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libsys: tsc_to_micros support for large TSC delta values

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This commit is contained in:
David van Moolenbroek 2010-09-23 09:26:42 +00:00
parent 62aba4396e
commit adbc4e4ea7
1 changed files with 35 additions and 12 deletions
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47
lib/libsys/tsc_util.c
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@ -6,6 +6,7 @@
#include <minix/u64.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/minlib.h>
#include "sysutil.h"
@ -93,22 +94,44 @@ micro_delay(u32_t micros)
u32_t tsc_64_to_micros(u64_t tsc)
{
return tsc_to_micros(ex64lo(tsc), ex64hi(tsc));
u64_t tmp;
u32_t imv;
CALIBRATE;
/* Various formulas provide various levels of accuracy depending on
* what still fits in a 64-bit number.
*/
if (ex64hi(tsc) != 0) {
if (ex64hi(tsc) < ULONG_MAX) {
tmp = mul64u(ex64hi(tsc) + 1, MICROHZ);
if (ex64hi(tmp) == 0) {
imv = div64u(mul64(tsc, cvu64(MICROHZ)),
calib_tsc);
tmp = mul64u(imv, CALIBRATE_TICKS(Hz));
if (ex64hi(tmp) == 0) {
/* Mid accuracy. */
return ex64lo(tmp) / Hz;
}
}
}
/* Low accuracy for large numbers. */
return div64u(mul64u(div64u(tsc, calib_tsc),
MICROHZ * CALIBRATE_TICKS(Hz)), Hz);
}
/* High accuracy for small numbers (the common case). */
return div64u(mul64u(ex64lo(tsc), MICROHZ * CALIBRATE_TICKS(Hz)),
calib_tsc) / Hz;
}
u32_t tsc_to_micros(u32_t low, u32_t high)
{
u32_t micros;
if(high) {
return 0;
}
CALIBRATE;
micros = (div64u(mul64u(low, MICROHZ * CALIBRATE_TICKS(Hz)),
calib_tsc)/Hz);
return micros;
return tsc_64_to_micros(make64(low, high));
}
u32_t tsc_get_khz(void)