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fix(timer): removing cascade when TIM aleady enabled shouldn't reset counter

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-11-20 19:13:49 -04:00
parent 4ed4f8e143
commit c5cf471912
1 changed files with 29 additions and 13 deletions
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42
src/core/bus/timer.zig
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@ -150,21 +150,36 @@ fn Timer(comptime id: u2) type {
pub fn setTimcntH(self: *Self, halfword: u16) void {
const new = TimerControl{ .raw = halfword };
// If Timer happens to be enabled, It will either be resheduled or disabled
self.sched.removeScheduledEvent(.{ .TimerOverflow = id });
if (self.cnt.enabled.read()) {
// timer was already enabled
if (self.cnt.enabled.read() and (new.cascade.read() or !new.enabled.read())) {
// Either through the cascade bit or the enable bit, the timer has effectively been disabled
// The Counter should hold whatever value it should have been at when it was disabled
self._counter +%= @truncate(u16, (self.sched.now() - self._start_timestamp) / self.frequency());
// If enabled falling edge or cascade falling edge, timer is paused
if (!new.enabled.read() or (!self.cnt.cascade.read() and new.cascade.read())) {
self.sched.removeScheduledEvent(.{ .TimerOverflow = id });
// Counter should hold the value it stopped at meaning we have to calculate it now
self._counter +%= @truncate(u16, (self.sched.now() - self._start_timestamp) / self.frequency());
}
// the timer has always been enabled, but the cascade bit which was blocking the timer has been unset
if (new.enabled.read() and (self.cnt.cascade.read() and !new.cascade.read())) {
// we want to reschedule the timer event, however we won't reload the counter.
// the invariant here is that self._counter holds the already calculated paused value
self.rescheduleTimerExpire(0);
}
} else {
// the timer was previously disabeld
if (new.enabled.read()) {
// timer should start counting (with a reloaded counter value)
self._counter = self._reload;
// if cascade happens to be set, the timer doesn't actually do anything though
if (!new.cascade.read()) self.rescheduleTimerExpire(0);
}
}
// The counter is only reloaded on the rising edge of the enable bit
if (!self.cnt.enabled.read() and new.enabled.read()) self._counter = self._reload;
// If Timer is enabled and we're not cascading, we need to schedule an overflow event
if (new.enabled.read() and !new.cascade.read()) self.rescheduleTimerExpire(0);
self.cnt.raw = halfword;
}
@ -202,7 +217,8 @@ fn Timer(comptime id: u2) type {
}
// Reschedule Timer if we're not cascading
if (!self.cnt.cascade.read()) {
// TIM0 cascade value is N/A
if (id == 0 or !self.cnt.cascade.read()) {
self._counter = self._reload;
self.rescheduleTimerExpire(late);
}