x86timer.cpp

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/** @file: x86timer.c  API for x86 time funcs.
 * thanks to Ben Penaflor 

First run

. ./setup.clocks2 3 0 64 2
init_clocks_mbcb

    telnet 192.5.166.179
    /tmp/trigger_toggler

******************************************************************************
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "x86timer.h"

static unsigned int CPU_CLOCK_SPEED = -1;

#define rdtscll(val) \
     __asm__ __volatile__ ("rdtsc" : "=A" (val))


unsigned long long get_cpu_ticks(void)
{
        unsigned long long ticks;
        
        rdtscll(ticks);
        return ticks;
}
unsigned long long get_cpu_usecs(void)
{
        unsigned long long ticks;
        
        rdtscll(ticks);
        return ticks/CPU_CLOCK_SPEED;
}


/*
******************************************************************************
SUBROUTINE: get_cpu_clock_speed
******************************************************************************
*/

unsigned int get_cpu_clock_speed(void)
{
        char line[256];
        FILE *inputfile;
        float fspeed = 0;
        unsigned int speed;

        if(CPU_CLOCK_SPEED == -1)
        {
                speed = 0;
                /*
                  Get the cpu speed.
                  Open the file.
                */
                inputfile = fopen("/proc/cpuinfo", "r");
                if(inputfile != NULL)
                {
                        /*
                          Read the data from the file.
                        */
                        while(fgets(line, 256, inputfile) != NULL)
                        {
                                if(strstr(line,"cycle frequency [Hz]") != NULL)
                                {
                                        fspeed = (float)atoi(strchr(line,':')+1)/1000000.0;
                                        break;
                                }
                                if(strstr(line,"cpu MHz") != NULL)
                                {
                                        fspeed = (float)atoi(strchr(line,':')+1);
                                        break;
                                }
                        }
                        fclose(inputfile);
                        speed = (int)(fspeed);
                }
                else
                        fprintf(stderr,"Cannot get cpu speed from /proc/cpuinfo\n");

                fprintf(stderr,"speed=%d ticks per microsecond\n", speed);
                CPU_CLOCK_SPEED=speed;
        }

        return(CPU_CLOCK_SPEED);
}



/*
******************************************************************************
SUBROUTINE: cpu_delay_awhile

Delay the specified number of input microseconds.

{// for testing, this delays for 10 seconds
int ii;
printf("delaying\n");
for(ii=0;ii<1000*10;ii++)
    cpu_delay_awhile(1000);
printf("done\n");
}
******************************************************************************
*/


static unsigned long
_get_elapsed_microseconds(int reset, unsigned long long* start)
{
        unsigned long long now;

        if(reset==1){
                *start = get_cpu_usecs();
                return 0;
        }
        now = get_cpu_usecs();

        if (now >= *start){
                return now - *start;
        }else{
                *start = 0;
                return 0xffffffffffffffffULL - *start + now;
                /**    0x1234567890abcdefULL */
        }
}


unsigned long
get_elapsed_microseconds(int reset)
{
        static unsigned long long start;

        return _get_elapsed_microseconds(reset, &start);
}


void cpu_delay_awhile(unsigned int delay_microseconds)
{
        unsigned long long _start;
        unsigned long start = _get_elapsed_microseconds(1, &_start);
        unsigned long now;

        do {
                now = _get_elapsed_microseconds(0, &_start);
        } while( now < start + delay_microseconds);
}