Inc.  This file is licensed under
9  * the terms of the GNU General Public License version 2.  This program
10  * is licensed "as is" without any warranty of any kind, whether express
11  * or implied.
12  */
13 
14 #include <linux/module.h>
15 #include <linux/i2c.h>
16 #include <linux/bcd.h>
17 #include <linux/rtc.h>
18 #include <linux/delay.h>
19 
20 #define DRV_VERSION "0.2"
21 
22 /*
23  * register indices
24  */
25 #define MAX6900_REG_SC			0	/* seconds      00-59 */
26 #define MAX6900_REG_MN			1	/* minutes      00-59 */
27 #define MAX6900_REG_HR			2	/* hours        00-23 */
28 #define MAX6900_REG_DT			3	/* day of month 00-31 */
29 #define MAX6900_REG_MO			4	/* month        01-12 */
30 #define MAX6900_REG_DW			5	/* day of week   1-7  */
31 #define MAX6900_REG_YR			6	/* year         00-99 */
32 #define MAX6900_REG_CT			7	/* control */
33 						/* register 8 is undocumented */
34 #define MAX6900_REG_CENTURY		9	/* century */
35 #define MAX6900_REG_LEN			10
36 
37 #define MAX6900_BURST_LEN		8	/* can burst r/w first 8 regs */
38 
39 #define MAX6900_REG_CT_WP		(1 << 7)	/* Write Protect */
40 
41 /*
42  * register read/write commands
43  */
44 #define MAX6900_REG_CONTROL_WRITE	0x8e
45 #define MAX6900_REG_CENTURY_WRITE	0x92
46 #define MAX6900_REG_CENTURY_READ	0x93
47 #define MAX6900_REG_RESERVED_READ	0x96
48 #define MAX6900_REG_BURST_WRITE		0xbe
49 #define MAX6900_REG_BURST_READ		0xbf
50 
51 #define MAX6900_IDLE_TIME_AFTER_WRITE	3	/* specification says 2.5 mS */
52 
53 static struct i2c_driver max6900_driver;
54 
55 static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
56 {
57 	u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
58 	u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
59 	struct i2c_msg msgs[4] = {
60 		{
61 		 .addr = client->addr,
62 		 .flags = 0,	/* write */
63 		 .len = sizeof(reg_burst_read),
64 		 .buf = reg_burst_read}
65 		,
66 		{
67 		 .addr = client->addr,
68 		 .flags = I2C_M_RD,
69 		 .len = MAX6900_BURST_LEN,
70 		 .buf = buf}
71 		,
72 		{
73 		 .addr = client->addr,
74 		 .flags = 0,	/* write */
75 		 .len = sizeof(reg_century_read),
76 		 .buf = reg_century_read}
77 		,
78 		{
79 		 .addr = client->addr,
80 		 .flags = I2C_M_RD,
81 		 .len = sizeof(buf[MAX6900_REG_CENTURY]),
82 		 .buf = &buf[MAX6900_REG_CENTURY]
83 		 }
84 	};
85 	int rc;
86 
87 	rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
88 	if (rc != ARRAY_SIZE(msgs)) {
89 		dev_err(&client->dev, "%s: register read failed\n", __func__);
90 		return -EIO;
91 	}
92 	return 0;
93 }
94 
95 static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
96 {
97 	u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
98 	struct i2c_msg century_msgs[1] = {
99 		{
100 		 .addr = client->addr,
101 		 .flags = 0,	/* write */
102 		 .len = sizeof(i2c_century_buf),
103 		 .buf = i2c_century_buf}
104 	};
105 	u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
106 	struct i2c_msg burst_msgs[1] = {
107 		{
108 		 .addr = client->addr,
109 		 .flags = 0,	/* write */
110 		 .len = sizeof(i2c_burst_buf),
111 		 .buf = i2c_burst_buf}
112 	};
113 	int rc;
114 
115 	/*
116 	 * We have to make separate calls to i2c_transfer because of
117 	 * the need to delay after each write to the chip.  Also,
118 	 * we write the century byte first, since we set the write-protect
119 	 * bit as part of the burst write.
120 	 */
121 	i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
122 
123 	rc = i2c_transfer(client->adapter, century_msgs,
124 			  ARRAY_SIZE(century_msgs));
125 	if (rc != ARRAY_SIZE(century_msgs))
126 		goto write_failed;
127 
128 	msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
129 
130 	memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
131 
132 	rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
133 	if (rc != ARRAY_SIZE(burst_msgs))
134 		goto write_failed;
135 	msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
136 
137 	return 0;
138 
139  write_failed:
140 	dev_err(&client->dev, "%s: register write failed\n", __func__);
141 	return -EIO;
142 }
143 
144 static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
145 {
146 	int rc;
147 	u8 regs[MAX6900_REG_LEN];
148 
149 	rc = max6900_i2c_read_regs(client, regs);
150 	if (rc < 0)
151 		return rc;
152 
153 	tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
154 	tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
155 	tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
156 	tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
157 	tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
158 	tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
159 		      bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
160 	tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
161 
162 	return rtc_valid_tm(tm);
163 }
164 
165 static int max6900_i2c_clear_write_protect(struct i2c_client *client)
166 {
167 	int rc;
168 	rc = i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
169 	if (rc < 0) {
170 		dev_err(&client->dev, "%s: control register write failed\n",
171 			__func__);
172 		return -EIO;
173 	}
174 	return 0;
175 }
176 
177 static int
178 max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
179 {
180 	u8 regs[MAX6900_REG_LEN];
181 	int rc;
182 
183 	rc = max6900_i2c_clear_write_protect(client);
184 	if (rc < 0)
185 		return rc;
186 
187 	regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
188 	regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
189 	regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
190 	regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
191 	regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
192 	regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
193 	regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
194 	regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
195 	/* set write protect */
196 	regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
197 
198 	rc = max6900_i2c_write_regs(client, regs);
199 	if (rc < 0)
200 		return rc;
201 
202 	return 0;
203 }
204 
205 static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
206 {
207 	return max6900_i2c_read_time(to_i2c_client(dev), tm);
208 }
209 
210 static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
211 {
212 	return max6900_i2c_set_time(to_i2c_client(dev), tm);
213 }
214 
215 static int max6900_remove(struct i2c_client *client)
216 {
217 	struct rtc_device *rtc = i2c_get_clientdata(client);
218 
219 	if (rtc)
220 		rtc_device_unregister(rtc);
221 
222 	return 0;
223 }
224 
225 static const struct rtc_class_ops max6900_rtc_ops = {
226 	.read_time = max6900_rtc_read_time,
227 	.set_time = max6900_rtc_set_time,
228 };
229 
230 static int
231 max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
232 {
233 	struct rtc_device *rtc;
234 
235 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
236 		return -ENODEV;
237 
238 	dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
239 
240 	rtc = rtc_device_register(max6900_driver.driver.name,
241 				  &client->dev, &max6900_rtc_ops, THIS_MODULE);
242 	if (IS_ERR(rtc))
243 		return PTR_ERR(rtc);
244 
245 	i2c_set_clientdata(client, rtc);
246 
247 	return 0;
248 }
249 
250 static struct i2c_device_id max6900_id[] = {
251 	{ "max6900", 0 },
252 	{ }
253 };
254 
255 static struct i2c_driver max6900_driver = {
256 	.driver = {
257 		   .name = "rtc-max6900",
258 		   },
259 	.probe = max6900_probe,
260 	.remove = max6900_remove,
261 	.id_table = max6900_id,
262 };
263 
264 static int __init max6900_init(void)
265 {
266 	return i2c_add_driver(&max6900_driver);
267 }
268 
269 static void __exit max6900_exit(void)
270 {
271 	i2c_del_driver(&max6900_driver);
272 }
273 
274 MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
275 MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
276 MODULE_LICENSE("GPL");
277 MODULE_VERSION(DRV_VERSION);
278 
279 module_init(max6900_init);
280 module_exit(max6900_exit);
281