//------------------------------------------------------------------------------
//
// Function: OALTimerReduceSysTick
//
UINT32 OALTimerReduceSysTick(UINT32 count, UINT32 margin)
{
UINT32 rc, edge, compare;
edge = OALTimerGetCount();
compare = OALTimerGetCompare();
// Update the countdown value
OALTimerSetCompare(count);
if (edge > margin)
{
// We are far enough from the interrupt that we should return the
// number of ticks that would have occurred since the last tick based
// on the new number of counts per tick. We will avoid the interrupt and
// just start fresh.
rc = (compare - edge) / count;
OALTimerSetCount(count);
}
else {
// We are close enough to the next interrupt that we will let the
// interrupt occur. We will also return the number of counts that would
// have happened since the last tick based on the new number of counts
// per tick, but we will subtract one because another is just about to
// happen.
rc = (compare / count) - 1;
}
return rc;
}
//------------------------------------------------------------------------------
//
// Function: OALTimerExtendSysTick
//
VOID OALTimerExtendSysTick(UINT32 count, UINT32 margin, UINT32 offset)
{
UINT32 compare, edge;
edge = OALTimerGetCount();
compare = OALTimerGetCompare();
if (edge > ((count - compare) + margin + offset))
{
// We are far enough away from the interrupt that we should just
// increase the time it will take to hit the next interrupt taking into
// account the offset provided.
OALTimerSetCount(edge - (count - offset - compare));
}
OALTimerSetCompare(count);
}
//------------------------------------------------------------------------------
//
// Function: OALTimerRecharge
//
// This function recharge count/compare timer. In case that we are late more
// than margin value we will use count as new counter base. Under
// normal conditions previous compare value stored in global variable is used.
// Using global variable instead reading compare register allows compensate
// offset when we reduce system tick to value which can cause hazard.
//
VOID OALTimerRecharge(UINT32 period, UINT32 margin)
{
UINT32 count;
count = OALTimerGetCount();
// Check if recharge was called in required margin
if ((INT32)(count - OALTimerGetCompare() - margin) < 0) {
// Yes, base new period on previous (no shift)
g_timer.base = g_timer.compare;
g_timer.compare += period;
} else {
// No, base new period on actual counter value (shift)
g_timer.base = count;
g_timer.compare = g_timer.base + period;
}
OALTimerSetCompare(g_timer.compare);
}
//------------------------------------------------------------------------------
//
// Function: OALTimerCountsSinceSysTick
//
INT32 OALTimerCountsSinceSysTick()
{
return OALTimerGetCompare() - OALTimerGetCount();
}
