systick.c

专业汽车级嵌入式操作系统OSEK的源代码

/*
 *  This provides a 1000Hz tick for the system.
 *
 *  NB At 1000Hz, a U32 will roll over in approx 50 days.
 *  Therefore a todo to get rid of this at some stage.
 *
 *  We're using TC0
 */

#include "aic.h"
#include "AT91SAM7.h"
#include "interrupts.h"
#include "systick.h"

#include "nxt_motors.h"
#include "nxt_avr.h"

extern volatile unsigned char gMakeRequest;

#define PIT_FREQ 1000		/* Hz */

#define LOW_PRIORITY_IRQ 10

static volatile U32 systick_sec;
static volatile U32 systick_sub_sec;
static volatile U32 systick_ms;

extern void systick_isr_entry(void);
extern void systick_low_priority_entry(void);

// Systick low priority
void
systick_low_priority_C(void)
{
  *AT91C_AIC_ICCR = (1 << LOW_PRIORITY_IRQ);
  gMakeRequest = 1;		// trigger Java tick request
  nxt_avr_1kHz_update();
  nxt_motor_1kHz_process();
}

// Called at 1000Hz
void
systick_isr_C(void)
{
  U32 status;

  /* Read status to confirm interrupt */
  status = *AT91C_PITC_PIVR;

//  systick_low_priority_C();

  systick_ms++;

  systick_sub_sec++;

  if (systick_sub_sec >= PIT_FREQ) {
    systick_sub_sec = 0;
    systick_sec++;
  }
  // Trigger low priority task
  *AT91C_AIC_ISCR = (1 << LOW_PRIORITY_IRQ);
}



U32
systick_get_ms(void)
{
  // We're using a 32-bitter and can assume that we
  // don't need to do any locking here.
  return systick_ms;
}


void
systick_wait_ms(U32 ms)
{
  volatile U32 final = ms + systick_ms;

  while (systick_ms < final) {
  }
}


void
systick_wait_ns(U32 ns)
{
  volatile x = (ns >> 7) + 1;

  while (x) {
    x--;
  }
}

void
systick_init(void)
{
  int i_state = interrupts_get_and_disable();

  aic_mask_off(LOW_PRIORITY_IRQ);
  aic_set_vector(LOW_PRIORITY_IRQ, (1 << 5) /* positive internal edge */ |
		 AIC_INT_LEVEL_LOW, (U32) systick_low_priority_entry);
  aic_mask_on(LOW_PRIORITY_IRQ);

  aic_mask_off(AT91C_PERIPHERAL_ID_SYSIRQ);
  aic_set_vector(AT91C_PERIPHERAL_ID_SYSIRQ, (1 << 5) /* positive internal edge */ |
		 AIC_INT_LEVEL_NORMAL, (U32) systick_isr_entry);

  aic_mask_on(AT91C_PERIPHERAL_ID_SYSIRQ);
  *AT91C_PITC_PIMR = ((CLOCK_FREQUENCY / 16 / PIT_FREQ) - 1) | 0x03000000;	/* Enable, enable interrupts */

  if (i_state)
    interrupts_enable();
}

void
systick_get_time(U32 *sec, U32 *usec)
{
  int istate = interrupts_get_and_disable();

  if (sec)
    *sec = systick_sec;
  if (usec)
    *usec = systick_sub_sec * (1000000 / PIT_FREQ);

  if (istate)
    interrupts_enable();
}


static U32 test_counter;
void
systick_test(void)
{
  while (1) {
    test_counter++;
    systick_wait_ms(2000);
  }
}