1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Dallas DS1302 RTC Support
4 *
5 * Copyright (C) 2002 David McCullough
6 * Copyright (C) 2003 - 2007 Paul Mundt
7 */
8
9 #include <linux/bcd.h>
10 #include <linux/init.h>
11 #include <linux/io.h>
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/rtc.h>
16 #include <linux/spi/spi.h>
17
18 #define DRV_NAME "rtc-ds1302"
19
20 #define RTC_CMD_READ 0x81 /* Read command */
21 #define RTC_CMD_WRITE 0x80 /* Write command */
22
23 #define RTC_CMD_WRITE_ENABLE 0x00 /* Write enable */
24 #define RTC_CMD_WRITE_DISABLE 0x80 /* Write disable */
25
26 #define RTC_ADDR_RAM0 0x20 /* Address of RAM0 */
27 #define RTC_ADDR_TCR 0x08 /* Address of trickle charge register */
28 #define RTC_CLCK_BURST 0x1F /* Address of clock burst */
29 #define RTC_CLCK_LEN 0x08 /* Size of clock burst */
30 #define RTC_ADDR_CTRL 0x07 /* Address of control register */
31 #define RTC_ADDR_YEAR 0x06 /* Address of year register */
32 #define RTC_ADDR_DAY 0x05 /* Address of day of week register */
33 #define RTC_ADDR_MON 0x04 /* Address of month register */
34 #define RTC_ADDR_DATE 0x03 /* Address of day of month register */
35 #define RTC_ADDR_HOUR 0x02 /* Address of hour register */
36 #define RTC_ADDR_MIN 0x01 /* Address of minute register */
37 #define RTC_ADDR_SEC 0x00 /* Address of second register */
38
ds1302_rtc_set_time(struct device * dev,struct rtc_time * time)39 static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
40 {
41 struct spi_device *spi = dev_get_drvdata(dev);
42 u8 buf[1 + RTC_CLCK_LEN];
43 u8 *bp;
44 int status;
45
46 /* Enable writing */
47 bp = buf;
48 *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
49 *bp++ = RTC_CMD_WRITE_ENABLE;
50
51 status = spi_write_then_read(spi, buf, 2,
52 NULL, 0);
53 if (status)
54 return status;
55
56 /* Write registers starting at the first time/date address. */
57 bp = buf;
58 *bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
59
60 *bp++ = bin2bcd(time->tm_sec);
61 *bp++ = bin2bcd(time->tm_min);
62 *bp++ = bin2bcd(time->tm_hour);
63 *bp++ = bin2bcd(time->tm_mday);
64 *bp++ = bin2bcd(time->tm_mon + 1);
65 *bp++ = time->tm_wday + 1;
66 *bp++ = bin2bcd(time->tm_year % 100);
67 *bp++ = RTC_CMD_WRITE_DISABLE;
68
69 /* use write-then-read since dma from stack is nonportable */
70 return spi_write_then_read(spi, buf, sizeof(buf),
71 NULL, 0);
72 }
73
ds1302_rtc_get_time(struct device * dev,struct rtc_time * time)74 static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
75 {
76 struct spi_device *spi = dev_get_drvdata(dev);
77 u8 addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
78 u8 buf[RTC_CLCK_LEN - 1];
79 int status;
80
81 /* Use write-then-read to get all the date/time registers
82 * since dma from stack is nonportable
83 */
84 status = spi_write_then_read(spi, &addr, sizeof(addr),
85 buf, sizeof(buf));
86 if (status < 0)
87 return status;
88
89 /* Decode the registers */
90 time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
91 time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
92 time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
93 time->tm_wday = buf[RTC_ADDR_DAY] - 1;
94 time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
95 time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
96 time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
97
98 return 0;
99 }
100
101 static const struct rtc_class_ops ds1302_rtc_ops = {
102 .read_time = ds1302_rtc_get_time,
103 .set_time = ds1302_rtc_set_time,
104 };
105
ds1302_probe(struct spi_device * spi)106 static int ds1302_probe(struct spi_device *spi)
107 {
108 struct rtc_device *rtc;
109 u8 addr;
110 u8 buf[4];
111 u8 *bp;
112 int status;
113
114 /* Sanity check board setup data. This may be hooked up
115 * in 3wire mode, but we don't care. Note that unless
116 * there's an inverter in place, this needs SPI_CS_HIGH!
117 */
118 if (spi->bits_per_word && (spi->bits_per_word != 8)) {
119 dev_err(&spi->dev, "bad word length\n");
120 return -EINVAL;
121 } else if (spi->max_speed_hz > 2000000) {
122 dev_err(&spi->dev, "speed is too high\n");
123 return -EINVAL;
124 } else if (spi->mode & SPI_CPHA) {
125 dev_err(&spi->dev, "bad mode\n");
126 return -EINVAL;
127 }
128
129 addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
130 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
131 if (status < 0) {
132 dev_err(&spi->dev, "control register read error %d\n",
133 status);
134 return status;
135 }
136
137 if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
138 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
139 if (status < 0) {
140 dev_err(&spi->dev, "control register read error %d\n",
141 status);
142 return status;
143 }
144
145 if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
146 dev_err(&spi->dev, "junk in control register\n");
147 return -ENODEV;
148 }
149 }
150 if (buf[0] == 0) {
151 bp = buf;
152 *bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
153 *bp++ = RTC_CMD_WRITE_DISABLE;
154
155 status = spi_write_then_read(spi, buf, 2, NULL, 0);
156 if (status < 0) {
157 dev_err(&spi->dev, "control register write error %d\n",
158 status);
159 return status;
160 }
161
162 addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
163 status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
164 if (status < 0) {
165 dev_err(&spi->dev,
166 "error %d reading control register\n",
167 status);
168 return status;
169 }
170
171 if (buf[0] != RTC_CMD_WRITE_DISABLE) {
172 dev_err(&spi->dev, "failed to detect chip\n");
173 return -ENODEV;
174 }
175 }
176
177 spi_set_drvdata(spi, spi);
178
179 rtc = devm_rtc_device_register(&spi->dev, "ds1302",
180 &ds1302_rtc_ops, THIS_MODULE);
181 if (IS_ERR(rtc)) {
182 status = PTR_ERR(rtc);
183 dev_err(&spi->dev, "error %d registering rtc\n", status);
184 return status;
185 }
186
187 return 0;
188 }
189
ds1302_remove(struct spi_device * spi)190 static int ds1302_remove(struct spi_device *spi)
191 {
192 spi_set_drvdata(spi, NULL);
193 return 0;
194 }
195
196 #ifdef CONFIG_OF
197 static const struct of_device_id ds1302_dt_ids[] = {
198 { .compatible = "maxim,ds1302", },
199 { /* sentinel */ }
200 };
201 MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
202 #endif
203
204 static struct spi_driver ds1302_driver = {
205 .driver.name = "rtc-ds1302",
206 .driver.of_match_table = of_match_ptr(ds1302_dt_ids),
207 .probe = ds1302_probe,
208 .remove = ds1302_remove,
209 };
210
211 module_spi_driver(ds1302_driver);
212
213 MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
214 MODULE_AUTHOR("Paul Mundt, David McCullough");
215 MODULE_LICENSE("GPL v2");
216