1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  drivers/rtc/rtc-pcf8583.c
4 *
5 *  Copyright (C) 2000 Russell King
6 *  Copyright (C) 2008 Wolfram Sang & Juergen Beisert, Pengutronix
7 *
8 *  Driver for PCF8583 RTC & RAM chip
9 *
10 *  Converted to the generic RTC susbsystem by G. Liakhovetski (2006)
11 */
12#include <linux/module.h>
13#include <linux/i2c.h>
14#include <linux/slab.h>
15#include <linux/rtc.h>
16#include <linux/init.h>
17#include <linux/err.h>
18#include <linux/errno.h>
19#include <linux/bcd.h>
20
21struct rtc_mem {
22	unsigned int	loc;
23	unsigned int	nr;
24	unsigned char	*data;
25};
26
27struct pcf8583 {
28	struct rtc_device *rtc;
29	unsigned char ctrl;
30};
31
32#define CTRL_STOP	0x80
33#define CTRL_HOLD	0x40
34#define CTRL_32KHZ	0x00
35#define CTRL_MASK	0x08
36#define CTRL_ALARMEN	0x04
37#define CTRL_ALARM	0x02
38#define CTRL_TIMER	0x01
39
40
41static struct i2c_driver pcf8583_driver;
42
43#define get_ctrl(x)    ((struct pcf8583 *)i2c_get_clientdata(x))->ctrl
44#define set_ctrl(x, v) get_ctrl(x) = v
45
46#define CMOS_YEAR	(64 + 128)
47#define CMOS_CHECKSUM	(63)
48
49static int pcf8583_get_datetime(struct i2c_client *client, struct rtc_time *dt)
50{
51	unsigned char buf[8], addr[1] = { 1 };
52	struct i2c_msg msgs[2] = {
53		{
54			.addr = client->addr,
55			.flags = 0,
56			.len = 1,
57			.buf = addr,
58		}, {
59			.addr = client->addr,
60			.flags = I2C_M_RD,
61			.len = 6,
62			.buf = buf,
63		}
64	};
65	int ret;
66
67	memset(buf, 0, sizeof(buf));
68
69	ret = i2c_transfer(client->adapter, msgs, 2);
70	if (ret == 2) {
71		dt->tm_year = buf[4] >> 6;
72		dt->tm_wday = buf[5] >> 5;
73
74		buf[4] &= 0x3f;
75		buf[5] &= 0x1f;
76
77		dt->tm_sec = bcd2bin(buf[1]);
78		dt->tm_min = bcd2bin(buf[2]);
79		dt->tm_hour = bcd2bin(buf[3]);
80		dt->tm_mday = bcd2bin(buf[4]);
81		dt->tm_mon = bcd2bin(buf[5]) - 1;
82	}
83
84	return ret == 2 ? 0 : -EIO;
85}
86
87static int pcf8583_set_datetime(struct i2c_client *client, struct rtc_time *dt, int datetoo)
88{
89	unsigned char buf[8];
90	int ret, len = 6;
91
92	buf[0] = 0;
93	buf[1] = get_ctrl(client) | 0x80;
94	buf[2] = 0;
95	buf[3] = bin2bcd(dt->tm_sec);
96	buf[4] = bin2bcd(dt->tm_min);
97	buf[5] = bin2bcd(dt->tm_hour);
98
99	if (datetoo) {
100		len = 8;
101		buf[6] = bin2bcd(dt->tm_mday) | (dt->tm_year << 6);
102		buf[7] = bin2bcd(dt->tm_mon + 1)  | (dt->tm_wday << 5);
103	}
104
105	ret = i2c_master_send(client, (char *)buf, len);
106	if (ret != len)
107		return -EIO;
108
109	buf[1] = get_ctrl(client);
110	ret = i2c_master_send(client, (char *)buf, 2);
111
112	return ret == 2 ? 0 : -EIO;
113}
114
115static int pcf8583_get_ctrl(struct i2c_client *client, unsigned char *ctrl)
116{
117	*ctrl = get_ctrl(client);
118	return 0;
119}
120
121static int pcf8583_set_ctrl(struct i2c_client *client, unsigned char *ctrl)
122{
123	unsigned char buf[2];
124
125	buf[0] = 0;
126	buf[1] = *ctrl;
127	set_ctrl(client, *ctrl);
128
129	return i2c_master_send(client, (char *)buf, 2);
130}
131
132static int pcf8583_read_mem(struct i2c_client *client, struct rtc_mem *mem)
133{
134	unsigned char addr[1];
135	struct i2c_msg msgs[2] = {
136		{
137			.addr = client->addr,
138			.flags = 0,
139			.len = 1,
140			.buf = addr,
141		}, {
142			.addr = client->addr,
143			.flags = I2C_M_RD,
144			.len = mem->nr,
145			.buf = mem->data,
146		}
147	};
148
149	if (mem->loc < 8)
150		return -EINVAL;
151
152	addr[0] = mem->loc;
153
154	return i2c_transfer(client->adapter, msgs, 2) == 2 ? 0 : -EIO;
155}
156
157static int pcf8583_write_mem(struct i2c_client *client, struct rtc_mem *mem)
158{
159	unsigned char buf[9];
160	int ret;
161
162	if (mem->loc < 8 || mem->nr > 8)
163		return -EINVAL;
164
165	buf[0] = mem->loc;
166	memcpy(buf + 1, mem->data, mem->nr);
167
168	ret = i2c_master_send(client, buf, mem->nr + 1);
169	return ret == mem->nr + 1 ? 0 : -EIO;
170}
171
172static int pcf8583_rtc_read_time(struct device *dev, struct rtc_time *tm)
173{
174	struct i2c_client *client = to_i2c_client(dev);
175	unsigned char ctrl, year[2];
176	struct rtc_mem mem = {
177		.loc = CMOS_YEAR,
178		.nr = sizeof(year),
179		.data = year
180	};
181	int real_year, year_offset, err;
182
183	/*
184	 * Ensure that the RTC is running.
185	 */
186	pcf8583_get_ctrl(client, &ctrl);
187	if (ctrl & (CTRL_STOP | CTRL_HOLD)) {
188		unsigned char new_ctrl = ctrl & ~(CTRL_STOP | CTRL_HOLD);
189
190		dev_warn(dev, "resetting control %02x -> %02x\n",
191			ctrl, new_ctrl);
192
193		err = pcf8583_set_ctrl(client, &new_ctrl);
194		if (err < 0)
195			return err;
196	}
197
198	if (pcf8583_get_datetime(client, tm) ||
199	    pcf8583_read_mem(client, &mem))
200		return -EIO;
201
202	real_year = year[0];
203
204	/*
205	 * The RTC year holds the LSB two bits of the current
206	 * year, which should reflect the LSB two bits of the
207	 * CMOS copy of the year.  Any difference indicates
208	 * that we have to correct the CMOS version.
209	 */
210	year_offset = tm->tm_year - (real_year & 3);
211	if (year_offset < 0)
212		/*
213		 * RTC year wrapped.  Adjust it appropriately.
214		 */
215		year_offset += 4;
216
217	tm->tm_year = (real_year + year_offset + year[1] * 100) - 1900;
218
219	return 0;
220}
221
222static int pcf8583_rtc_set_time(struct device *dev, struct rtc_time *tm)
223{
224	struct i2c_client *client = to_i2c_client(dev);
225	unsigned char year[2], chk;
226	struct rtc_mem cmos_year  = {
227		.loc = CMOS_YEAR,
228		.nr = sizeof(year),
229		.data = year
230	};
231	struct rtc_mem cmos_check = {
232		.loc = CMOS_CHECKSUM,
233		.nr = 1,
234		.data = &chk
235	};
236	unsigned int proper_year = tm->tm_year + 1900;
237	int ret;
238
239	/*
240	 * The RTC's own 2-bit year must reflect the least
241	 * significant two bits of the CMOS year.
242	 */
243
244	ret = pcf8583_set_datetime(client, tm, 1);
245	if (ret)
246		return ret;
247
248	ret = pcf8583_read_mem(client, &cmos_check);
249	if (ret)
250		return ret;
251
252	ret = pcf8583_read_mem(client, &cmos_year);
253	if (ret)
254		return ret;
255
256	chk -= year[1] + year[0];
257
258	year[1] = proper_year / 100;
259	year[0] = proper_year % 100;
260
261	chk += year[1] + year[0];
262
263	ret = pcf8583_write_mem(client, &cmos_year);
264
265	if (ret)
266		return ret;
267
268	ret = pcf8583_write_mem(client, &cmos_check);
269
270	return ret;
271}
272
273static const struct rtc_class_ops pcf8583_rtc_ops = {
274	.read_time	= pcf8583_rtc_read_time,
275	.set_time	= pcf8583_rtc_set_time,
276};
277
278static int pcf8583_probe(struct i2c_client *client)
279{
280	struct pcf8583 *pcf8583;
281
282	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
283		return -ENODEV;
284
285	pcf8583 = devm_kzalloc(&client->dev, sizeof(struct pcf8583),
286				GFP_KERNEL);
287	if (!pcf8583)
288		return -ENOMEM;
289
290	i2c_set_clientdata(client, pcf8583);
291
292	pcf8583->rtc = devm_rtc_device_register(&client->dev,
293				pcf8583_driver.driver.name,
294				&pcf8583_rtc_ops, THIS_MODULE);
295
296	return PTR_ERR_OR_ZERO(pcf8583->rtc);
297}
298
299static const struct i2c_device_id pcf8583_id[] = {
300	{ "pcf8583", 0 },
301	{ }
302};
303MODULE_DEVICE_TABLE(i2c, pcf8583_id);
304
305static struct i2c_driver pcf8583_driver = {
306	.driver = {
307		.name	= "pcf8583",
308	},
309	.probe		= pcf8583_probe,
310	.id_table	= pcf8583_id,
311};
312
313module_i2c_driver(pcf8583_driver);
314
315MODULE_AUTHOR("Russell King");
316MODULE_DESCRIPTION("PCF8583 I2C RTC driver");
317MODULE_LICENSE("GPL");
318