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	RTC_CMD_READ	0x81		/* Read command */
19#define	RTC_CMD_WRITE	0x80		/* Write command */
20
21#define	RTC_CMD_WRITE_ENABLE	0x00		/* Write enable */
22#define	RTC_CMD_WRITE_DISABLE	0x80		/* Write disable */
23
24#define RTC_ADDR_RAM0	0x20		/* Address of RAM0 */
25#define RTC_ADDR_TCR	0x08		/* Address of trickle charge register */
26#define RTC_CLCK_BURST	0x1F		/* Address of clock burst */
27#define	RTC_CLCK_LEN	0x08		/* Size of clock burst */
28#define	RTC_ADDR_CTRL	0x07		/* Address of control register */
29#define	RTC_ADDR_YEAR	0x06		/* Address of year register */
30#define	RTC_ADDR_DAY	0x05		/* Address of day of week register */
31#define	RTC_ADDR_MON	0x04		/* Address of month register */
32#define	RTC_ADDR_DATE	0x03		/* Address of day of month register */
33#define	RTC_ADDR_HOUR	0x02		/* Address of hour register */
34#define	RTC_ADDR_MIN	0x01		/* Address of minute register */
35#define	RTC_ADDR_SEC	0x00		/* Address of second register */
36
37static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
38{
39	struct spi_device	*spi = dev_get_drvdata(dev);
40	u8		buf[1 + RTC_CLCK_LEN];
41	u8		*bp;
42	int		status;
43
44	/* Enable writing */
45	bp = buf;
46	*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
47	*bp++ = RTC_CMD_WRITE_ENABLE;
48
49	status = spi_write_then_read(spi, buf, 2,
50			NULL, 0);
51	if (status)
52		return status;
53
54	/* Write registers starting at the first time/date address. */
55	bp = buf;
56	*bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
57
58	*bp++ = bin2bcd(time->tm_sec);
59	*bp++ = bin2bcd(time->tm_min);
60	*bp++ = bin2bcd(time->tm_hour);
61	*bp++ = bin2bcd(time->tm_mday);
62	*bp++ = bin2bcd(time->tm_mon + 1);
63	*bp++ = time->tm_wday + 1;
64	*bp++ = bin2bcd(time->tm_year % 100);
65	*bp++ = RTC_CMD_WRITE_DISABLE;
66
67	/* use write-then-read since dma from stack is nonportable */
68	return spi_write_then_read(spi, buf, sizeof(buf),
69			NULL, 0);
70}
71
72static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
73{
74	struct spi_device	*spi = dev_get_drvdata(dev);
75	u8		addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
76	u8		buf[RTC_CLCK_LEN - 1];
77	int		status;
78
79	/* Use write-then-read to get all the date/time registers
80	 * since dma from stack is nonportable
81	 */
82	status = spi_write_then_read(spi, &addr, sizeof(addr),
83			buf, sizeof(buf));
84	if (status < 0)
85		return status;
86
87	/* Decode the registers */
88	time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
89	time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
90	time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
91	time->tm_wday = buf[RTC_ADDR_DAY] - 1;
92	time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
93	time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
94	time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
95
96	return 0;
97}
98
99static const struct rtc_class_ops ds1302_rtc_ops = {
100	.read_time	= ds1302_rtc_get_time,
101	.set_time	= ds1302_rtc_set_time,
102};
103
104static int ds1302_probe(struct spi_device *spi)
105{
106	struct rtc_device	*rtc;
107	u8		addr;
108	u8		buf[4];
109	u8		*bp;
110	int		status;
111
112	/* Sanity check board setup data.  This may be hooked up
113	 * in 3wire mode, but we don't care.  Note that unless
114	 * there's an inverter in place, this needs SPI_CS_HIGH!
115	 */
116	if (spi->bits_per_word && (spi->bits_per_word != 8)) {
117		dev_err(&spi->dev, "bad word length\n");
118		return -EINVAL;
119	} else if (spi->max_speed_hz > 2000000) {
120		dev_err(&spi->dev, "speed is too high\n");
121		return -EINVAL;
122	} else if (spi->mode & SPI_CPHA) {
123		dev_err(&spi->dev, "bad mode\n");
124		return -EINVAL;
125	}
126
127	addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
128	status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
129	if (status < 0) {
130		dev_err(&spi->dev, "control register read error %d\n",
131				status);
132		return status;
133	}
134
135	if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
136		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
137		if (status < 0) {
138			dev_err(&spi->dev, "control register read error %d\n",
139					status);
140			return status;
141		}
142
143		if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
144			dev_err(&spi->dev, "junk in control register\n");
145			return -ENODEV;
146		}
147	}
148	if (buf[0] == 0) {
149		bp = buf;
150		*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
151		*bp++ = RTC_CMD_WRITE_DISABLE;
152
153		status = spi_write_then_read(spi, buf, 2, NULL, 0);
154		if (status < 0) {
155			dev_err(&spi->dev, "control register write error %d\n",
156					status);
157			return status;
158		}
159
160		addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
161		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
162		if (status < 0) {
163			dev_err(&spi->dev,
164					"error %d reading control register\n",
165					status);
166			return status;
167		}
168
169		if (buf[0] != RTC_CMD_WRITE_DISABLE) {
170			dev_err(&spi->dev, "failed to detect chip\n");
171			return -ENODEV;
172		}
173	}
174
175	spi_set_drvdata(spi, spi);
176
177	rtc = devm_rtc_device_register(&spi->dev, "ds1302",
178			&ds1302_rtc_ops, THIS_MODULE);
179	if (IS_ERR(rtc)) {
180		status = PTR_ERR(rtc);
181		dev_err(&spi->dev, "error %d registering rtc\n", status);
182		return status;
183	}
184
185	return 0;
186}
187
188#ifdef CONFIG_OF
189static const struct of_device_id ds1302_dt_ids[] = {
190	{ .compatible = "maxim,ds1302", },
191	{ /* sentinel */ }
192};
193MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
194#endif
195
196static const struct spi_device_id ds1302_spi_ids[] = {
197	{ .name = "ds1302", },
198	{ /* sentinel */ }
199};
200MODULE_DEVICE_TABLE(spi, ds1302_spi_ids);
201
202static struct spi_driver ds1302_driver = {
203	.driver.name	= "rtc-ds1302",
204	.driver.of_match_table = of_match_ptr(ds1302_dt_ids),
205	.probe		= ds1302_probe,
206	.id_table	= ds1302_spi_ids,
207};
208
209module_spi_driver(ds1302_driver);
210
211MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
212MODULE_AUTHOR("Paul Mundt, David McCullough");
213MODULE_LICENSE("GPL v2");
214