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Kernel: Do timekeeping manually instead of asking the RTC all the time.

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This introduces a tiny amount of timer drift which I will have to fix
somehow eventually, but it's a huge improvement in timing consistency
as we no longer suddenly jump from e.g 10:45:49.123 to 10:45:50.000.
This commit is contained in:
Andreas Kling 2019-03-25 02:06:57 +01:00
parent 20f7d7ec67
commit ab11f42094
5 changed files with 34 additions and 21 deletions
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20
Kernel/i8253.cpp
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@ -57,26 +57,34 @@ asm(
#define BASE_FREQUENCY 1193182
static dword s_ticks_since_boot;
static dword s_ticks_this_second;
static dword s_seconds_since_boot;
void timer_interrupt_handler(RegisterDump& regs)
{
IRQHandlerScope scope(IRQ_TIMER);
++s_ticks_since_boot;
if (++s_ticks_this_second >= TICKS_PER_SECOND) {
// FIXME: Synchronize with the RTC somehow to prevent drifting apart.
++s_seconds_since_boot;
s_ticks_this_second = 0;
}
Scheduler::timer_tick(regs);
}
namespace PIT {
dword ticks_since_boot()
dword ticks_this_second()
{
return s_ticks_since_boot;
return s_ticks_this_second;
}
dword seconds_since_boot()
{
return s_seconds_since_boot;
}
void initialize()
{
s_ticks_since_boot = 0;
word timer_reload;
IO::out8(PIT_CTL, TIMER0_SELECT | WRITE_WORD | MODE_SQUARE_WAVE);