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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * An rtc driver for the Dallas DS1742
4 *
5 * Copyright (C) 2006 Atsushi Nemoto <[email protected]>
6 *
7 * Copyright (C) 2006 Torsten Ertbjerg Rasmussen <[email protected]>
8 * - nvram size determined from resource
9 * - this ds1742 driver now supports ds1743.
10 */
11
12#include <linux/bcd.h>
13#include <linux/kernel.h>
14#include <linux/gfp.h>
15#include <linux/delay.h>
16#include <linux/jiffies.h>
17#include <linux/rtc.h>
18#include <linux/of.h>
19#include <linux/platform_device.h>
20#include <linux/io.h>
21#include <linux/module.h>
22
23#define RTC_SIZE 8
24
25#define RTC_CONTROL 0
26#define RTC_CENTURY 0
27#define RTC_SECONDS 1
28#define RTC_MINUTES 2
29#define RTC_HOURS 3
30#define RTC_DAY 4
31#define RTC_DATE 5
32#define RTC_MONTH 6
33#define RTC_YEAR 7
34
35#define RTC_CENTURY_MASK 0x3f
36#define RTC_SECONDS_MASK 0x7f
37#define RTC_DAY_MASK 0x07
38
39/* Bits in the Control/Century register */
40#define RTC_WRITE 0x80
41#define RTC_READ 0x40
42
43/* Bits in the Seconds register */
44#define RTC_STOP 0x80
45
46/* Bits in the Day register */
47#define RTC_BATT_FLAG 0x80
48
49struct rtc_plat_data {
50 void __iomem *ioaddr_nvram;
51 void __iomem *ioaddr_rtc;
52 unsigned long last_jiffies;
53};
54
55static int ds1742_rtc_set_time(struct device *dev, struct rtc_time *tm)
56{
57 struct rtc_plat_data *pdata = dev_get_drvdata(dev);
58 void __iomem *ioaddr = pdata->ioaddr_rtc;
59 u8 century;
60
61 century = bin2bcd((tm->tm_year + 1900) / 100);
62
63 writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
64
65 writeb(bin2bcd(tm->tm_year % 100), ioaddr + RTC_YEAR);
66 writeb(bin2bcd(tm->tm_mon + 1), ioaddr + RTC_MONTH);
67 writeb(bin2bcd(tm->tm_wday) & RTC_DAY_MASK, ioaddr + RTC_DAY);
68 writeb(bin2bcd(tm->tm_mday), ioaddr + RTC_DATE);
69 writeb(bin2bcd(tm->tm_hour), ioaddr + RTC_HOURS);
70 writeb(bin2bcd(tm->tm_min), ioaddr + RTC_MINUTES);
71 writeb(bin2bcd(tm->tm_sec) & RTC_SECONDS_MASK, ioaddr + RTC_SECONDS);
72
73 /* RTC_CENTURY and RTC_CONTROL share same register */
74 writeb(RTC_WRITE | (century & RTC_CENTURY_MASK), ioaddr + RTC_CENTURY);
75 writeb(century & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
76 return 0;
77}
78
79static int ds1742_rtc_read_time(struct device *dev, struct rtc_time *tm)
80{
81 struct rtc_plat_data *pdata = dev_get_drvdata(dev);
82 void __iomem *ioaddr = pdata->ioaddr_rtc;
83 unsigned int year, month, day, hour, minute, second, week;
84 unsigned int century;
85
86 /* give enough time to update RTC in case of continuous read */
87 if (pdata->last_jiffies == jiffies)
88 msleep(1);
89 pdata->last_jiffies = jiffies;
90 writeb(RTC_READ, ioaddr + RTC_CONTROL);
91 second = readb(ioaddr + RTC_SECONDS) & RTC_SECONDS_MASK;
92 minute = readb(ioaddr + RTC_MINUTES);
93 hour = readb(ioaddr + RTC_HOURS);
94 day = readb(ioaddr + RTC_DATE);
95 week = readb(ioaddr + RTC_DAY) & RTC_DAY_MASK;
96 month = readb(ioaddr + RTC_MONTH);
97 year = readb(ioaddr + RTC_YEAR);
98 century = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
99 writeb(0, ioaddr + RTC_CONTROL);
100 tm->tm_sec = bcd2bin(second);
101 tm->tm_min = bcd2bin(minute);
102 tm->tm_hour = bcd2bin(hour);
103 tm->tm_mday = bcd2bin(day);
104 tm->tm_wday = bcd2bin(week);
105 tm->tm_mon = bcd2bin(month) - 1;
106 /* year is 1900 + tm->tm_year */
107 tm->tm_year = bcd2bin(year) + bcd2bin(century) * 100 - 1900;
108
109 return 0;
110}
111
112static const struct rtc_class_ops ds1742_rtc_ops = {
113 .read_time = ds1742_rtc_read_time,
114 .set_time = ds1742_rtc_set_time,
115};
116
117static int ds1742_nvram_read(void *priv, unsigned int pos, void *val,
118 size_t bytes)
119{
120 struct rtc_plat_data *pdata = priv;
121 void __iomem *ioaddr = pdata->ioaddr_nvram;
122 u8 *buf = val;
123
124 for (; bytes; bytes--)
125 *buf++ = readb(ioaddr + pos++);
126 return 0;
127}
128
129static int ds1742_nvram_write(void *priv, unsigned int pos, void *val,
130 size_t bytes)
131{
132 struct rtc_plat_data *pdata = priv;
133 void __iomem *ioaddr = pdata->ioaddr_nvram;
134 u8 *buf = val;
135
136 for (; bytes; bytes--)
137 writeb(*buf++, ioaddr + pos++);
138 return 0;
139}
140
141static int ds1742_rtc_probe(struct platform_device *pdev)
142{
143 struct rtc_device *rtc;
144 struct resource *res;
145 unsigned int cen, sec;
146 struct rtc_plat_data *pdata;
147 void __iomem *ioaddr;
148 int ret = 0;
149 struct nvmem_config nvmem_cfg = {
150 .name = "ds1742_nvram",
151 .reg_read = ds1742_nvram_read,
152 .reg_write = ds1742_nvram_write,
153 };
154
155
156 pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
157 if (!pdata)
158 return -ENOMEM;
159
160 ioaddr = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
161 if (IS_ERR(ioaddr))
162 return PTR_ERR(ioaddr);
163
164 pdata->ioaddr_nvram = ioaddr;
165 pdata->ioaddr_rtc = ioaddr + resource_size(res) - RTC_SIZE;
166
167 nvmem_cfg.size = resource_size(res) - RTC_SIZE;
168 nvmem_cfg.priv = pdata;
169
170 /* turn RTC on if it was not on */
171 ioaddr = pdata->ioaddr_rtc;
172 sec = readb(ioaddr + RTC_SECONDS);
173 if (sec & RTC_STOP) {
174 sec &= RTC_SECONDS_MASK;
175 cen = readb(ioaddr + RTC_CENTURY) & RTC_CENTURY_MASK;
176 writeb(RTC_WRITE, ioaddr + RTC_CONTROL);
177 writeb(sec, ioaddr + RTC_SECONDS);
178 writeb(cen & RTC_CENTURY_MASK, ioaddr + RTC_CONTROL);
179 }
180 if (!(readb(ioaddr + RTC_DAY) & RTC_BATT_FLAG))
181 dev_warn(&pdev->dev, "voltage-low detected.\n");
182
183 pdata->last_jiffies = jiffies;
184 platform_set_drvdata(pdev, pdata);
185
186 rtc = devm_rtc_allocate_device(&pdev->dev);
187 if (IS_ERR(rtc))
188 return PTR_ERR(rtc);
189
190 rtc->ops = &ds1742_rtc_ops;
191
192 ret = devm_rtc_register_device(rtc);
193 if (ret)
194 return ret;
195
196 devm_rtc_nvmem_register(rtc, &nvmem_cfg);
197
198 return 0;
199}
200
201static const struct of_device_id __maybe_unused ds1742_rtc_of_match[] = {
202 { .compatible = "maxim,ds1742", },
203 { }
204};
205MODULE_DEVICE_TABLE(of, ds1742_rtc_of_match);
206
207static struct platform_driver ds1742_rtc_driver = {
208 .probe = ds1742_rtc_probe,
209 .driver = {
210 .name = "rtc-ds1742",
211 .of_match_table = of_match_ptr(ds1742_rtc_of_match),
212 },
213};
214
215module_platform_driver(ds1742_rtc_driver);
216
217MODULE_AUTHOR("Atsushi Nemoto <[email protected]>");
218MODULE_DESCRIPTION("Dallas DS1742 RTC driver");
219MODULE_LICENSE("GPL");
220MODULE_ALIAS("platform:rtc-ds1742");