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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 { .name = "pcf8583" },
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");