Loading...
1/*
2 * SPI Driver for Microchip MCP795 RTC
3 *
4 * Copyright (C) Josef Gajdusek <atx@atx.name>
5 *
6 * based on other Linux RTC drivers
7 *
8 * Device datasheet:
9 * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
14 *
15 * */
16
17#include <linux/module.h>
18#include <linux/kernel.h>
19#include <linux/device.h>
20#include <linux/printk.h>
21#include <linux/spi/spi.h>
22#include <linux/rtc.h>
23#include <linux/of.h>
24
25/* MCP795 Instructions, see datasheet table 3-1 */
26#define MCP795_EEREAD 0x03
27#define MCP795_EEWRITE 0x02
28#define MCP795_EEWRDI 0x04
29#define MCP795_EEWREN 0x06
30#define MCP795_SRREAD 0x05
31#define MCP795_SRWRITE 0x01
32#define MCP795_READ 0x13
33#define MCP795_WRITE 0x12
34#define MCP795_UNLOCK 0x14
35#define MCP795_IDWRITE 0x32
36#define MCP795_IDREAD 0x33
37#define MCP795_CLRWDT 0x44
38#define MCP795_CLRRAM 0x54
39
40#define MCP795_ST_BIT 0x80
41#define MCP795_24_BIT 0x40
42
43static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
44{
45 struct spi_device *spi = to_spi_device(dev);
46 int ret;
47 u8 tx[2];
48
49 tx[0] = MCP795_READ;
50 tx[1] = addr;
51 ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
52
53 if (ret)
54 dev_err(dev, "Failed reading %d bytes from address %x.\n",
55 count, addr);
56
57 return ret;
58}
59
60static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
61{
62 struct spi_device *spi = to_spi_device(dev);
63 int ret;
64 u8 tx[2 + count];
65
66 tx[0] = MCP795_WRITE;
67 tx[1] = addr;
68 memcpy(&tx[2], data, count);
69
70 ret = spi_write(spi, tx, 2 + count);
71
72 if (ret)
73 dev_err(dev, "Failed to write %d bytes to address %x.\n",
74 count, addr);
75
76 return ret;
77}
78
79static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
80{
81 int ret;
82 u8 tmp;
83
84 ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
85 if (ret)
86 return ret;
87
88 if ((tmp & mask) != state) {
89 tmp = (tmp & ~mask) | state;
90 ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
91 }
92
93 return ret;
94}
95
96static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
97{
98 int ret;
99 u8 data[7];
100
101 /* Read first, so we can leave config bits untouched */
102 ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
103
104 if (ret)
105 return ret;
106
107 data[0] = (data[0] & 0x80) | ((tim->tm_sec / 10) << 4) | (tim->tm_sec % 10);
108 data[1] = (data[1] & 0x80) | ((tim->tm_min / 10) << 4) | (tim->tm_min % 10);
109 data[2] = ((tim->tm_hour / 10) << 4) | (tim->tm_hour % 10);
110 data[4] = ((tim->tm_mday / 10) << 4) | ((tim->tm_mday) % 10);
111 data[5] = (data[5] & 0x10) | (tim->tm_mon / 10) | (tim->tm_mon % 10);
112
113 if (tim->tm_year > 100)
114 tim->tm_year -= 100;
115
116 data[6] = ((tim->tm_year / 10) << 4) | (tim->tm_year % 10);
117
118 ret = mcp795_rtcc_write(dev, 0x01, data, sizeof(data));
119
120 if (ret)
121 return ret;
122
123 dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
124 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
125 tim->tm_hour, tim->tm_min, tim->tm_sec);
126
127 return 0;
128}
129
130static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
131{
132 int ret;
133 u8 data[7];
134
135 ret = mcp795_rtcc_read(dev, 0x01, data, sizeof(data));
136
137 if (ret)
138 return ret;
139
140 tim->tm_sec = ((data[0] & 0x70) >> 4) * 10 + (data[0] & 0x0f);
141 tim->tm_min = ((data[1] & 0x70) >> 4) * 10 + (data[1] & 0x0f);
142 tim->tm_hour = ((data[2] & 0x30) >> 4) * 10 + (data[2] & 0x0f);
143 tim->tm_mday = ((data[4] & 0x30) >> 4) * 10 + (data[4] & 0x0f);
144 tim->tm_mon = ((data[5] & 0x10) >> 4) * 10 + (data[5] & 0x0f);
145 tim->tm_year = ((data[6] & 0xf0) >> 4) * 10 + (data[6] & 0x0f) + 100; /* Assume we are in 20xx */
146
147 dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
148 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
149 tim->tm_hour, tim->tm_min, tim->tm_sec);
150
151 return rtc_valid_tm(tim);
152}
153
154static struct rtc_class_ops mcp795_rtc_ops = {
155 .read_time = mcp795_read_time,
156 .set_time = mcp795_set_time
157};
158
159static int mcp795_probe(struct spi_device *spi)
160{
161 struct rtc_device *rtc;
162 int ret;
163
164 spi->mode = SPI_MODE_0;
165 spi->bits_per_word = 8;
166 ret = spi_setup(spi);
167 if (ret) {
168 dev_err(&spi->dev, "Unable to setup SPI\n");
169 return ret;
170 }
171
172 /* Start the oscillator */
173 mcp795_rtcc_set_bits(&spi->dev, 0x01, MCP795_ST_BIT, MCP795_ST_BIT);
174 /* Clear the 12 hour mode flag*/
175 mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
176
177 rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
178 &mcp795_rtc_ops, THIS_MODULE);
179 if (IS_ERR(rtc))
180 return PTR_ERR(rtc);
181
182 spi_set_drvdata(spi, rtc);
183
184 return 0;
185}
186
187#ifdef CONFIG_OF
188static const struct of_device_id mcp795_of_match[] = {
189 { .compatible = "maxim,mcp795" },
190 { }
191};
192MODULE_DEVICE_TABLE(of, mcp795_of_match);
193#endif
194
195static struct spi_driver mcp795_driver = {
196 .driver = {
197 .name = "rtc-mcp795",
198 .of_match_table = of_match_ptr(mcp795_of_match),
199 },
200 .probe = mcp795_probe,
201};
202
203module_spi_driver(mcp795_driver);
204
205MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
206MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>");
207MODULE_LICENSE("GPL");
208MODULE_ALIAS("spi:mcp795");
1/*
2 * SPI Driver for Microchip MCP795 RTC
3 *
4 * Copyright (C) Josef Gajdusek <atx@atx.name>
5 *
6 * based on other Linux RTC drivers
7 *
8 * Device datasheet:
9 * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
14 *
15 */
16
17#include <linux/module.h>
18#include <linux/kernel.h>
19#include <linux/device.h>
20#include <linux/printk.h>
21#include <linux/spi/spi.h>
22#include <linux/rtc.h>
23#include <linux/of.h>
24#include <linux/bcd.h>
25#include <linux/delay.h>
26
27/* MCP795 Instructions, see datasheet table 3-1 */
28#define MCP795_EEREAD 0x03
29#define MCP795_EEWRITE 0x02
30#define MCP795_EEWRDI 0x04
31#define MCP795_EEWREN 0x06
32#define MCP795_SRREAD 0x05
33#define MCP795_SRWRITE 0x01
34#define MCP795_READ 0x13
35#define MCP795_WRITE 0x12
36#define MCP795_UNLOCK 0x14
37#define MCP795_IDWRITE 0x32
38#define MCP795_IDREAD 0x33
39#define MCP795_CLRWDT 0x44
40#define MCP795_CLRRAM 0x54
41
42/* MCP795 RTCC registers, see datasheet table 4-1 */
43#define MCP795_REG_SECONDS 0x01
44#define MCP795_REG_DAY 0x04
45#define MCP795_REG_MONTH 0x06
46#define MCP795_REG_CONTROL 0x08
47
48#define MCP795_ST_BIT BIT(7)
49#define MCP795_24_BIT BIT(6)
50#define MCP795_LP_BIT BIT(5)
51#define MCP795_EXTOSC_BIT BIT(3)
52#define MCP795_OSCON_BIT BIT(5)
53
54static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)
55{
56 struct spi_device *spi = to_spi_device(dev);
57 int ret;
58 u8 tx[2];
59
60 tx[0] = MCP795_READ;
61 tx[1] = addr;
62 ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);
63
64 if (ret)
65 dev_err(dev, "Failed reading %d bytes from address %x.\n",
66 count, addr);
67
68 return ret;
69}
70
71static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)
72{
73 struct spi_device *spi = to_spi_device(dev);
74 int ret;
75 u8 tx[2 + count];
76
77 tx[0] = MCP795_WRITE;
78 tx[1] = addr;
79 memcpy(&tx[2], data, count);
80
81 ret = spi_write(spi, tx, 2 + count);
82
83 if (ret)
84 dev_err(dev, "Failed to write %d bytes to address %x.\n",
85 count, addr);
86
87 return ret;
88}
89
90static int mcp795_rtcc_set_bits(struct device *dev, u8 addr, u8 mask, u8 state)
91{
92 int ret;
93 u8 tmp;
94
95 ret = mcp795_rtcc_read(dev, addr, &tmp, 1);
96 if (ret)
97 return ret;
98
99 if ((tmp & mask) != state) {
100 tmp = (tmp & ~mask) | state;
101 ret = mcp795_rtcc_write(dev, addr, &tmp, 1);
102 }
103
104 return ret;
105}
106
107static int mcp795_stop_oscillator(struct device *dev, bool *extosc)
108{
109 int retries = 5;
110 int ret;
111 u8 data;
112
113 ret = mcp795_rtcc_set_bits(dev, MCP795_REG_SECONDS, MCP795_ST_BIT, 0);
114 if (ret)
115 return ret;
116 ret = mcp795_rtcc_read(dev, MCP795_REG_CONTROL, &data, 1);
117 if (ret)
118 return ret;
119 *extosc = !!(data & MCP795_EXTOSC_BIT);
120 ret = mcp795_rtcc_set_bits(
121 dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, 0);
122 if (ret)
123 return ret;
124 /* wait for the OSCON bit to clear */
125 do {
126 usleep_range(700, 800);
127 ret = mcp795_rtcc_read(dev, MCP795_REG_DAY, &data, 1);
128 if (ret)
129 break;
130 if (!(data & MCP795_OSCON_BIT))
131 break;
132
133 } while (--retries);
134
135 return !retries ? -EIO : ret;
136}
137
138static int mcp795_start_oscillator(struct device *dev, bool *extosc)
139{
140 if (extosc) {
141 u8 data = *extosc ? MCP795_EXTOSC_BIT : 0;
142 int ret;
143
144 ret = mcp795_rtcc_set_bits(
145 dev, MCP795_REG_CONTROL, MCP795_EXTOSC_BIT, data);
146 if (ret)
147 return ret;
148 }
149 return mcp795_rtcc_set_bits(
150 dev, MCP795_REG_SECONDS, MCP795_ST_BIT, MCP795_ST_BIT);
151}
152
153static int mcp795_set_time(struct device *dev, struct rtc_time *tim)
154{
155 int ret;
156 u8 data[7];
157 bool extosc;
158
159 /* Stop RTC and store current value of EXTOSC bit */
160 ret = mcp795_stop_oscillator(dev, &extosc);
161 if (ret)
162 return ret;
163
164 /* Read first, so we can leave config bits untouched */
165 ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
166
167 if (ret)
168 return ret;
169
170 data[0] = (data[0] & 0x80) | bin2bcd(tim->tm_sec);
171 data[1] = (data[1] & 0x80) | bin2bcd(tim->tm_min);
172 data[2] = bin2bcd(tim->tm_hour);
173 data[4] = bin2bcd(tim->tm_mday);
174 data[5] = (data[5] & MCP795_LP_BIT) | bin2bcd(tim->tm_mon + 1);
175
176 if (tim->tm_year > 100)
177 tim->tm_year -= 100;
178
179 data[6] = bin2bcd(tim->tm_year);
180
181 /* Always write the date and month using a separate Write command.
182 * This is a workaround for a know silicon issue that some combinations
183 * of date and month values may result in the date being reset to 1.
184 */
185 ret = mcp795_rtcc_write(dev, MCP795_REG_SECONDS, data, 5);
186 if (ret)
187 return ret;
188
189 ret = mcp795_rtcc_write(dev, MCP795_REG_MONTH, &data[5], 2);
190 if (ret)
191 return ret;
192
193 /* Start back RTC and restore previous value of EXTOSC bit.
194 * There is no need to clear EXTOSC bit when the previous value was 0
195 * because it was already cleared when stopping the RTC oscillator.
196 */
197 ret = mcp795_start_oscillator(dev, extosc ? &extosc : NULL);
198 if (ret)
199 return ret;
200
201 dev_dbg(dev, "Set mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
202 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
203 tim->tm_hour, tim->tm_min, tim->tm_sec);
204
205 return 0;
206}
207
208static int mcp795_read_time(struct device *dev, struct rtc_time *tim)
209{
210 int ret;
211 u8 data[7];
212
213 ret = mcp795_rtcc_read(dev, MCP795_REG_SECONDS, data, sizeof(data));
214
215 if (ret)
216 return ret;
217
218 tim->tm_sec = bcd2bin(data[0] & 0x7F);
219 tim->tm_min = bcd2bin(data[1] & 0x7F);
220 tim->tm_hour = bcd2bin(data[2] & 0x3F);
221 tim->tm_mday = bcd2bin(data[4] & 0x3F);
222 tim->tm_mon = bcd2bin(data[5] & 0x1F) - 1;
223 tim->tm_year = bcd2bin(data[6]) + 100; /* Assume we are in 20xx */
224
225 dev_dbg(dev, "Read from mcp795: %04d-%02d-%02d %02d:%02d:%02d\n",
226 tim->tm_year + 1900, tim->tm_mon, tim->tm_mday,
227 tim->tm_hour, tim->tm_min, tim->tm_sec);
228
229 return rtc_valid_tm(tim);
230}
231
232static const struct rtc_class_ops mcp795_rtc_ops = {
233 .read_time = mcp795_read_time,
234 .set_time = mcp795_set_time
235};
236
237static int mcp795_probe(struct spi_device *spi)
238{
239 struct rtc_device *rtc;
240 int ret;
241
242 spi->mode = SPI_MODE_0;
243 spi->bits_per_word = 8;
244 ret = spi_setup(spi);
245 if (ret) {
246 dev_err(&spi->dev, "Unable to setup SPI\n");
247 return ret;
248 }
249
250 /* Start the oscillator but don't set the value of EXTOSC bit */
251 mcp795_start_oscillator(&spi->dev, NULL);
252 /* Clear the 12 hour mode flag*/
253 mcp795_rtcc_set_bits(&spi->dev, 0x03, MCP795_24_BIT, 0);
254
255 rtc = devm_rtc_device_register(&spi->dev, "rtc-mcp795",
256 &mcp795_rtc_ops, THIS_MODULE);
257 if (IS_ERR(rtc))
258 return PTR_ERR(rtc);
259
260 spi_set_drvdata(spi, rtc);
261
262 return 0;
263}
264
265#ifdef CONFIG_OF
266static const struct of_device_id mcp795_of_match[] = {
267 { .compatible = "maxim,mcp795" },
268 { }
269};
270MODULE_DEVICE_TABLE(of, mcp795_of_match);
271#endif
272
273static struct spi_driver mcp795_driver = {
274 .driver = {
275 .name = "rtc-mcp795",
276 .of_match_table = of_match_ptr(mcp795_of_match),
277 },
278 .probe = mcp795_probe,
279};
280
281module_spi_driver(mcp795_driver);
282
283MODULE_DESCRIPTION("MCP795 RTC SPI Driver");
284MODULE_AUTHOR("Josef Gajdusek <atx@atx.name>");
285MODULE_LICENSE("GPL");
286MODULE_ALIAS("spi:mcp795");