2 * An rtc driver for the Dallas DS1742
4 * Copyright (C) 2006 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
10 * Copyright (C) 2006 Torsten Ertbjerg Rasmussen <tr@newtec.dk>
11 * - nvram size determined from resource
12 * - this ds1742 driver now supports ds1743.
15 #include <linux/bcd.h>
16 #include <linux/kernel.h>
17 #include <linux/gfp.h>
18 #include <linux/delay.h>
19 #include <linux/jiffies.h>
20 #include <linux/rtc.h>
22 #include <linux/of_device.h>
23 #include <linux/platform_device.h>
25 #include <linux/module.h>
39 #define RTC_CENTURY_MASK 0x3f
40 #define RTC_SECONDS_MASK 0x7f
41 #define RTC_DAY_MASK 0x07
43 /* Bits in the Control/Century register */
44 #define RTC_WRITE 0x80
47 /* Bits in the Seconds register */
50 /* Bits in the Day register */
51 #define RTC_BATT_FLAG 0x80
53 struct rtc_plat_data {
54 void __iomem *ioaddr_nvram;
55 void __iomem *ioaddr_rtc;
56 unsigned long last_jiffies;
59 static int ds1742_rtc_set_time(struct device *dev, struct rtc_time *tm)
61 struct platform_device *pdev = to_platform_device(dev);
62 struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
63 void __iomem *ioaddr = pdata->ioaddr_rtc;
66 century = bin2bcd((tm->tm_year + 1900) / 100);
68 writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
70 writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
71 writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
72 writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
73 writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
74 writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
75 writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
76 writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
78 /* RTC_CENTURY and RTC_CONTROL share same register */
79 writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
80 writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
84 static int ds1742_rtc_read_time(struct device *dev, struct rtc_time *tm)
86 struct platform_device *pdev = to_platform_device(dev);
87 struct rtc_plat_data *pdata = platform_get_drvdata(pdev);
88 void __iomem *ioaddr = pdata->ioaddr_rtc;
89 unsigned int year, month, day, hour, minute, second, week;
92 /* give enough time to update RTC in case of continuous read */
93 if (pdata->last_jiffies == jiffies)
95 pdata->last_jiffies = jiffies;
96 writeb(RTC_READ, ioaddr + RTC_CONTROL);
97 second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
98 minute = readb(ioaddr + RTC_MINUTES);
99 hour = readb(ioaddr + RTC_HOURS);
100 day = readb(ioaddr + RTC_DATE);
101 week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
102 month = readb(ioaddr + RTC_MONTH);
103 year = readb(ioaddr + RTC_YEAR);
104 century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
105 writeb(0, ioaddr + RTC_CONTROL);
106 tm->tm_sec = bcd2bin(second);
107 tm->tm_min = bcd2bin(minute);
108 tm->tm_hour = bcd2bin(hour);
109 tm->tm_mday = bcd2bin(day);
110 tm->tm_wday = bcd2bin(week);
111 tm->tm_mon = bcd2bin(month) - 1;
112 /* year is 1900 + tm->tm_year */
113 tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;
118 static const struct rtc_class_ops ds1742_rtc_ops = {
119 .read_time = ds1742_rtc_read_time,
120 .set_time = ds1742_rtc_set_time,
123 static int ds1742_nvram_read(void *priv, unsigned int pos, void *val,
126 struct rtc_plat_data *pdata = priv;
127 void __iomem *ioaddr = pdata->ioaddr_nvram;
130 for (; bytes; bytes--)
131 *buf++ = readb(ioaddr + pos++);
135 static int ds1742_nvram_write(void *priv, unsigned int pos, void *val,
138 struct rtc_plat_data *pdata = priv;
139 void __iomem *ioaddr = pdata->ioaddr_nvram;
142 for (; bytes; bytes--)
143 writeb(*buf++, ioaddr + pos++);
147 static int ds1742_rtc_probe(struct platform_device *pdev)
149 struct rtc_device *rtc;
150 struct resource *res;
151 unsigned int cen, sec;
152 struct rtc_plat_data *pdata;
153 void __iomem *ioaddr;
155 struct nvmem_config nvmem_cfg = {
156 .name = "ds1742_nvram",
159 .reg_read = ds1742_nvram_read,
160 .reg_write = ds1742_nvram_write,
164 pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
168 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
169 ioaddr = devm_ioremap_resource(&pdev->dev, res);
171 return PTR_ERR(ioaddr);
173 pdata->ioaddr_nvram = ioaddr;
174 pdata->ioaddr_rtc = ioaddr + resource_size(res) - RTC_SIZE;
176 nvmem_cfg.size = resource_size(res) - RTC_SIZE;
177 nvmem_cfg.priv = pdata;
179 /* turn RTC on if it was not on */
180 ioaddr = pdata->ioaddr_rtc;
181 sec = readb(ioaddr + RTC_SECONDS);
182 if (sec & RTC_STOP) {
183 sec &= RTC_SECONDS_MASK;
184 cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
185 writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
186 writeb(sec, ioaddr + RTC_SECONDS);
187 writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
189 if (!(readb(ioaddr + RTC_DAY) & RTC_BATT_FLAG))
190 dev_warn(&pdev->dev, "voltage-low detected.\n");
192 pdata->last_jiffies = jiffies;
193 platform_set_drvdata(pdev, pdata);
195 rtc = devm_rtc_allocate_device(&pdev->dev);
199 rtc->ops = &ds1742_rtc_ops;
200 rtc->nvram_old_abi = true;
202 ret = rtc_register_device(rtc);
206 if (rtc_nvmem_register(rtc, &nvmem_cfg))
207 dev_err(&pdev->dev, "Unable to register nvmem\n");
212 static const struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
213 { .compatible = "maxim,ds1742", },
216 MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);
218 static struct platform_driver ds1742_rtc_driver = {
219 .probe = ds1742_rtc_probe,
221 .name = "rtc-ds1742",
222 .of_match_table = of_match_ptr(ds1742_rtc_of_match),
226 module_platform_driver(ds1742_rtc_driver);
228 MODULE_AUTHOR("Atsushi Nemoto <anemo@mba.ocn.ne.jp>");
229 MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
230 MODULE_LICENSE("GPL");
231 MODULE_ALIAS("platform:rtc-ds1742");