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