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147 lines · 3.3 KiB

1// SPDX-License-Identifier: GPL-2.0
2/*
3 * RTC related functions
4 */
5#include <linux/acpi.h>
6#include <linux/platform_device.h>
7#include <linux/mc146818rtc.h>
8#include <linux/export.h>
9
10#include <asm/vsyscall.h>
11#include <asm/x86_init.h>
12#include <asm/time.h>
13#include <asm/setup.h>
14
15#ifdef CONFIG_X86_32
16/*
17 * This is a special lock that is owned by the CPU and holds the index
18 * register we are working with. It is required for NMI access to the
19 * CMOS/RTC registers. See arch/x86/include/asm/mc146818rtc.h for details.
20 */
21volatile unsigned long cmos_lock;
22EXPORT_SYMBOL(cmos_lock);
23#endif /* CONFIG_X86_32 */
24
25DEFINE_SPINLOCK(rtc_lock);
26EXPORT_SYMBOL(rtc_lock);
27
28/*
29 * In order to set the CMOS clock precisely, mach_set_cmos_time has to be
30 * called 500 ms after the second nowtime has started, because when
31 * nowtime is written into the registers of the CMOS clock, it will
32 * jump to the next second precisely 500 ms later. Check the Motorola
33 * MC146818A or Dallas DS12887 data sheet for details.
34 */
35int mach_set_cmos_time(const struct timespec64 *now)
36{
37 unsigned long long nowtime = now->tv_sec;
38 struct rtc_time tm;
39 int retval = 0;
40
41 rtc_time64_to_tm(nowtime, &tm);
42 if (!rtc_valid_tm(&tm)) {
43 retval = mc146818_set_time(&tm);
44 if (retval)
45 printk(KERN_ERR "%s: RTC write failed with error %d\n",
46 __func__, retval);
47 } else {
48 printk(KERN_ERR
49 "%s: Invalid RTC value: write of %llx to RTC failed\n",
50 __func__, nowtime);
51 retval = -EINVAL;
52 }
53 return retval;
54}
55
56void mach_get_cmos_time(struct timespec64 *now)
57{
58 struct rtc_time tm;
59
60 /*
61 * If pm_trace abused the RTC as storage, set the timespec to 0,
62 * which tells the caller that this RTC value is unusable.
63 */
64 if (!pm_trace_rtc_valid()) {
65 now->tv_sec = now->tv_nsec = 0;
66 return;
67 }
68
69 if (mc146818_get_time(&tm, 1000)) {
70 pr_err("Unable to read current time from RTC\n");
71 now->tv_sec = now->tv_nsec = 0;
72 return;
73 }
74
75 now->tv_sec = rtc_tm_to_time64(&tm);
76 now->tv_nsec = 0;
77}
78
79/* Routines for accessing the CMOS RAM/RTC. */
80unsigned char rtc_cmos_read(unsigned char addr)
81{
82 unsigned char val;
83
84 lock_cmos_prefix(addr);
85 outb(addr, RTC_PORT(0));
86 val = inb(RTC_PORT(1));
87 lock_cmos_suffix(addr);
88
89 return val;
90}
91EXPORT_SYMBOL(rtc_cmos_read);
92
93void rtc_cmos_write(unsigned char val, unsigned char addr)
94{
95 lock_cmos_prefix(addr);
96 outb(addr, RTC_PORT(0));
97 outb(val, RTC_PORT(1));
98 lock_cmos_suffix(addr);
99}
100EXPORT_SYMBOL(rtc_cmos_write);
101
102int update_persistent_clock64(struct timespec64 now)
103{
104 return x86_platform.set_wallclock(&now);
105}
106
107/* not static: needed by APM */
108void read_persistent_clock64(struct timespec64 *ts)
109{
110 x86_platform.get_wallclock(ts);
111}
112
113
114static struct resource rtc_resources[] = {
115 [0] = {
116 .start = RTC_PORT(0),
117 .end = RTC_PORT(1),
118 .flags = IORESOURCE_IO,
119 },
120 [1] = {
121 .start = RTC_IRQ,
122 .end = RTC_IRQ,
123 .flags = IORESOURCE_IRQ,
124 }
125};
126
127static struct platform_device rtc_device = {
128 .name = "rtc_cmos",
129 .id = -1,
130 .resource = rtc_resources,
131 .num_resources = ARRAY_SIZE(rtc_resources),
132};
133
134static __init int add_rtc_cmos(void)
135{
136 if (cmos_rtc_platform_device_present)
137 return 0;
138
139 if (!x86_platform.legacy.rtc)
140 return -ENODEV;
141
142 platform_device_register(&rtc_device);
143 dev_info(&rtc_device.dev, "registered fallback platform RTC device\n");
144
145 return 0;
146}
147device_initcall(add_rtc_cmos);