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more accurate calculation of the processor frequency

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This commit is contained in:
Stefan Lankes 2011-04-07 20:31:10 +02:00
parent 030243f200
commit e96a549349
1 changed files with 5 additions and 8 deletions
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13
arch/x86/kernel/processor.c
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@ -23,16 +23,10 @@
#include <metalsvm/processor.h>
#ifdef CONFIG_ROCKCREEK
#include <asm/RCCE_lib.h>
#else
/* disable optimization for the following functions */
uint32_t detect_cpu_frequency(void) __attribute__((optimize(0)));
#endif
static uint32_t cpu_freq = 0;
/* disable optimization for the following functions */
void udelay(uint32_t usecs) __attribute__((optimize(0)));
uint32_t detect_cpu_frequency(void)
{
#ifdef CONFIG_ROCKCREEK
@ -53,12 +47,14 @@ uint32_t detect_cpu_frequency(void)
/* wait for the next time slice */
while((ticks = get_clock_tick()) - old == 0)
;
HALT;
rmb();
start = rdtsc();
/* wait a second to determine the frequency */
while(get_clock_tick() - ticks < TIMER_FREQ)
;
HALT;
rmb();
end = rdtsc();
diff = end > start ? end - start : start - end;
@ -82,6 +78,7 @@ void udelay(uint32_t usecs)
uint64_t deadline = get_cpu_frequency() * usecs;
do {
rmb();
end = rdtsc();
diff = end > start ? end - start : start - end;
} while(diff < deadline);