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Linux/arch/x86/kernel/rtc.c

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  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/acpi.h>
  8 #include <linux/bcd.h>
  9 #include <linux/export.h>
 10 #include <linux/pnp.h>
 11 #include <linux/of.h>
 12 
 13 #include <asm/vsyscall.h>
 14 #include <asm/x86_init.h>
 15 #include <asm/time.h>
 16 #include <asm/intel-mid.h>
 17 #include <asm/setup.h>
 18 
 19 #ifdef CONFIG_X86_32
 20 /*
 21  * This is a special lock that is owned by the CPU and holds the index
 22  * register we are working with.  It is required for NMI access to the
 23  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
 24  */
 25 volatile unsigned long cmos_lock;
 26 EXPORT_SYMBOL(cmos_lock);
 27 #endif /* CONFIG_X86_32 */
 28 
 29 /* For two digit years assume time is always after that */
 30 #define CMOS_YEARS_OFFS 2000
 31 
 32 DEFINE_SPINLOCK(rtc_lock);
 33 EXPORT_SYMBOL(rtc_lock);
 34 
 35 /*
 36  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
 37  * called 500 ms after the second nowtime has started, because when
 38  * nowtime is written into the registers of the CMOS clock, it will
 39  * jump to the next second precisely 500 ms later. Check the Motorola
 40  * MC146818A or Dallas DS12887 data sheet for details.
 41  */
 42 int mach_set_rtc_mmss(const struct timespec64 *now)
 43 {
 44         unsigned long long nowtime = now->tv_sec;
 45         struct rtc_time tm;
 46         int retval = 0;
 47 
 48         rtc_time64_to_tm(nowtime, &tm);
 49         if (!rtc_valid_tm(&tm)) {
 50                 retval = mc146818_set_time(&tm);
 51                 if (retval)
 52                         printk(KERN_ERR "%s: RTC write failed with error %d\n",
 53                                __func__, retval);
 54         } else {
 55                 printk(KERN_ERR
 56                        "%s: Invalid RTC value: write of %llx to RTC failed\n",
 57                         __func__, nowtime);
 58                 retval = -EINVAL;
 59         }
 60         return retval;
 61 }
 62 
 63 void mach_get_cmos_time(struct timespec64 *now)
 64 {
 65         unsigned int status, year, mon, day, hour, min, sec, century = 0;
 66         unsigned long flags;
 67 
 68         /*
 69          * If pm_trace abused the RTC as storage, set the timespec to 0,
 70          * which tells the caller that this RTC value is unusable.
 71          */
 72         if (!pm_trace_rtc_valid()) {
 73                 now->tv_sec = now->tv_nsec = 0;
 74                 return;
 75         }
 76 
 77         spin_lock_irqsave(&rtc_lock, flags);
 78 
 79         /*
 80          * If UIP is clear, then we have >= 244 microseconds before
 81          * RTC registers will be updated.  Spec sheet says that this
 82          * is the reliable way to read RTC - registers. If UIP is set
 83          * then the register access might be invalid.
 84          */
 85         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 86                 cpu_relax();
 87 
 88         sec = CMOS_READ(RTC_SECONDS);
 89         min = CMOS_READ(RTC_MINUTES);
 90         hour = CMOS_READ(RTC_HOURS);
 91         day = CMOS_READ(RTC_DAY_OF_MONTH);
 92         mon = CMOS_READ(RTC_MONTH);
 93         year = CMOS_READ(RTC_YEAR);
 94 
 95 #ifdef CONFIG_ACPI
 96         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 97             acpi_gbl_FADT.century)
 98                 century = CMOS_READ(acpi_gbl_FADT.century);
 99 #endif
100 
101         status = CMOS_READ(RTC_CONTROL);
102         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
103 
104         spin_unlock_irqrestore(&rtc_lock, flags);
105 
106         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
107                 sec = bcd2bin(sec);
108                 min = bcd2bin(min);
109                 hour = bcd2bin(hour);
110                 day = bcd2bin(day);
111                 mon = bcd2bin(mon);
112                 year = bcd2bin(year);
113         }
114 
115         if (century) {
116                 century = bcd2bin(century);
117                 year += century * 100;
118         } else
119                 year += CMOS_YEARS_OFFS;
120 
121         now->tv_sec = mktime64(year, mon, day, hour, min, sec);
122         now->tv_nsec = 0;
123 }
124 
125 /* Routines for accessing the CMOS RAM/RTC. */
126 unsigned char rtc_cmos_read(unsigned char addr)
127 {
128         unsigned char val;
129 
130         lock_cmos_prefix(addr);
131         outb(addr, RTC_PORT(0));
132         val = inb(RTC_PORT(1));
133         lock_cmos_suffix(addr);
134 
135         return val;
136 }
137 EXPORT_SYMBOL(rtc_cmos_read);
138 
139 void rtc_cmos_write(unsigned char val, unsigned char addr)
140 {
141         lock_cmos_prefix(addr);
142         outb(addr, RTC_PORT(0));
143         outb(val, RTC_PORT(1));
144         lock_cmos_suffix(addr);
145 }
146 EXPORT_SYMBOL(rtc_cmos_write);
147 
148 int update_persistent_clock64(struct timespec64 now)
149 {
150         return x86_platform.set_wallclock(&now);
151 }
152 
153 /* not static: needed by APM */
154 void read_persistent_clock64(struct timespec64 *ts)
155 {
156         x86_platform.get_wallclock(ts);
157 }
158 
159 
160 static struct resource rtc_resources[] = {
161         [0] = {
162                 .start  = RTC_PORT(0),
163                 .end    = RTC_PORT(1),
164                 .flags  = IORESOURCE_IO,
165         },
166         [1] = {
167                 .start  = RTC_IRQ,
168                 .end    = RTC_IRQ,
169                 .flags  = IORESOURCE_IRQ,
170         }
171 };
172 
173 static struct platform_device rtc_device = {
174         .name           = "rtc_cmos",
175         .id             = -1,
176         .resource       = rtc_resources,
177         .num_resources  = ARRAY_SIZE(rtc_resources),
178 };
179 
180 static __init int add_rtc_cmos(void)
181 {
182 #ifdef CONFIG_PNP
183         static const char * const ids[] __initconst =
184             { "PNP0b00", "PNP0b01", "PNP0b02", };
185         struct pnp_dev *dev;
186         struct pnp_id *id;
187         int i;
188 
189         pnp_for_each_dev(dev) {
190                 for (id = dev->id; id; id = id->next) {
191                         for (i = 0; i < ARRAY_SIZE(ids); i++) {
192                                 if (compare_pnp_id(id, ids[i]) != 0)
193                                         return 0;
194                         }
195                 }
196         }
197 #endif
198         if (!x86_platform.legacy.rtc)
199                 return -ENODEV;
200 
201         platform_device_register(&rtc_device);
202         dev_info(&rtc_device.dev,
203                  "registered platform RTC device (no PNP device found)\n");
204 
205         return 0;
206 }
207 device_initcall(add_rtc_cmos);
208 

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