50 lines
1.1 KiB
C++
50 lines
1.1 KiB
C++
#include <pit.h>
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#include <common.h>
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#include <string_utils.h>
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#include <pic.h>
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#include <serial.h>
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static inline void outb(UINT16 port, UINT8 val) {
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ASM("outb %0, %1" : : "a"(val), "Nd"(port));
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}
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static volatile UINT64 g_ticks = 0;
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static timer_callback_t g_tick_handler = NULL;
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extern "C" void pit_irq_handler(void) {
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g_ticks++;
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if (g_tick_handler) {
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g_tick_handler();
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}
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}
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void pit_init(void) {
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serial_write("PIT: initializing channel 0 at ");
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serial_write_hex(PIT_TICK_HZ);
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serial_write(" Hz\n");
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UINT32 divisor = PIT_BASE_FREQ / PIT_TICK_HZ;
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// 命令字节：通道 0，低/高字节，速率生成器，二进制
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outb(PIT_COMMAND_PORT, 0x36);
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// 发送除数（先低字节后高字节）
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outb(PIT_CHANNEL0_DATA, (UINT8)(divisor & 0xFF));
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outb(PIT_CHANNEL0_DATA, (UINT8)((divisor >> 8) & 0xFF));
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// 取消屏蔽 IRQ 0（定时器）
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pic_unmask_irq(0);
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serial_write("PIT: divisor = ");
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serial_write_hex(divisor);
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serial_write("\n");
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}
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void pit_set_tick_handler(timer_callback_t handler) {
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g_tick_handler = handler;
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}
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UINT64 pit_get_ticks(void) {
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return g_ticks;
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}
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