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Fix event timer on Raspberry Pi

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- Disable interrupt when updating compare value in order to
   make this operation atomical

- Increase minimum period for event timer. Systimer on BCM2835
    is compare timer, so if minimum period is too small it might
    be less then fraction of time between "read current value" and
    "set compare timer" operations. It means that when timer is armed
    actual counter value is more then compare value and it will take
    whole cycle (~32sec for 1MHz timer) to fire interrupt.

Submitted by:	Daisuke Aoyama <aoyama at peach.ne.jp>
This commit is contained in:
Oleksandr Tymoshenko 2012-12-28 01:38:43 +00:00
parent 5625bb0c36
commit 0c093a7055
1 changed files with 16 additions and 2 deletions
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18
sys/arm/broadcom/bcm2835/bcm2835_systimer.c
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@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
#define DEFAULT_TIMER 3
#define DEFAULT_FREQUENCY 1000000
#define MIN_PERIOD 100LLU
#define SYSTIMER_CS 0x00
#define SYSTIMER_CLO 0x04
@ -123,17 +124,24 @@ bcm_systimer_start(struct eventtimer *et, struct bintime *first,
struct systimer *st = et->et_priv;
uint32_t clo;
uint32_t count;
register_t s;
if (first != NULL) {
st->enabled = 1;
count = (st->et.et_frequency * (first->frac >> 32)) >> 32;
if (first->sec != 0)
count += st->et.et_frequency * first->sec;
s = intr_disable();
clo = bcm_systimer_tc_read_4(SYSTIMER_CLO);
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);
st->enabled = 1;
intr_restore(s);
return (0);
}
@ -154,7 +162,13 @@ static int
bcm_systimer_intr(void *arg)
{
struct systimer *st = (struct systimer *)arg;
uint32_t cs;
cs = bcm_systimer_tc_read_4(SYSTIMER_CS);
if ((cs & (1 << st->index)) == 0)
return (FILTER_STRAY);
/* ACK interrupt */
bcm_systimer_tc_write_4(SYSTIMER_CS, (1 << st->index));
if (st->enabled) {
if (st->et.et_active) {
@ -226,7 +240,7 @@ bcm_systimer_attach(device_t dev)
sc->st[DEFAULT_TIMER].et.et_frequency = sc->sysclk_freq;
sc->st[DEFAULT_TIMER].et.et_min_period.sec = 0;
sc->st[DEFAULT_TIMER].et.et_min_period.frac =
((0x00000002LLU << 32) / sc->st[DEFAULT_TIMER].et.et_frequency) << 32;
((MIN_PERIOD << 32) / sc->st[DEFAULT_TIMER].et.et_frequency) << 32;
sc->st[DEFAULT_TIMER].et.et_max_period.sec = 0xfffffff0U / sc->st[DEFAULT_TIMER].et.et_frequency;
sc->st[DEFAULT_TIMER].et.et_max_period.frac =
((0xfffffffeLLU << 32) / sc->st[DEFAULT_TIMER].et.et_frequency) << 32;