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Minimal timer period of 100us introduced in r244758 is overkill. While

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original 2us are indeed not enough, 3us are working quite well on my tests.
To be more safe set minimal period to 5us and to be even more safe replicate
here from HPET mechanism of rereading counter after programming comparator.

This change allows to handle 30K of short nanosleep() calls per second on
Raspberry Pi instead of just 8K before.

Discussed with:	gonzo
This commit is contained in:
Alexander Motin 2013-03-21 15:42:41 +00:00
parent d071a6fa33
commit 359b47db97
1 changed files with 11 additions and 4 deletions
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15
sys/arm/broadcom/bcm2835/bcm2835_systimer.c
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@ -55,7 +55,7 @@ __FBSDID("$FreeBSD$");
#define DEFAULT_TIMER 3
#define DEFAULT_FREQUENCY 1000000
#define MIN_PERIOD 100LLU
#define MIN_PERIOD 5LLU
#define SYSTIMER_CS 0x00
#define SYSTIMER_CLO 0x04
@ -121,7 +121,7 @@ static int
bcm_systimer_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
{
struct systimer *st = et->et_priv;
uint32_t clo;
uint32_t clo, clo1;
uint32_t count;
register_t s;
@ -131,12 +131,19 @@ bcm_systimer_start(struct eventtimer *et, sbintime_t first, sbintime_t period)
s = intr_disable();
clo = bcm_systimer_tc_read_4(SYSTIMER_CLO);
restart:
clo += count;
/*
* Clear pending interrupts
*/
bcm_systimer_tc_write_4(SYSTIMER_CS, (1 << st->index));
bcm_systimer_tc_write_4(SYSTIMER_C0 + st->index*4, clo);
clo1 = bcm_systimer_tc_read_4(SYSTIMER_CLO);
if ((int32_t)(clo1 - clo) >= 0) {
count *= 2;
clo = clo1;
goto restart;
}
st->enabled = 1;
intr_restore(s);
@ -236,9 +243,9 @@ bcm_systimer_attach(device_t dev)
sc->st[DEFAULT_TIMER].et.et_quality = 1000;
sc->st[DEFAULT_TIMER].et.et_frequency = sc->sysclk_freq;
sc->st[DEFAULT_TIMER].et.et_min_period =
(MIN_PERIOD << 32) / sc->st[DEFAULT_TIMER].et.et_frequency;
(MIN_PERIOD << 32) / sc->st[DEFAULT_TIMER].et.et_frequency + 1;
sc->st[DEFAULT_TIMER].et.et_max_period =
(0xfffffffeLLU << 32) / sc->st[DEFAULT_TIMER].et.et_frequency;
(0x7ffffffeLLU << 32) / sc->st[DEFAULT_TIMER].et.et_frequency;
sc->st[DEFAULT_TIMER].et.et_start = bcm_systimer_start;
sc->st[DEFAULT_TIMER].et.et_stop = bcm_systimer_stop;
sc->st[DEFAULT_TIMER].et.et_priv = &sc->st[DEFAULT_TIMER];