1 /*
2  *  drivers/rtc/rtc-pcf8583.c
3  *
4  *  Copyright (C) 2000 Russell King
5  *  Copyright (C) 2008 Wolfram Sang & Juergen Beisert, Pengutronix
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  *  Driver for PCF8583 RTC & RAM chip
12  *
13  *  Converted to the generic RTC susbsystem by G. Liakhovetski (2006)
14  */
15 #include <linux/module.h>
16 #include <linux/i2c.h>
17 #include <linux/slab.h>
18 #include <linux/rtc.h>
19 #include <linux/init.h>
20 #include <linux/err.h>
21 #include <linux/errno.h>
22 #include <linux/bcd.h>
23 
24 struct rtc_mem {
25 	unsigned int	loc;
26 	unsigned int	nr;
27 	unsigned char	*data;
28 };
29 
30 struct pcf8583 {
31 	struct rtc_device *rtc;
32 	unsigned char ctrl;
33 };
34 
35 #define CTRL_STOP	0x80
36 #define CTRL_HOLD	0x40
37 #define CTRL_32KHZ	0x00
38 #define CTRL_MASK	0x08
39 #define CTRL_ALARMEN	0x04
40 #define CTRL_ALARM	0x02
41 #define CTRL_TIMER	0x01
42 
43 
44 static struct i2c_driver pcf8583_driver;
45 
46 #define get_ctrl(x)    ((struct pcf8583 *)i2c_get_clientdata(x))->ctrl
47 #define set_ctrl(x, v) get_ctrl(x) = v
48 
49 #define CMOS_YEAR	(64 + 128)
50 #define CMOS_CHECKSUM	(63)
51 
pcf8583_get_datetime(struct i2c_client * client,struct rtc_time * dt)52 static int pcf8583_get_datetime(struct i2c_client *client, struct rtc_time *dt)
53 {
54 	unsigned char buf[8], addr[1] = { 1 };
55 	struct i2c_msg msgs[2] = {
56 		{
57 			.addr = client->addr,
58 			.flags = 0,
59 			.len = 1,
60 			.buf = addr,
61 		}, {
62 			.addr = client->addr,
63 			.flags = I2C_M_RD,
64 			.len = 6,
65 			.buf = buf,
66 		}
67 	};
68 	int ret;
69 
70 	memset(buf, 0, sizeof(buf));
71 
72 	ret = i2c_transfer(client->adapter, msgs, 2);
73 	if (ret == 2) {
74 		dt->tm_year = buf[4] >> 6;
75 		dt->tm_wday = buf[5] >> 5;
76 
77 		buf[4] &= 0x3f;
78 		buf[5] &= 0x1f;
79 
80 		dt->tm_sec = bcd2bin(buf[1]);
81 		dt->tm_min = bcd2bin(buf[2]);
82 		dt->tm_hour = bcd2bin(buf[3]);
83 		dt->tm_mday = bcd2bin(buf[4]);
84 		dt->tm_mon = bcd2bin(buf[5]) - 1;
85 	}
86 
87 	return ret == 2 ? 0 : -EIO;
88 }
89 
pcf8583_set_datetime(struct i2c_client * client,struct rtc_time * dt,int datetoo)90 static int pcf8583_set_datetime(struct i2c_client *client, struct rtc_time *dt, int datetoo)
91 {
92 	unsigned char buf[8];
93 	int ret, len = 6;
94 
95 	buf[0] = 0;
96 	buf[1] = get_ctrl(client) | 0x80;
97 	buf[2] = 0;
98 	buf[3] = bin2bcd(dt->tm_sec);
99 	buf[4] = bin2bcd(dt->tm_min);
100 	buf[5] = bin2bcd(dt->tm_hour);
101 
102 	if (datetoo) {
103 		len = 8;
104 		buf[6] = bin2bcd(dt->tm_mday) | (dt->tm_year << 6);
105 		buf[7] = bin2bcd(dt->tm_mon + 1)  | (dt->tm_wday << 5);
106 	}
107 
108 	ret = i2c_master_send(client, (char *)buf, len);
109 	if (ret != len)
110 		return -EIO;
111 
112 	buf[1] = get_ctrl(client);
113 	ret = i2c_master_send(client, (char *)buf, 2);
114 
115 	return ret == 2 ? 0 : -EIO;
116 }
117 
pcf8583_get_ctrl(struct i2c_client * client,unsigned char * ctrl)118 static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
119 {
120 	*ctrl = get_ctrl(client);
121 	return 0;
122 }
123 
pcf8583_set_ctrl(struct i2c_client * client,unsigned char * ctrl)124 static int pcf8583_set_ctrl(struct i2c_client *client, unsigned char *ctrl)
125 {
126 	unsigned char buf[2];
127 
128 	buf[0] = 0;
129 	buf[1] = *ctrl;
130 	set_ctrl(client, *ctrl);
131 
132 	return i2c_master_send(client, (char *)buf, 2);
133 }
134 
pcf8583_read_mem(struct i2c_client * client,struct rtc_mem * mem)135 static int pcf8583_read_mem(struct i2c_client *client, struct rtc_mem *mem)
136 {
137 	unsigned char addr[1];
138 	struct i2c_msg msgs[2] = {
139 		{
140 			.addr = client->addr,
141 			.flags = 0,
142 			.len = 1,
143 			.buf = addr,
144 		}, {
145 			.addr = client->addr,
146 			.flags = I2C_M_RD,
147 			.len = mem->nr,
148 			.buf = mem->data,
149 		}
150 	};
151 
152 	if (mem->loc < 8)
153 		return -EINVAL;
154 
155 	addr[0] = mem->loc;
156 
157 	return i2c_transfer(client->adapter, msgs, 2) == 2 ? 0 : -EIO;
158 }
159 
pcf8583_write_mem(struct i2c_client * client,struct rtc_mem * mem)160 static int pcf8583_write_mem(struct i2c_client *client, struct rtc_mem *mem)
161 {
162 	unsigned char buf[9];
163 	int ret;
164 
165 	if (mem->loc < 8 || mem->nr > 8)
166 		return -EINVAL;
167 
168 	buf[0] = mem->loc;
169 	memcpy(buf + 1, mem->data, mem->nr);
170 
171 	ret = i2c_master_send(client, buf, mem->nr + 1);
172 	return ret == mem->nr + 1 ? 0 : -EIO;
173 }
174 
pcf8583_rtc_read_time(struct device * dev,struct rtc_time * tm)175 static int pcf8583_rtc_read_time(struct device *dev, struct rtc_time *tm)
176 {
177 	struct i2c_client *client = to_i2c_client(dev);
178 	unsigned char ctrl, year[2];
179 	struct rtc_mem mem = {
180 		.loc = CMOS_YEAR,
181 		.nr = sizeof(year),
182 		.data = year
183 	};
184 	int real_year, year_offset, err;
185 
186 	/*
187 	 * Ensure that the RTC is running.
188 	 */
189 	pcf8583_get_ctrl(client, &ctrl);
190 	if (ctrl & (CTRL_STOP | CTRL_HOLD)) {
191 		unsigned char new_ctrl = ctrl & ~(CTRL_STOP | CTRL_HOLD);
192 
193 		dev_warn(dev, "resetting control %02x -> %02x\n",
194 			ctrl, new_ctrl);
195 
196 		err = pcf8583_set_ctrl(client, &new_ctrl);
197 		if (err < 0)
198 			return err;
199 	}
200 
201 	if (pcf8583_get_datetime(client, tm) ||
202 	    pcf8583_read_mem(client, &mem))
203 		return -EIO;
204 
205 	real_year = year[0];
206 
207 	/*
208 	 * The RTC year holds the LSB two bits of the current
209 	 * year, which should reflect the LSB two bits of the
210 	 * CMOS copy of the year.  Any difference indicates
211 	 * that we have to correct the CMOS version.
212 	 */
213 	year_offset = tm->tm_year - (real_year & 3);
214 	if (year_offset < 0)
215 		/*
216 		 * RTC year wrapped.  Adjust it appropriately.
217 		 */
218 		year_offset += 4;
219 
220 	tm->tm_year = (real_year + year_offset + year[1] * 100) - 1900;
221 
222 	return 0;
223 }
224 
pcf8583_rtc_set_time(struct device * dev,struct rtc_time * tm)225 static int pcf8583_rtc_set_time(struct device *dev, struct rtc_time *tm)
226 {
227 	struct i2c_client *client = to_i2c_client(dev);
228 	unsigned char year[2], chk;
229 	struct rtc_mem cmos_year  = {
230 		.loc = CMOS_YEAR,
231 		.nr = sizeof(year),
232 		.data = year
233 	};
234 	struct rtc_mem cmos_check = {
235 		.loc = CMOS_CHECKSUM,
236 		.nr = 1,
237 		.data = &chk
238 	};
239 	unsigned int proper_year = tm->tm_year + 1900;
240 	int ret;
241 
242 	/*
243 	 * The RTC's own 2-bit year must reflect the least
244 	 * significant two bits of the CMOS year.
245 	 */
246 
247 	ret = pcf8583_set_datetime(client, tm, 1);
248 	if (ret)
249 		return ret;
250 
251 	ret = pcf8583_read_mem(client, &cmos_check);
252 	if (ret)
253 		return ret;
254 
255 	ret = pcf8583_read_mem(client, &cmos_year);
256 	if (ret)
257 		return ret;
258 
259 	chk -= year[1] + year[0];
260 
261 	year[1] = proper_year / 100;
262 	year[0] = proper_year % 100;
263 
264 	chk += year[1] + year[0];
265 
266 	ret = pcf8583_write_mem(client, &cmos_year);
267 
268 	if (ret)
269 		return ret;
270 
271 	ret = pcf8583_write_mem(client, &cmos_check);
272 
273 	return ret;
274 }
275 
276 static const struct rtc_class_ops pcf8583_rtc_ops = {
277 	.read_time	= pcf8583_rtc_read_time,
278 	.set_time	= pcf8583_rtc_set_time,
279 };
280 
pcf8583_probe(struct i2c_client * client,const struct i2c_device_id * id)281 static int pcf8583_probe(struct i2c_client *client,
282 				const struct i2c_device_id *id)
283 {
284 	struct pcf8583 *pcf8583;
285 
286 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
287 		return -ENODEV;
288 
289 	pcf8583 = devm_kzalloc(&client->dev, sizeof(struct pcf8583),
290 				GFP_KERNEL);
291 	if (!pcf8583)
292 		return -ENOMEM;
293 
294 	i2c_set_clientdata(client, pcf8583);
295 
296 	pcf8583->rtc = devm_rtc_device_register(&client->dev,
297 				pcf8583_driver.driver.name,
298 				&pcf8583_rtc_ops, THIS_MODULE);
299 
300 	return PTR_ERR_OR_ZERO(pcf8583->rtc);
301 }
302 
303 static const struct i2c_device_id pcf8583_id[] = {
304 	{ "pcf8583", 0 },
305 	{ }
306 };
307 MODULE_DEVICE_TABLE(i2c, pcf8583_id);
308 
309 static struct i2c_driver pcf8583_driver = {
310 	.driver = {
311 		.name	= "pcf8583",
312 	},
313 	.probe		= pcf8583_probe,
314 	.id_table	= pcf8583_id,
315 };
316 
317 module_i2c_driver(pcf8583_driver);
318 
319 MODULE_AUTHOR("Russell King");
320 MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
321 MODULE_LICENSE("GPL");
322