osfmk/i386/rtclock.h

   1 /*
   2  * Copyright (c) 2004-2007 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29  * @OSF_COPYRIGHT@
  30  */
  31 /*
  32  * @APPLE_FREE_COPYRIGHT@
  33  */
  34 /*
  35  *      File:           rtclock.h
  36  *      Purpose:        Routines for handling the machine dependent
  37  *                              real-time clock.
  38  */
  39
  40 #ifndef _I386_RTCLOCK_H_
  41 #define _I386_RTCLOCK_H_
  42
  43 #ifndef ASSEMBLER
  44 typedef struct rtc_nanotime {
  45         uint64_t        tsc_base;               /* timestamp */
  46         uint64_t        ns_base;                /* nanoseconds */
  47         uint32_t        scale;                  /* tsc -> nanosec multiplier */
  48         uint32_t        shift;                  /* tsc -> nanosec shift/div */
  49                                                 /* shift is overloaded with
  50                                                  * lower 32bits of tsc_freq
  51                                                  * on slower machines (SLOW_TSC_THRESHOLD) */
  52         uint32_t        generation;             /* 0 == being updated */
  53         uint32_t        spare1;
  54 } rtc_nanotime_t;
  55
  56 #include <kern/etimer.h>
  57
  58 struct cpu_data;
  59
  60 extern uint64_t tsc_rebase_abs_time;
  61
  62 extern void     _rtc_nanotime_store(
  63                         uint64_t        tsc,
  64                         uint64_t        nsec,
  65                         uint32_t        scale,
  66                         uint32_t        shift,
  67                         rtc_nanotime_t  *dst);
  68
  69 extern uint64_t _rtc_nanotime_read(
  70                         rtc_nanotime_t  *rntp,
  71                         int             slow);
  72
  73 extern rtc_nanotime_t rtc_nanotime_info;
  74 #endif
  75
  76 #define SLOW_TSC_THRESHOLD      1000067800      /* TSC is too slow for regular nanotime() algorithm */
  77
  78 #if defined(__i386__)
  79 /*
  80  * Assembly snippet included in exception handlers and rtc_nanotime_read()
  81  * %edi points to nanotime info struct
  82  * %edx:%eax returns nanotime
  83  */
  84 #define RTC_NANOTIME_READ_FAST()                                          \
  85 0:      movl    RNT_GENERATION(%edi),%esi       /* being updated? */    ; \
  86         testl   %esi,%esi                                               ; \
  87         jz      0b                              /* wait until done */   ; \
  88         lfence                                                          ; \
  89         rdtsc                                                           ; \
  90         lfence                                                          ; \
  91         subl    RNT_TSC_BASE(%edi),%eax                                 ; \
  92         sbbl    RNT_TSC_BASE+4(%edi),%edx       /* tsc - tsc_base */    ; \
  93         movl    RNT_SCALE(%edi),%ecx            /* * scale factor */    ; \
  94         movl    %edx,%ebx                                               ; \
  95         mull    %ecx                                                    ; \
  96         movl    %ebx,%eax                                               ; \
  97         movl    %edx,%ebx                                               ; \
  98         mull    %ecx                                                    ; \
  99         addl    %ebx,%eax                                               ; \
 100         adcl    $0,%edx                                                 ; \
 101         addl    RNT_NS_BASE(%edi),%eax          /* + ns_base */         ; \
 102         adcl    RNT_NS_BASE+4(%edi),%edx                                ; \
 103         cmpl    RNT_GENERATION(%edi),%esi       /* check for update */  ; \
 104         jne     0b                              /* do it all again */
 105
 106 #elif defined(__x86_64__)
 107
 108 /*
 109  * Assembly snippet included in exception handlers and rtc_nanotime_read()
 110  * %rdi points to nanotime info struct.
 111  * %rax returns nanotime
 112  */
 113 #define RTC_NANOTIME_READ_FAST()                                          \
 114 0:      movl    RNT_GENERATION(%rdi),%esi                               ; \
 115         test    %esi,%esi                       /* info updating? */    ; \
 116         jz      0b                              /* - wait if so */      ; \
 117         lfence                                                          ; \
 118         rdtsc                                                           ; \
 119         lfence                                                          ; \
 120         shlq    $32,%rdx                                                ; \
 121         orq     %rdx,%rax                       /* %rax := tsc */       ; \
 122         subq    RNT_TSC_BASE(%rdi),%rax         /* tsc - tsc_base */    ; \
 123         xorq    %rcx,%rcx                                               ; \
 124         movl    RNT_SCALE(%rdi),%ecx                                    ; \
 125         mulq    %rcx                            /* delta * scale */     ; \
 126         shrdq   $32,%rdx,%rax                   /* %rdx:%rax >>= 32 */  ; \
 127         addq    RNT_NS_BASE(%rdi),%rax          /* add ns_base */       ; \
 128         cmpl    RNT_GENERATION(%rdi),%esi       /* repeat if changed */ ; \
 129         jne     0b
 130
 131 #endif
 132
 133 #endif /* _I386_RTCLOCK_H_ */