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/* Some utility functions around the free running clock on ARM. The clock is
* 32-bits wide, but we provide 64-bit wrapper functions to make it look
* similar to the read_tsc functions. On hardware we could actually make use
* of the timer overflow counter, but emulator doesn't emulate it. */
#include <minix/minlib.h>
#include <minix/sysutil.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <lib.h>
#include <assert.h>
#define MICROHZ 1000000ULL /* number of micros per second */
#define MICROSPERTICK(h) (MICROHZ/(h)) /* number of micros per HZ tick */
static u64_t Hz;
int
micro_delay(u32_t micros)
{
struct minix_kerninfo *minix_kerninfo;
u64_t start, delta, delta_end;
Hz = sys_hz();
minix_kerninfo = get_minix_kerninfo();
/* Start of delay. */
read_frclock_64(&start);
assert(minix_kerninfo->arm_frclock);
assert(minix_kerninfo->arm_frclock->hz);
delta_end = (minix_kerninfo->arm_frclock->hz * micros) / MICROHZ;
/* If we have to wait for at least one HZ tick, use the regular
* tickdelay first. Round downwards on purpose, so the average
* half-tick we wait short (depending on where in the current tick
* we call tickdelay). We can correct for both overhead of tickdelay
* itself and the short wait in the busywait later.
*/
if (micros >= MICROSPERTICK(Hz))
tickdelay(micros*Hz/MICROHZ);
/* Wait (the rest) of the delay time using busywait. */
do {
read_frclock_64(&delta);
} while (delta_frclock_64(start, delta) < delta_end);
return 0;
}
u32_t frclock_64_to_micros(u64_t tsc)
{
return (u32_t)
(tsc / (get_minix_kerninfo()->arm_frclock->hz / MICROHZ));
}
void
read_frclock(u32_t *frclk)
{
struct minix_kerninfo *minix_kerninfo = get_minix_kerninfo();
assert(frclk);
assert(minix_kerninfo->arm_frclock);
assert(minix_kerninfo->arm_frclock->tcrr);
*frclk = *(volatile u32_t *)((u8_t *)
minix_kerninfo->arm_frclock->tcrr);
}
u32_t
delta_frclock(u32_t base, u32_t cur)
{
u32_t delta;
if (cur < base) {
/* We have wrapped around, so delta is base to wrapping point
* plus starting point (0) to cur. This supports wrapping once
* only. */
delta = (UINT_MAX - base) + cur;
} else {
delta = cur - base;
}
return delta;
}
void
read_frclock_64(u64_t *frclk)
{
read_frclock((u32_t *) frclk);
}
u64_t
delta_frclock_64(u64_t base, u64_t cur)
{
return (u64_t) delta_frclock((u32_t) base, (u32_t) cur);
}
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