src/arch/i386/drivers/timer_rtdsc.c

   1
   2 #include <gpxe/init.h>
   3 #include <gpxe/timer.h>
   4 #include <errno.h>
   5 #include <stdio.h>
   6 #include <bits/cpu.h>
   7 #include <bits/timer2.h>
   8 #include <io.h>
   9
  10
  11 #define rdtsc(low,high) \
  12      __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
  13
  14 #define rdtscll(val) \
  15      __asm__ __volatile__ ("rdtsc" : "=A" (val))
  16
  17 static unsigned long long calibrate_tsc(void)
  18 {
  19         uint32_t startlow, starthigh;
  20         uint32_t endlow, endhigh;
  21
  22         rdtsc(startlow,starthigh);
  23         i386_timer2_udelay(USECS_IN_MSEC/2);
  24         rdtsc(endlow,endhigh);
  25
  26         /* 64-bit subtract - gcc just messes up with long longs */
  27         /* XXX ORLY? Check it. */
  28         __asm__("subl %2,%0\n\t"
  29                 "sbbl %3,%1"
  30                 :"=a" (endlow), "=d" (endhigh)
  31                 :"g" (startlow), "g" (starthigh),
  32                 "0" (endlow), "1" (endhigh));
  33
  34         /* Error: ECPUTOOFAST */
  35         if (endhigh)
  36                 goto bad_ctc;
  37
  38         endlow *= MSECS_IN_SEC*2;
  39         return endlow;
  40
  41         /*
  42          * The CTC wasn't reliable: we got a hit on the very first read,
  43          * or the CPU was so fast/slow that the quotient wouldn't fit in
  44          * 32 bits..
  45          */
  46 bad_ctc:
  47         return 0;
  48 }
  49 static uint32_t clocks_per_second = 0;
  50
  51 static tick_t rtdsc_currticks(void)
  52 {
  53         uint32_t clocks_high, clocks_low;
  54         uint32_t currticks;
  55
  56         /* Read the Time Stamp Counter */
  57         rdtsc(clocks_low, clocks_high);
  58
  59         /* currticks = clocks / clocks_per_tick; */
  60         __asm__("divl %1"
  61                 :"=a" (currticks)
  62                 :"r" (clocks_per_second/USECS_IN_SEC), "0" (clocks_low), "d" (clocks_high));
  63
  64         return currticks;
  65 }
  66
  67 static int rtdsc_ts_init(void)
  68 {
  69
  70         struct cpuinfo_x86 cpu_info;
  71
  72         get_cpuinfo(&cpu_info);
  73         if (cpu_info.features & X86_FEATURE_TSC) {
  74                 clocks_per_second = calibrate_tsc();
  75                 if (clocks_per_second) {
  76                         DBG("RTDSC Ticksource installed. CPU running at %ld Mhz\n",
  77                                 clocks_per_second/(1000*1000));
  78                         return 0;
  79                 }
  80         }
  81
  82         DBG("RTDSC timer not available on this machine.\n");
  83         return -ENODEV;
  84 }
  85
  86 struct timer rtdsc_ts __timer (01) = {
  87         .init = rtdsc_ts_init,
  88         .udelay = generic_currticks_udelay,
  89         .currticks = rtdsc_currticks,
  90 };
  91