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#include "pit.h"
#define PIT_IO_CHANNEL_0 0x40
#define PIT_IO_MODE_COMMAND 0x43
u64 clock_num_ms_ticks = 0;
u64 pit_counter = 0;
u16 hertz;
u64 pit_num_ms(void) {
return clock_num_ms_ticks;
}
u16 read_pit_count(void) {
u16 count = 0;
outb(PIT_IO_MODE_COMMAND, 0x0 /*0b00000000*/);
count = inb(PIT_IO_CHANNEL_0);
count |= inb(PIT_IO_CHANNEL_0) << 8;
return count;
}
void set_pit_count(u16 hertz) {
u16 divisor = 1193180 / hertz;
/*
* 0b00110110
* ^^
* channel - 0
* ^^
* r/w mode - LSB then MSB
* ^^^
* mode - 3 Square Wave Mode
* ^
* BCD - no
*/
outb(PIT_IO_MODE_COMMAND, 0x36 /*0b00110110*/);
outb(PIT_IO_CHANNEL_0, divisor & 0xFF);
outb(PIT_IO_CHANNEL_0, (divisor & 0xFF00) >> 8);
}
__attribute__((interrupt)) void int_clock(registers_t *regs) {
process_t *p = get_current_task();
if (p) {
// FIXME: For some reason eflags is the esp? I have read the
// manual multilpe times and still can't figure out why.
if (regs->eflags <= 0x90000000 && regs->eflags) {
p->useresp = regs->eflags;
}
}
outb(0x20, 0x20);
pit_counter++;
if (pit_counter >= hertz / 1000) {
pit_counter = 0;
clock_num_ms_ticks++;
}
switch_task(1);
}
void pit_install(void) {
install_handler(int_clock, INT_32_INTERRUPT_GATE(0x3), 0x20);
}
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