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
24struct rtc_mem {
25	unsigned int	loc;
26	unsigned int	nr;
27	unsigned char	*data;
28};
29
30struct 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
44static 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
52static 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
90static 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
118static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
119{
120	*ctrl = get_ctrl(client);
121	return 0;
122}
123
124static 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
135static 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
160static 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
175static 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
225static 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
276static const struct rtc_class_ops pcf8583_rtc_ops = {
277	.read_time	= pcf8583_rtc_read_time,
278	.set_time	= pcf8583_rtc_set_time,
279};
280
281static 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
303static const struct i2c_device_id pcf8583_id[] = {
304	{ "pcf8583", 0 },
305	{ }
306};
307MODULE_DEVICE_TABLE(i2c, pcf8583_id);
308
309static struct i2c_driver pcf8583_driver = {
310	.driver = {
311		.name	= "pcf8583",
312		.owner	= THIS_MODULE,
313	},
314	.probe		= pcf8583_probe,
315	.id_table	= pcf8583_id,
316};
317
318module_i2c_driver(pcf8583_driver);
319
320MODULE_AUTHOR("Russell King");
321MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
322MODULE_LICENSE("GPL");
323