arch/x86/kernel/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/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  */
  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
  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. */
  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
  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
 103 int update_persistent_clock64(struct timespec64 now)
 104 {
 105         return x86_platform.set_wallclock(&now);
 106 }
 107
 108 /* not static: needed by APM */
 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
 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);