xref: /openbmc/linux/drivers/rtc/rtc-ds1390.c (revision cca1e2f7)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * rtc-ds1390.c -- driver for the Dallas/Maxim DS1390/93/94 SPI RTC
4  *
5  * Copyright (C) 2008 Mercury IMC Ltd
6  * Written by Mark Jackson <mpfj@mimc.co.uk>
7  *
8  * NOTE: Currently this driver only supports the bare minimum for read
9  * and write the RTC. The extra features provided by the chip family
10  * (alarms, trickle charger, different control registers) are unavailable.
11  */
12 
13 #include <linux/init.h>
14 #include <linux/module.h>
15 #include <linux/platform_device.h>
16 #include <linux/rtc.h>
17 #include <linux/spi/spi.h>
18 #include <linux/bcd.h>
19 #include <linux/slab.h>
20 #include <linux/of.h>
21 
22 #define DS1390_REG_100THS		0x00
23 #define DS1390_REG_SECONDS		0x01
24 #define DS1390_REG_MINUTES		0x02
25 #define DS1390_REG_HOURS		0x03
26 #define DS1390_REG_DAY			0x04
27 #define DS1390_REG_DATE			0x05
28 #define DS1390_REG_MONTH_CENT		0x06
29 #define DS1390_REG_YEAR			0x07
30 
31 #define DS1390_REG_ALARM_100THS		0x08
32 #define DS1390_REG_ALARM_SECONDS	0x09
33 #define DS1390_REG_ALARM_MINUTES	0x0A
34 #define DS1390_REG_ALARM_HOURS		0x0B
35 #define DS1390_REG_ALARM_DAY_DATE	0x0C
36 
37 #define DS1390_REG_CONTROL		0x0D
38 #define DS1390_REG_STATUS		0x0E
39 #define DS1390_REG_TRICKLE		0x0F
40 
41 #define DS1390_TRICKLE_CHARGER_ENABLE	0xA0
42 #define DS1390_TRICKLE_CHARGER_250_OHM	0x01
43 #define DS1390_TRICKLE_CHARGER_2K_OHM	0x02
44 #define DS1390_TRICKLE_CHARGER_4K_OHM	0x03
45 #define DS1390_TRICKLE_CHARGER_NO_DIODE	0x04
46 #define DS1390_TRICKLE_CHARGER_DIODE	0x08
47 
48 struct ds1390 {
49 	struct rtc_device *rtc;
50 	u8 txrx_buf[9];	/* cmd + 8 registers */
51 };
52 
ds1390_set_reg(struct device * dev,unsigned char address,unsigned char data)53 static void ds1390_set_reg(struct device *dev, unsigned char address,
54 			   unsigned char data)
55 {
56 	struct spi_device *spi = to_spi_device(dev);
57 	unsigned char buf[2];
58 
59 	/* MSB must be '1' to write */
60 	buf[0] = address | 0x80;
61 	buf[1] = data;
62 
63 	spi_write(spi, buf, 2);
64 }
65 
ds1390_get_reg(struct device * dev,unsigned char address,unsigned char * data)66 static int ds1390_get_reg(struct device *dev, unsigned char address,
67 				unsigned char *data)
68 {
69 	struct spi_device *spi = to_spi_device(dev);
70 	struct ds1390 *chip = dev_get_drvdata(dev);
71 	int status;
72 
73 	if (!data)
74 		return -EINVAL;
75 
76 	/* Clear MSB to indicate read */
77 	chip->txrx_buf[0] = address & 0x7f;
78 	/* do the i/o */
79 	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 1);
80 	if (status != 0)
81 		return status;
82 
83 	*data = chip->txrx_buf[0];
84 
85 	return 0;
86 }
87 
ds1390_trickle_of_init(struct spi_device * spi)88 static void ds1390_trickle_of_init(struct spi_device *spi)
89 {
90 	u32 ohms = 0;
91 	u8 value;
92 
93 	if (of_property_read_u32(spi->dev.of_node, "trickle-resistor-ohms",
94 				 &ohms))
95 		goto out;
96 
97 	/* Enable charger */
98 	value = DS1390_TRICKLE_CHARGER_ENABLE;
99 	if (of_property_read_bool(spi->dev.of_node, "trickle-diode-disable"))
100 		value |= DS1390_TRICKLE_CHARGER_NO_DIODE;
101 	else
102 		value |= DS1390_TRICKLE_CHARGER_DIODE;
103 
104 	/* Resistor select */
105 	switch (ohms) {
106 	case 250:
107 		value |= DS1390_TRICKLE_CHARGER_250_OHM;
108 		break;
109 	case 2000:
110 		value |= DS1390_TRICKLE_CHARGER_2K_OHM;
111 		break;
112 	case 4000:
113 		value |= DS1390_TRICKLE_CHARGER_4K_OHM;
114 		break;
115 	default:
116 		dev_warn(&spi->dev,
117 			 "Unsupported ohm value %02ux in dt\n", ohms);
118 		return;
119 	}
120 
121 	ds1390_set_reg(&spi->dev, DS1390_REG_TRICKLE, value);
122 
123 out:
124 	return;
125 }
126 
ds1390_read_time(struct device * dev,struct rtc_time * dt)127 static int ds1390_read_time(struct device *dev, struct rtc_time *dt)
128 {
129 	struct spi_device *spi = to_spi_device(dev);
130 	struct ds1390 *chip = dev_get_drvdata(dev);
131 	int status;
132 
133 	/* build the message */
134 	chip->txrx_buf[0] = DS1390_REG_SECONDS;
135 
136 	/* do the i/o */
137 	status = spi_write_then_read(spi, chip->txrx_buf, 1, chip->txrx_buf, 8);
138 	if (status != 0)
139 		return status;
140 
141 	/* The chip sends data in this order:
142 	 * Seconds, Minutes, Hours, Day, Date, Month / Century, Year */
143 	dt->tm_sec	= bcd2bin(chip->txrx_buf[0]);
144 	dt->tm_min	= bcd2bin(chip->txrx_buf[1]);
145 	dt->tm_hour	= bcd2bin(chip->txrx_buf[2]);
146 	dt->tm_wday	= bcd2bin(chip->txrx_buf[3]);
147 	dt->tm_mday	= bcd2bin(chip->txrx_buf[4]);
148 	/* mask off century bit */
149 	dt->tm_mon	= bcd2bin(chip->txrx_buf[5] & 0x7f) - 1;
150 	/* adjust for century bit */
151 	dt->tm_year = bcd2bin(chip->txrx_buf[6]) + ((chip->txrx_buf[5] & 0x80) ? 100 : 0);
152 
153 	return 0;
154 }
155 
ds1390_set_time(struct device * dev,struct rtc_time * dt)156 static int ds1390_set_time(struct device *dev, struct rtc_time *dt)
157 {
158 	struct spi_device *spi = to_spi_device(dev);
159 	struct ds1390 *chip = dev_get_drvdata(dev);
160 
161 	/* build the message */
162 	chip->txrx_buf[0] = DS1390_REG_SECONDS | 0x80;
163 	chip->txrx_buf[1] = bin2bcd(dt->tm_sec);
164 	chip->txrx_buf[2] = bin2bcd(dt->tm_min);
165 	chip->txrx_buf[3] = bin2bcd(dt->tm_hour);
166 	chip->txrx_buf[4] = bin2bcd(dt->tm_wday);
167 	chip->txrx_buf[5] = bin2bcd(dt->tm_mday);
168 	chip->txrx_buf[6] = bin2bcd(dt->tm_mon + 1) |
169 				((dt->tm_year > 99) ? 0x80 : 0x00);
170 	chip->txrx_buf[7] = bin2bcd(dt->tm_year % 100);
171 
172 	/* do the i/o */
173 	return spi_write_then_read(spi, chip->txrx_buf, 8, NULL, 0);
174 }
175 
176 static const struct rtc_class_ops ds1390_rtc_ops = {
177 	.read_time	= ds1390_read_time,
178 	.set_time	= ds1390_set_time,
179 };
180 
ds1390_probe(struct spi_device * spi)181 static int ds1390_probe(struct spi_device *spi)
182 {
183 	unsigned char tmp;
184 	struct ds1390 *chip;
185 	int res;
186 
187 	spi->mode = SPI_MODE_3;
188 	spi->bits_per_word = 8;
189 	spi_setup(spi);
190 
191 	chip = devm_kzalloc(&spi->dev, sizeof(*chip), GFP_KERNEL);
192 	if (!chip)
193 		return -ENOMEM;
194 
195 	spi_set_drvdata(spi, chip);
196 
197 	res = ds1390_get_reg(&spi->dev, DS1390_REG_SECONDS, &tmp);
198 	if (res != 0) {
199 		dev_err(&spi->dev, "unable to read device\n");
200 		return res;
201 	}
202 
203 	if (spi->dev.of_node)
204 		ds1390_trickle_of_init(spi);
205 
206 	chip->rtc = devm_rtc_device_register(&spi->dev, "ds1390",
207 					&ds1390_rtc_ops, THIS_MODULE);
208 	if (IS_ERR(chip->rtc)) {
209 		dev_err(&spi->dev, "unable to register device\n");
210 		res = PTR_ERR(chip->rtc);
211 	}
212 
213 	return res;
214 }
215 
216 static const struct of_device_id ds1390_of_match[] __maybe_unused = {
217 	{ .compatible = "dallas,ds1390" },
218 	{}
219 };
220 MODULE_DEVICE_TABLE(of, ds1390_of_match);
221 
222 static const struct spi_device_id ds1390_spi_ids[] = {
223 	{ .name = "ds1390" },
224 	{}
225 };
226 MODULE_DEVICE_TABLE(spi, ds1390_spi_ids);
227 
228 static struct spi_driver ds1390_driver = {
229 	.driver = {
230 		.name	= "rtc-ds1390",
231 		.of_match_table = of_match_ptr(ds1390_of_match),
232 	},
233 	.probe	= ds1390_probe,
234 	.id_table = ds1390_spi_ids,
235 };
236 
237 module_spi_driver(ds1390_driver);
238 
239 MODULE_DESCRIPTION("Dallas/Maxim DS1390/93/94 SPI RTC driver");
240 MODULE_AUTHOR("Mark Jackson <mpfj@mimc.co.uk>");
241 MODULE_LICENSE("GPL");
242 MODULE_ALIAS("spi:rtc-ds1390");
243