Linux kernel mirror (for testing)
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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/arch/alpha/kernel/rtc.c
4 *
5 * Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds
6 *
7 * This file contains date handling.
8 */
9#include <linux/errno.h>
10#include <linux/init.h>
11#include <linux/kernel.h>
12#include <linux/param.h>
13#include <linux/string.h>
14#include <linux/mc146818rtc.h>
15#include <linux/bcd.h>
16#include <linux/rtc.h>
17#include <linux/platform_device.h>
18
19#include "proto.h"
20
21
22/*
23 * Support for the RTC device.
24 *
25 * We don't want to use the rtc-cmos driver, because we don't want to support
26 * alarms, as that would be indistinguishable from timer interrupts.
27 *
28 * Further, generic code is really, really tied to a 1900 epoch. This is
29 * true in __get_rtc_time as well as the users of struct rtc_time e.g.
30 * rtc_tm_to_time. Thankfully all of the other epochs in use are later
31 * than 1900, and so it's easy to adjust.
32 */
33
34static unsigned long rtc_epoch;
35
36static int __init
37specifiy_epoch(char *str)
38{
39 unsigned long epoch = simple_strtoul(str, NULL, 0);
40 if (epoch < 1900)
41 printk("Ignoring invalid user specified epoch %lu\n", epoch);
42 else
43 rtc_epoch = epoch;
44 return 1;
45}
46__setup("epoch=", specifiy_epoch);
47
48static void __init
49init_rtc_epoch(void)
50{
51 int epoch, year, ctrl;
52
53 if (rtc_epoch != 0) {
54 /* The epoch was specified on the command-line. */
55 return;
56 }
57
58 /* Detect the epoch in use on this computer. */
59 ctrl = CMOS_READ(RTC_CONTROL);
60 year = CMOS_READ(RTC_YEAR);
61 if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
62 year = bcd2bin(year);
63
64 /* PC-like is standard; used for year >= 70 */
65 epoch = 1900;
66 if (year < 20) {
67 epoch = 2000;
68 } else if (year >= 20 && year < 48) {
69 /* NT epoch */
70 epoch = 1980;
71 } else if (year >= 48 && year < 70) {
72 /* Digital UNIX epoch */
73 epoch = 1952;
74 }
75 rtc_epoch = epoch;
76
77 printk(KERN_INFO "Using epoch %d for rtc year %d\n", epoch, year);
78}
79
80static int
81alpha_rtc_read_time(struct device *dev, struct rtc_time *tm)
82{
83 mc146818_get_time(tm);
84
85 /* Adjust for non-default epochs. It's easier to depend on the
86 generic __get_rtc_time and adjust the epoch here than create
87 a copy of __get_rtc_time with the edits we need. */
88 if (rtc_epoch != 1900) {
89 int year = tm->tm_year;
90 /* Undo the century adjustment made in __get_rtc_time. */
91 if (year >= 100)
92 year -= 100;
93 year += rtc_epoch - 1900;
94 /* Redo the century adjustment with the epoch in place. */
95 if (year <= 69)
96 year += 100;
97 tm->tm_year = year;
98 }
99
100 return 0;
101}
102
103static int
104alpha_rtc_set_time(struct device *dev, struct rtc_time *tm)
105{
106 struct rtc_time xtm;
107
108 if (rtc_epoch != 1900) {
109 xtm = *tm;
110 xtm.tm_year -= rtc_epoch - 1900;
111 tm = &xtm;
112 }
113
114 return mc146818_set_time(tm);
115}
116
117static int
118alpha_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
119{
120 switch (cmd) {
121 case RTC_EPOCH_READ:
122 return put_user(rtc_epoch, (unsigned long __user *)arg);
123 case RTC_EPOCH_SET:
124 if (arg < 1900)
125 return -EINVAL;
126 rtc_epoch = arg;
127 return 0;
128 default:
129 return -ENOIOCTLCMD;
130 }
131}
132
133static const struct rtc_class_ops alpha_rtc_ops = {
134 .read_time = alpha_rtc_read_time,
135 .set_time = alpha_rtc_set_time,
136 .ioctl = alpha_rtc_ioctl,
137};
138
139/*
140 * Similarly, except do the actual CMOS access on the boot cpu only.
141 * This requires marshalling the data across an interprocessor call.
142 */
143
144#if defined(CONFIG_SMP) && \
145 (defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_MARVEL))
146# define HAVE_REMOTE_RTC 1
147
148union remote_data {
149 struct rtc_time *tm;
150 long retval;
151};
152
153static void
154do_remote_read(void *data)
155{
156 union remote_data *x = data;
157 x->retval = alpha_rtc_read_time(NULL, x->tm);
158}
159
160static int
161remote_read_time(struct device *dev, struct rtc_time *tm)
162{
163 union remote_data x;
164 if (smp_processor_id() != boot_cpuid) {
165 x.tm = tm;
166 smp_call_function_single(boot_cpuid, do_remote_read, &x, 1);
167 return x.retval;
168 }
169 return alpha_rtc_read_time(NULL, tm);
170}
171
172static void
173do_remote_set(void *data)
174{
175 union remote_data *x = data;
176 x->retval = alpha_rtc_set_time(NULL, x->tm);
177}
178
179static int
180remote_set_time(struct device *dev, struct rtc_time *tm)
181{
182 union remote_data x;
183 if (smp_processor_id() != boot_cpuid) {
184 x.tm = tm;
185 smp_call_function_single(boot_cpuid, do_remote_set, &x, 1);
186 return x.retval;
187 }
188 return alpha_rtc_set_time(NULL, tm);
189}
190
191static const struct rtc_class_ops remote_rtc_ops = {
192 .read_time = remote_read_time,
193 .set_time = remote_set_time,
194 .ioctl = alpha_rtc_ioctl,
195};
196#endif
197
198static int __init
199alpha_rtc_init(void)
200{
201 struct platform_device *pdev;
202 struct rtc_device *rtc;
203
204 init_rtc_epoch();
205
206 pdev = platform_device_register_simple("rtc-alpha", -1, NULL, 0);
207 rtc = devm_rtc_allocate_device(&pdev->dev);
208 if (IS_ERR(rtc))
209 return PTR_ERR(rtc);
210
211 platform_set_drvdata(pdev, rtc);
212 rtc->ops = &alpha_rtc_ops;
213
214#ifdef HAVE_REMOTE_RTC
215 if (alpha_mv.rtc_boot_cpu_only)
216 rtc->ops = &remote_rtc_ops;
217#endif
218
219 return devm_rtc_register_device(rtc);
220}
221device_initcall(alpha_rtc_init);