1/* @title: Programmable Interval Timer */
2#pragma once
3#include <acpi/ioapic.h>
4#include <irq/irq.h>
5#include <stdbool.h>
6#include <stddef.h>
7#include <stdint.h>
8#include <time/time.h>
9#include <types/types.h>
10
11/* IO ports */
12#define PIT_PORT_CHANNEL0 0x40
13#define PIT_PORT_CHANNEL1 0x41
14#define PIT_PORT_CHANNEL2 0x42
15#define PIT_PORT_COMMAND 0x43
16
17#define PIT_PORT_CHANNEL(ch) ((uint16_t) (PIT_PORT_CHANNEL0 + (ch)))
18
19/* PIT Base Frequency (1.193182 MHz) */
20#define PIT_BASE_FREQUENCY_HZ 1193182ULL
21#define PIT_FREQUENCY 1193182ULL
22
23/*
24 * PIT Command Register (PIT_PORT_COMMAND) Bit Definitions
25 *
26 * Bit 7..6: Channel Selection
27 * Bit 5..4: Access / Operating Mode
28 * Bit 3..1: Operating Mode (0-5)
29 * Bit 0: BCD / Binary (0 = 16 bit binary, 1 = BCD)
30 */
31
32#define PIT_CMD_CHANNEL(ch) ((uint8_t) (((ch) & 0x3) << 6))
33#define PIT_CMD_CHANNEL0 0x00
34#define PIT_CMD_CHANNEL1 0x40
35#define PIT_CMD_CHANNEL2 0x80
36#define PIT_CMD_READBACK 0xC0
37
38#define PIT_CMD_ACCESS_LATCH 0x00 /* Latch count value command */
39#define PIT_CMD_ACCESS_LO 0x10 /* Low byte only */
40#define PIT_CMD_ACCESS_HI 0x20 /* High byte only */
41#define PIT_CMD_ACCESS_LOHI 0x30 /* Low byte then high byte (16 bit) */
42
43/* Operating Modes */
44#define PIT_CMD_MODE_ONESHOT 0x00
45#define PIT_CMD_MODE_HW_ONESHOT 0x02
46#define PIT_CMD_MODE_RATE_GEN 0x04
47#define PIT_CMD_MODE_SQUARE_WAVE 0x06
48#define PIT_CMD_MODE_SW_STROBE 0x08
49#define PIT_CMD_MODE_HW_STROBE 0x0A
50
51/* Binary / BCD */
52#define PIT_CMD_BINARY 0x00
53#define PIT_CMD_BCD 0x01
54
55#define PIT_DEFAULT_MODE 0x34
56#define PIT_DEFAULT_COUNT 0x4AF2
57#define PIT_CALIBRATION_MODE 0x30
58#define PIT_CALIBRATION_COUNT UINT16_MAX
59
60#define PIT_DIVISOR_MIN 1
61#define PIT_DIVISOR_MAX_COUNT UINT16_MAX
62#define PIT_DIVISOR_ROLLOVER_VAL 0 /* 0 is 65536 in binary mode */
63
64void pit_init(void);
65
66void pit_set_divisor(uint16_t divisor);
67void pit_set_frequency(freq_hz_t freq_hz);
68void pit_set_interval_ns(time_ns_t interval_ns);
69void pit_set_periodic_mode(uint16_t divisor);
70void pit_set_oneshot_mode(uint16_t divisor);
71void pit_wire_periodic_nmi(time_ns_t interval_ns);
72freq_hz_t pit_measure_tsc_freq(void);
73