mirror of
https://github.com/RGBCube/serenity
synced 2025-10-31 02:12:45 +00:00
ab11f42094
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.
104 lines
2.2 KiB
C++
104 lines
2.2 KiB
C++
#include "i8253.h"
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#include "i386.h"
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#include "IO.h"
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#include "PIC.h"
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#include "Scheduler.h"
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#define IRQ_TIMER 0
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extern "C" void timer_interrupt_entry();
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extern "C" void timer_interrupt_handler(RegisterDump&);
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asm(
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".globl timer_interrupt_entry \n"
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"timer_interrupt_entry: \n"
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" pusha\n"
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" pushw %ds\n"
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" pushw %es\n"
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" pushw %fs\n"
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" pushw %gs\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" popw %ds\n"
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" popw %es\n"
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" popw %fs\n"
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" popw %gs\n"
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" mov %esp, %eax\n"
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" call timer_interrupt_handler\n"
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" popw %gs\n"
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" popw %gs\n"
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" popw %fs\n"
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" popw %es\n"
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" popw %ds\n"
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" popa\n"
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" iret\n"
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);
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/* Timer related ports */
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#define TIMER0_CTL 0x40
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#define TIMER1_CTL 0x41
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#define TIMER2_CTL 0x42
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#define PIT_CTL 0x43
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/* Building blocks for PIT_CTL */
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#define TIMER0_SELECT 0x00
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#define TIMER1_SELECT 0x40
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#define TIMER2_SELECT 0x80
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#define MODE_COUNTDOWN 0x00
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#define MODE_ONESHOT 0x02
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#define MODE_RATE 0x04
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#define MODE_SQUARE_WAVE 0x06
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#define WRITE_WORD 0x30
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#define BASE_FREQUENCY 1193182
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static dword s_ticks_this_second;
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static dword s_seconds_since_boot;
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void timer_interrupt_handler(RegisterDump& regs)
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{
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IRQHandlerScope scope(IRQ_TIMER);
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if (++s_ticks_this_second >= TICKS_PER_SECOND) {
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// FIXME: Synchronize with the RTC somehow to prevent drifting apart.
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++s_seconds_since_boot;
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s_ticks_this_second = 0;
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}
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Scheduler::timer_tick(regs);
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}
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namespace PIT {
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dword ticks_this_second()
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{
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return s_ticks_this_second;
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}
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dword seconds_since_boot()
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{
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return s_seconds_since_boot;
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}
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void initialize()
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{
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word timer_reload;
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IO::out8(PIT_CTL, TIMER0_SELECT | WRITE_WORD | MODE_SQUARE_WAVE);
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timer_reload = (BASE_FREQUENCY / TICKS_PER_SECOND);
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kprintf("PIT: %u Hz, square wave (%x)\n", TICKS_PER_SECOND, timer_reload);
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IO::out8(TIMER0_CTL, LSB(timer_reload));
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IO::out8(TIMER0_CTL, MSB(timer_reload));
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register_interrupt_handler(IRQ_VECTOR_BASE + IRQ_TIMER, timer_interrupt_entry);
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PIC::enable(IRQ_TIMER);
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}
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}
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