xref: /openbmc/linux/arch/x86/kernel/rtc.c (revision 49a76c08)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * RTC related functions
4  */
5 #include <linux/platform_device.h>
6 #include <linux/mc146818rtc.h>
7 #include <linux/export.h>
8 #include <linux/pnp.h>
9 
10 #include <asm/vsyscall.h>
11 #include <asm/x86_init.h>
12 #include <asm/time.h>
13 #include <asm/intel-mid.h>
14 #include <asm/setup.h>
15 
16 #ifdef CONFIG_X86_32
17 /*
18  * This is a special lock that is owned by the CPU and holds the index
19  * register we are working with.  It is required for NMI access to the
20  * CMOS/RTC registers.  See arch/x86/include/asm/mc146818rtc.h for details.
21  */
22 volatile unsigned long cmos_lock;
23 EXPORT_SYMBOL(cmos_lock);
24 #endif /* CONFIG_X86_32 */
25 
26 DEFINE_SPINLOCK(rtc_lock);
27 EXPORT_SYMBOL(rtc_lock);
28 
29 /*
30  * In order to set the CMOS clock precisely, mach_set_cmos_time has to be
31  * called 500 ms after the second nowtime has started, because when
32  * nowtime is written into the registers of the CMOS clock, it will
33  * jump to the next second precisely 500 ms later. Check the Motorola
34  * MC146818A or Dallas DS12887 data sheet for details.
35  */
mach_set_cmos_time(const struct timespec64 * now)36 int mach_set_cmos_time(const struct timespec64 *now)
37 {
38 	unsigned long long nowtime = now->tv_sec;
39 	struct rtc_time tm;
40 	int retval = 0;
41 
42 	rtc_time64_to_tm(nowtime, &tm);
43 	if (!rtc_valid_tm(&tm)) {
44 		retval = mc146818_set_time(&tm);
45 		if (retval)
46 			printk(KERN_ERR "%s: RTC write failed with error %d\n",
47 			       __func__, retval);
48 	} else {
49 		printk(KERN_ERR
50 		       "%s: Invalid RTC value: write of %llx to RTC failed\n",
51 			__func__, nowtime);
52 		retval = -EINVAL;
53 	}
54 	return retval;
55 }
56 
mach_get_cmos_time(struct timespec64 * now)57 void mach_get_cmos_time(struct timespec64 *now)
58 {
59 	struct rtc_time tm;
60 
61 	/*
62 	 * If pm_trace abused the RTC as storage, set the timespec to 0,
63 	 * which tells the caller that this RTC value is unusable.
64 	 */
65 	if (!pm_trace_rtc_valid()) {
66 		now->tv_sec = now->tv_nsec = 0;
67 		return;
68 	}
69 
70 	if (mc146818_get_time(&tm, 1000)) {
71 		pr_err("Unable to read current time from RTC\n");
72 		now->tv_sec = now->tv_nsec = 0;
73 		return;
74 	}
75 
76 	now->tv_sec = rtc_tm_to_time64(&tm);
77 	now->tv_nsec = 0;
78 }
79 
80 /* Routines for accessing the CMOS RAM/RTC. */
rtc_cmos_read(unsigned char addr)81 unsigned char rtc_cmos_read(unsigned char addr)
82 {
83 	unsigned char val;
84 
85 	lock_cmos_prefix(addr);
86 	outb(addr, RTC_PORT(0));
87 	val = inb(RTC_PORT(1));
88 	lock_cmos_suffix(addr);
89 
90 	return val;
91 }
92 EXPORT_SYMBOL(rtc_cmos_read);
93 
rtc_cmos_write(unsigned char val,unsigned char addr)94 void rtc_cmos_write(unsigned char val, unsigned char addr)
95 {
96 	lock_cmos_prefix(addr);
97 	outb(addr, RTC_PORT(0));
98 	outb(val, RTC_PORT(1));
99 	lock_cmos_suffix(addr);
100 }
101 EXPORT_SYMBOL(rtc_cmos_write);
102 
update_persistent_clock64(struct timespec64 now)103 int update_persistent_clock64(struct timespec64 now)
104 {
105 	return x86_platform.set_wallclock(&now);
106 }
107 
108 /* not static: needed by APM */
read_persistent_clock64(struct timespec64 * ts)109 void read_persistent_clock64(struct timespec64 *ts)
110 {
111 	x86_platform.get_wallclock(ts);
112 }
113 
114 
115 static struct resource rtc_resources[] = {
116 	[0] = {
117 		.start	= RTC_PORT(0),
118 		.end	= RTC_PORT(1),
119 		.flags	= IORESOURCE_IO,
120 	},
121 	[1] = {
122 		.start	= RTC_IRQ,
123 		.end	= RTC_IRQ,
124 		.flags	= IORESOURCE_IRQ,
125 	}
126 };
127 
128 static struct platform_device rtc_device = {
129 	.name		= "rtc_cmos",
130 	.id		= -1,
131 	.resource	= rtc_resources,
132 	.num_resources	= ARRAY_SIZE(rtc_resources),
133 };
134 
add_rtc_cmos(void)135 static __init int add_rtc_cmos(void)
136 {
137 #ifdef CONFIG_PNP
138 	static const char * const ids[] __initconst =
139 	    { "PNP0b00", "PNP0b01", "PNP0b02", };
140 	struct pnp_dev *dev;
141 	int i;
142 
143 	pnp_for_each_dev(dev) {
144 		for (i = 0; i < ARRAY_SIZE(ids); i++) {
145 			if (compare_pnp_id(dev->id, ids[i]) != 0)
146 				return 0;
147 		}
148 	}
149 #endif
150 	if (!x86_platform.legacy.rtc)
151 		return -ENODEV;
152 
153 	platform_device_register(&rtc_device);
154 	dev_info(&rtc_device.dev,
155 		 "registered platform RTC device (no PNP device found)\n");
156 
157 	return 0;
158 }
159 device_initcall(add_rtc_cmos);
160