Is it possible to read / access the cycle count register in userspace?
(I'm on a DM365)
I attempted to read the register with the following code - but the
application dies with an invalid instruction.
Regards
--
Kieran Bingham
<<< Code Segment cpu-cycles.c >>>
static inline void
ccnt_start(void)
{
__asm__ volatile ("mcr p15, 0, %0, c9, c12, 1" ::
"r"(1<<31));
}
static inline void ccnt_stop(void)
{
__asm__ volatile ("mcr p15, 0, %0, c9, c12, 2" :: "r"(1<<31));
}
static inline unsigned ccnt_read(void)
{
unsigned cc;
__asm__ volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r"(cc));
return cc;
}
static inline void ccnt_init(void)
{
ccnt_stop();
__asm__ volatile ("mcr p15, 0, %0, c9, c12, 0" :: "r"(5));
}
static inline void enable_user_pmon(void)
{
__asm__ volatile ("mov r0, #1");
__asm__ volatile ("mcr p15, 0, r0, c9, c14, 0");
}
#include <stdio.h>
#include <stdlib.h>
void main(void)
{
int start;
int stop;
enable_user_pmon();
ccnt_init();
start = ccnt_read();
ccnt_start();
usleep(1000);
stop = ccnt_read();
printf("CCNT Ran for %d cycles\n", stop - start);
}
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