src/arch/i386/drivers/timer_rtdsc.c

   1
   2 #include <gpxe/init.h>
   3 #include <gpxe/timer.h>
   4 #include <stdio.h>
   5 #include <bits/cpu.h>
   6 #include <bits/timer2.h>
   7 #include <io.h>
   8
   9
  10 #define rdtsc(low,high) \
  11      __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
  12
  13 #define rdtscll(val) \
  14      __asm__ __volatile__ ("rdtsc" : "=A" (val))
  15
  16 static unsigned long long calibrate_tsc(void)
  17 {
  18         uint32_t startlow, starthigh;
  19         uint32_t endlow, endhigh;
  20
  21         rdtsc(startlow,starthigh);
  22         i386_timer2_udelay(USECS_IN_MSEC/2);
  23         rdtsc(endlow,endhigh);
  24
  25         /* 64-bit subtract - gcc just messes up with long longs */
  26         /* XXX ORLY? Check it. */
  27         __asm__("subl %2,%0\n\t"
  28                 "sbbl %3,%1"
  29                 :"=a" (endlow), "=d" (endhigh)
  30                 :"g" (startlow), "g" (starthigh),
  31                 "0" (endlow), "1" (endhigh));
  32
  33         /* Error: ECPUTOOFAST */
  34         if (endhigh)
  35                 goto bad_ctc;
  36
  37         endlow *= MSECS_IN_SEC*2;
  38         return endlow;
  39
  40         /*
  41          * The CTC wasn't reliable: we got a hit on the very first read,
  42          * or the CPU was so fast/slow that the quotient wouldn't fit in
  43          * 32 bits..
  44          */
  45 bad_ctc:
  46         return 0;
  47 }
  48 static uint32_t clocks_per_second = 0;
  49
  50 static tick_t rtdsc_currticks(void)
  51 {
  52         uint32_t clocks_high, clocks_low;
  53         uint32_t currticks;
  54
  55         /* Read the Time Stamp Counter */
  56         rdtsc(clocks_low, clocks_high);
  57
  58         /* currticks = clocks / clocks_per_tick; */
  59         __asm__("divl %1"
  60                 :"=a" (currticks)
  61                 :"r" (clocks_per_second/USECS_IN_SEC), "0" (clocks_low), "d" (clocks_high));
  62
  63         return currticks;
  64 }
  65
  66 static int rtdsc_ts_init(void)
  67 {
  68
  69         struct cpuinfo_x86 cpu_info;
  70
  71         get_cpuinfo(&cpu_info);
  72         if (cpu_info.features & X86_FEATURE_TSC) {
  73                 clocks_per_second = calibrate_tsc();
  74                 if (clocks_per_second) {
  75                         DBG("RTDSC Ticksource installed. CPU running at %ld Mhz\n",
  76                                 clocks_per_second/(1000*1000));
  77                         return 0;
  78                 }
  79         }
  80
  81         printf("RTDSC timer not available on this machine.\n");
  82         return 1;
  83 }
  84
  85 struct timer rtdsc_ts __timer (01) = {
  86         .init = rtdsc_ts_init,
  87         .udelay = generic_currticks_udelay,
  88         .currticks = rtdsc_currticks,
  89 };
  90