rtc.c

  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/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#ifdef CONFIG_PNP
137	static const char * const ids[] __initconst =
138	    { "PNP0b00", "PNP0b01", "PNP0b02", };
139	struct pnp_dev *dev;
140	int i;
141
142	pnp_for_each_dev(dev) {
143		for (i = 0; i < ARRAY_SIZE(ids); i++) {
144			if (compare_pnp_id(dev->id, ids[i]) != 0)
145				return 0;
146		}
147	}
148#endif
149	if (!x86_platform.legacy.rtc)
150		return -ENODEV;
151
152	platform_device_register(&rtc_device);
153	dev_info(&rtc_device.dev,
154		 "registered platform RTC device (no PNP device found)\n");
155
156	return 0;
157}
158device_initcall(add_rtc_cmos);