grub-core/kern/i386/tsc.c

   1 /* kern/i386/tsc.c - x86 TSC time source implementation
   2  * Requires Pentium or better x86 CPU that supports the RDTSC instruction.
   3  * This module uses the RTC (via grub_get_rtc()) to calibrate the TSC to
   4  * real time.
   5  *
   6  *  GRUB  --  GRand Unified Bootloader
   7  *  Copyright (C) 2008  Free Software Foundation, Inc.
   8  *
   9  *  GRUB is free software: you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation, either version 3 of the License, or
  12  *  (at your option) any later version.
  13  *
  14  *  GRUB is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23 #include <grub/types.h>
  24 #include <grub/time.h>
  25 #include <grub/misc.h>
  26 #include <grub/i386/tsc.h>
  27 #include <grub/i386/cpuid.h>
  28 #include <grub/i386/pit.h>
  29 #include <grub/cpu/io.h>
  30
  31 /* This defines the value TSC had at the epoch (that is, when we calibrated it). */
  32 static grub_uint64_t tsc_boot_time;
  33
  34 /* Calibrated TSC rate.  (In ms per 2^32 ticks) */
  35 /* We assume that the tick is less than 1 ms and hence this value fits
  36    in 32-bit.  */
  37 grub_uint32_t grub_tsc_rate;
  38
  39 /* Read the TSC value, which increments with each CPU clock cycle. */
  40 static __inline grub_uint64_t
  41 grub_get_tsc (void)
  42 {
  43   grub_uint32_t lo, hi;
  44
  45   /* The CPUID instruction is a 'serializing' instruction, and
  46      avoids out-of-order execution of the RDTSC instruction. */
  47 #ifdef __APPLE__
  48   __asm__ __volatile__ ("xorl %%eax, %%eax\n\t"
  49 #ifdef __x86_64__
  50                         "push %%rbx\n"
  51 #else
  52                         "push %%ebx\n"
  53 #endif
  54                         "cpuid\n"
  55 #ifdef __x86_64__
  56                         "pop %%rbx\n"
  57 #else
  58                         "pop %%ebx\n"
  59 #endif
  60                         :::"%rax", "%rcx", "%rdx");
  61 #else
  62   __asm__ __volatile__ ("xorl %%eax, %%eax\n\t"
  63                         "cpuid":::"%rax", "%rbx", "%rcx", "%rdx");
  64 #endif
  65   /* Read TSC value.  We cannot use "=A", since this would use
  66      %rax on x86_64. */
  67   __asm__ __volatile__ ("rdtsc":"=a" (lo), "=d" (hi));
  68
  69   return (((grub_uint64_t) hi) << 32) | lo;
  70 }
  71
  72 static __inline int
  73 grub_cpu_is_tsc_supported (void)
  74 {
  75   if (! grub_cpu_is_cpuid_supported ())
  76     return 0;
  77
  78   grub_uint32_t features;
  79 #ifdef __APPLE__
  80   __asm__ ("movl $1, %%eax\n\t"
  81 #ifdef __x86_64__
  82            "push %%rbx\n"
  83 #else
  84            "push %%ebx\n"
  85 #endif
  86            "cpuid\n"
  87 #ifdef __x86_64__
  88            "pop %%rbx\n"
  89 #else
  90            "pop %%ebx\n"
  91 #endif
  92            : "=d" (features)
  93            : /* No inputs.  */
  94            : /* Clobbered:  */ "%rax", "%rcx");
  95 #else
  96   __asm__ ("movl $1, %%eax\n\t"
  97            "cpuid\n"
  98            : "=d" (features)
  99            : /* No inputs.  */
 100            : /* Clobbered:  */ "%rax", "%rbx", "%rcx");
 101 #endif
 102   return (features & (1 << 4)) != 0;
 103 }
 104
 105 static void
 106 grub_pit_wait (grub_uint16_t tics)
 107 {
 108   /* Disable timer2 gate and speaker.  */
 109   grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
 110              & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
 111              GRUB_PIT_SPEAKER_PORT);
 112
 113   /* Set tics.  */
 114   grub_outb (GRUB_PIT_CTRL_SELECT_2 | GRUB_PIT_CTRL_READLOAD_WORD,
 115              GRUB_PIT_CTRL);
 116   grub_outb (tics & 0xff, GRUB_PIT_COUNTER_2);
 117   grub_outb (tics >> 8, GRUB_PIT_COUNTER_2);
 118
 119   /* Enable timer2 gate, keep speaker disabled.  */
 120   grub_outb ((grub_inb (GRUB_PIT_SPEAKER_PORT) & ~ GRUB_PIT_SPK_DATA)
 121              | GRUB_PIT_SPK_TMR2,
 122              GRUB_PIT_SPEAKER_PORT);
 123
 124   /* Wait.  */
 125   while ((grub_inb (GRUB_PIT_SPEAKER_PORT) & GRUB_PIT_SPK_TMR2_LATCH) == 0x00);
 126
 127   /* Disable timer2 gate and speaker.  */
 128   grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
 129              & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
 130              GRUB_PIT_SPEAKER_PORT);
 131 }
 132
 133 static grub_uint64_t
 134 grub_tsc_get_time_ms (void)
 135 {
 136   grub_uint64_t a = grub_get_tsc () - tsc_boot_time;
 137   grub_uint64_t ah = a >> 32;
 138   grub_uint64_t al = a & 0xffffffff;
 139
 140   return ((al * grub_tsc_rate) >> 32) + ah * grub_tsc_rate;
 141 }
 142
 143 /* Calibrate the TSC based on the RTC.  */
 144 static void
 145 calibrate_tsc (void)
 146 {
 147   /* First calibrate the TSC rate (relative, not absolute time). */
 148   grub_uint64_t end_tsc;
 149
 150   tsc_boot_time = grub_get_tsc ();
 151   grub_pit_wait (0xffff);
 152   end_tsc = grub_get_tsc ();
 153
 154   grub_tsc_rate = grub_divmod64 ((55ULL << 32), end_tsc - tsc_boot_time, 0);
 155 }
 156
 157 void
 158 grub_tsc_init (void)
 159 {
 160   if (grub_cpu_is_tsc_supported ())
 161     {
 162       calibrate_tsc ();
 163       grub_install_get_time_ms (grub_tsc_get_time_ms);
 164     }
 165   else
 166     {
 167 #if defined (GRUB_MACHINE_PCBIOS) || defined (GRUB_MACHINE_IEEE1275)
 168       grub_install_get_time_ms (grub_rtc_get_time_ms);
 169 #else
 170       grub_fatal ("no TSC found");
 171 #endif
 172     }
 173 }