mirror of
https://github.com/servalproject/serval-dna.git
synced 2024-12-26 00:01:12 +00:00
74 lines
2.0 KiB
C
74 lines
2.0 KiB
C
|
/*
|
||
|
|
cpucycles/cortex.c version 20101203
|
||
|
|
D. J. Bernstein
|
||
|
|
Public domain.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#define SCALE 1
|
||
|
|
#include <time.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <sys/time.h>
|
||
|
|
|
||
|
|
static int enabled = 0;
|
||
|
|
|
||
|
|
static int prev[3];
|
||
|
|
static unsigned long long prevcycles = 0;
|
||
|
|
static int now[3];
|
||
|
|
static long long cyclespersec = 0;
|
||
|
|
|
||
|
|
static void readticks(unsigned int *result)
|
||
|
|
{
|
||
|
|
struct timeval t;
|
||
|
|
unsigned int cc;
|
||
|
|
if (!enabled) {
|
||
|
|
asm volatile("mcr p15, 0, %0, c9, c12, 0" :: "r"(17));
|
||
|
|
asm volatile("mcr p15, 0, %0, c9, c12, 1" :: "r"(0x8000000f));
|
||
|
|
asm volatile("mcr p15, 0, %0, c9, c12, 3" :: "r"(0x8000000f));
|
||
|
|
enabled = 1;
|
||
|
|
}
|
||
|
|
asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r"(cc));
|
||
|
|
gettimeofday(&t,(struct timezone *) 0);
|
||
|
|
result[0] = cc;
|
||
|
|
result[1] = t.tv_usec;
|
||
|
|
result[2] = t.tv_sec;
|
||
|
|
}
|
||
|
|
|
||
|
|
long long cpucycles_cortex(void)
|
||
|
|
{
|
||
|
|
unsigned long long delta4;
|
||
|
|
int deltan;
|
||
|
|
int deltas;
|
||
|
|
unsigned long long guesscycles;
|
||
|
|
|
||
|
|
readticks(now);
|
||
|
|
delta4 = (unsigned int) (now[0] - prev[0]); /* unsigned change in number of cycles mod 2^32 */
|
||
|
|
deltan = now[1] - prev[1]; /* signed change in number of nanoseconds mod 10^9 */
|
||
|
|
deltas = now[2] - prev[2]; /* signed change in number of seconds */
|
||
|
|
if ((deltas == 0 && deltan < 200000) || (deltas == 1 && deltan < -800000))
|
||
|
|
return (prevcycles + delta4) * SCALE;
|
||
|
|
|
||
|
|
prev[0] = now[0];
|
||
|
|
prev[1] = now[1];
|
||
|
|
prev[2] = now[2];
|
||
|
|
|
||
|
|
if ((deltas == 0 && deltan < 300000) || (deltas == 1 && deltan < -700000)) {
|
||
|
|
// actual number of cycles cannot have increased by 2^32 in <0.3ms
|
||
|
|
cyclespersec = 1000000 * (unsigned long long) delta4;
|
||
|
|
cyclespersec /= deltan + 1000000 * (long long) deltas;
|
||
|
|
} else {
|
||
|
|
guesscycles = deltas * cyclespersec;
|
||
|
|
guesscycles += (deltan * cyclespersec) / 1000000;
|
||
|
|
while (delta4 + 2147483648ULL < guesscycles) delta4 += 4294967296ULL;
|
||
|
|
/* XXX: could do longer-term extrapolation here */
|
||
|
|
}
|
||
|
|
|
||
|
|
prevcycles += delta4;
|
||
|
|
return prevcycles * SCALE;
|
||
|
|
}
|
||
|
|
|
||
|
|
long long cpucycles_cortex_persecond(void)
|
||
|
|
{
|
||
|
|
while (!cyclespersec) cpucycles_cortex();
|
||
|
|
return cyclespersec * SCALE;
|
||
|
|
}
|