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#include "pit8253.h"
#include "pic8259.h"
#include "port.h"
#include "kprint.h"
#include <stdatomic.h>
#define PIT8253_DATA0 0x40
#define PIT8253_CMD 0x43
#define SEL_CHANNEL0 0x0
#define ACC_LOHI 0x30
#define MODE_RATE 0x04
#define BIN_COUNT 0x0
#define CONFIG_CHANNEL_0 (SEL_CHANNEL0|ACC_LOHI|MODE_RATE|BIN_COUNT)
#define PIT_IRQ 0
#define PIT_HZ 1193182U
#define PIT_HZ_MIN (PIT_HZ/0xffff)
static void pit8253_set_divisor(uint16_t divisor);
static volatile atomic_uint_fast64_t count = 0;
static uint16_t divisor = 0;
const struct timer_source pit8253_timer_source =
{
"pit8253",
pit8253_init,
pit8253_start,
pit8253_stop,
pit8253_set_frequency,
pit8253_get_frequency,
pit8253_nanoseconds_elapsed,
pit8253_nanoseconds_delta
};
int pit8253_callback(uint8_t irq)
{
(void)irq;
count++;
return 0;
}
void pit8253_init(void)
{
pic8259_irq_install(PIT_IRQ, pit8253_callback);
}
void pit8253_start(void)
{
pic8259_irq_unmask(PIT_IRQ);
}
void pit8253_stop(void)
{
pic8259_irq_mask(PIT_IRQ);
}
void pit8253_set_frequency(uint32_t frequency)
{
uint32_t d = PIT_HZ / frequency;
if (d > UINT16_MAX)
{
kprintf("warning: %uHz is too slow for 8253 pit\n", PIT_HZ/d);
d = UINT16_MAX;
kprintf("warning: set timer to minimum frequency\n");
}
pit8253_set_divisor(d);
}
uint32_t pit8253_get_frequency(void)
{
return PIT_HZ/divisor;
}
uint64_t pit8253_nanoseconds_elapsed(void)
{
return pit8253_nanoseconds_delta() * atomic_load(&count);
}
uint64_t pit8253_nanoseconds_delta(void)
{
return (TIMER_NANOSECOND * divisor)/PIT_HZ;
}
static void pit8253_set_divisor(uint16_t d)
{
outb(PIT8253_CMD, CONFIG_CHANNEL_0);
outb(PIT8253_DATA0, (uint8_t)d);
outb(PIT8253_DATA0, (uint8_t)(d >> 8));
divisor = d;
}
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