109 lines
2.1 KiB
C
109 lines
2.1 KiB
C
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#include <stdio.h>
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#include <time.h>
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#include <sys/times.h>
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#include <sys/types.h>
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#include <minix/u64.h>
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#include <minix/config.h>
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#include <minix/const.h>
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#include <minix/minlib.h>
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#include "sysutil.h"
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#ifndef CONFIG_MAX_CPUS
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#define CONFIG_MAX_CPUS 1
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#endif
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#define MICROHZ 1000000 /* number of micros per second */
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#define MICROSPERTICK(h) (MICROHZ/(h)) /* number of micros per HZ tick */
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#define CALIBRATE \
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if(!calibrated) { \
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int r; \
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if((r=tsc_calibrate()) != OK) \
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panic("calibrate failed: %d", r); \
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}
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static u32_t calib_mhz, Hz = 0;
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static int calibrated = 0;
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int
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tsc_calibrate(void)
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{
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struct cpu_info cpu_info[CONFIG_MAX_CPUS];
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/* Get HZ. */
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Hz = sys_hz();
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/* Obtain CPU frequency from kernel */
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if (sys_getcpuinfo(&cpu_info)) {
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printf("tsc_calibrate: cannot get cpu info\n");
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return -1;
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}
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/* For now, use the frequency of the first CPU; everything here will
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* break down in case we get scheduled on multiple CPUs with different
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* frequencies regardless
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*/
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calib_mhz = cpu_info[0].freq;
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calibrated = 1;
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return OK;
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}
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int
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micro_delay(u32_t micros)
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{
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u64_t now, end;
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/* Start of delay. */
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read_tsc_64(&now);
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CALIBRATE;
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/* We have to know when to end the delay. */
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end = add64(now, mul64u(micros, calib_mhz));
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/* If we have to wait for at least one HZ tick, use the regular
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* tickdelay first. Round downwards on purpose, so the average
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* half-tick we wait short (depending on where in the current tick
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* we call tickdelay). We can correct for both overhead of tickdelay
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* itself and the short wait in the busywait later.
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*/
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if(micros >= MICROSPERTICK(Hz))
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tickdelay(micros*Hz/MICROHZ);
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/* Wait (the rest) of the delay time using busywait. */
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while(cmp64(now, end) < 0)
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read_tsc_64(&now);
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return OK;
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}
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u32_t tsc_64_to_micros(u64_t tsc)
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{
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u64_t tmp;
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CALIBRATE;
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tmp = div64u64(tsc, calib_mhz);
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if (ex64hi(tmp)) {
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printf("tsc_64_to_micros: more than 2^32ms\n");
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return ~0UL;
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} else {
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return ex64lo(tmp);
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}
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}
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u32_t tsc_to_micros(u32_t low, u32_t high)
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{
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return tsc_64_to_micros(make64(low, high));
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}
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u32_t tsc_get_khz(void)
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{
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CALIBRATE;
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return calib_mhz * 1000;
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}
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