rt-thread/bsp/x86/drivers/drv_timer.c

/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2021-07-16     JasonHu      first version
 */

#include <rthw.h>
#include <rtthread.h>
#include <rtconfig.h>

#include "board.h"

/* PIT （Programmable Interval Timer）8253/8254 可编程中断计时器 */

/*
Port 40h, 8253 Counter 0 Time of Day Clock (normally mode 3)
*/
#define PIT_COUNTER0    0x40

/*
Port 41h, 8253 Counter 1 RAM Refresh Counter (normally mode 2)
*/
#define PIT_COUNTER1    0x41

/*
Port 42h, 8253 Counter 2 Cassette and Speaker Functions
*/
#define PIT_COUNTER2    0x42

/*
Programmable interrupt timer, control word register:
Port 43h, 8253 Mode Control Register, data format:

    |7|6|5|4|3|2|1|0|  Mode Control Register
     | | | | | | | `---- 0=16 binary counter, 1=4 decade BCD counter
     | | | | `--------- counter mode bits
     | | `------------ read/write/latch format bits
     `--------------- counter select bits (also 8254 read back command)

Read Back Command Format  (8254 only)

    |7|6|5|4|3|2|1|0| Read Back Command (written to Mode Control Reg)
     | | | | | | | `--- must be zero
     | | | | | | `---- select counter 0
     | | | | | `----- select counter 1
     | | | | `------ select counter 2
     | | | `------- 0 = latch status of selected counters
     | | `-------- 0 = latch count of selected counters
     `----------- 11 = read back command

Read Back Command Status (8254 only, read from counter register)

    |7|6|5|4|3|2|1|0|  Read Back Command Status
     | | | | | | | `--- 0=16 binary counter, 1=4 decade BCD counter
     | | | | `-------- counter mode bits (see Mode Control Reg above)
     | | `----------- read/write/latch format (see Mode Control Reg)
     | `------------ 1=null count (no count set), 0=count available
     `------------- state of OUT pin (1=high, 0=low)
*/
#define PIT_CTRL    0x43

/* Mode Control Register */
enum ctrl_mode_bits
{
    /* Bits 76 Counter Select Bits */
    PIT_MODE_COUNTER_0 = (0),            /* 00  select counter 0 */
    PIT_MODE_COUNTER_1 = (1 << 6),            /* 01  select counter 1 */
    PIT_MODE_COUNTER_2 = (1 << 7),            /* 10  select counter 2 */
    PIT_MODE_READ_BACK = ((1 << 6) | (1 << 7)),     /* 11  read back command (8254 only, illegal on 8253, see below) */
    /* Bits 54  Read/Write/Latch Format Bits */
    PIT_MODE_LPCV = (0),                 /* 00  latch present counter value */
    PIT_MODE_MSB = (1 << 4),                  /* 01  read/write of MSB only */
    PIT_MODE_LSB = (1 << 5),                  /* 10  read/write of LSB only */
    PIT_MODE_MSB_LSB = ((1 << 4) | (1 << 5)),       /* 11  read/write LSB, followed by write of MSB */
    /* Bits 321  Counter Mode Bits */

    /*
    000  mode 0, interrupt on terminal count;  countdown, interrupt,
        then wait for a new mode or count; loading a new count in the
        middle of a count stops the countdown
    */
    PIT_MODE_0 = (0),
    /*
    001  mode 1, programmable one-shot; countdown with optional
        restart; reloading the counter will not affect the countdown
        until after the following trigger
    */
    PIT_MODE_1 = (1 << 1),
    /*
    010  mode 2, rate generator; generate one pulse after 'count' CLK
        cycles; output remains high until after the new countdown has
        begun; reloading the count mid-period does not take affect
        until after the period
    */
    PIT_MODE_2 = (1 << 2),
    /*
    011  mode 3, square wave rate generator; generate one pulse after
        'count' CLK cycles; output remains high until 1/2 of the next
        countdown; it does this by decrementing by 2 until zero, at
        which time it lowers the output signal, reloads the counter
        and counts down again until interrupting at 0; reloading the
        count mid-period does not take affect until after the period

    */
    PIT_MODE_3 = ((1 << 1) | (1 << 2)),
    /*
    100  mode 4, software triggered strobe; countdown with output high
        until counter zero;  at zero output goes low for one CLK
        period;  countdown is triggered by loading counter;  reloading
        counter takes effect on next CLK pulse

    */
    PIT_MODE_4 = (1 << 3),
    /*
    101  mode 5, hardware triggered strobe; countdown after triggering
        with output high until counter zero; at zero output goes low
        for one CLK period
    */
    PIT_MODE_5 = ((1 << 1) | (1 << 3)),

    /* Bits 0  Counter Mode Bits */
    PIT_MODE_BINARY = (0),       /* 0 0= 16 binary counter */
    PIT_MODE_BCD = (1),          /* 1 1= 4 decade BCD counter */
};

#define TIMER_FREQ     1193180  /* clock frequency */
#define COUNTER0_VALUE  (TIMER_FREQ / RT_TICK_PER_SECOND)

static void rt_hw_timer_isr(int vector, void *param)
{
    rt_tick_increase();
}

int rt_hw_timer_init(void)
{
    outb(PIT_CTRL, PIT_MODE_2 | PIT_MODE_MSB_LSB |
         PIT_MODE_COUNTER_0 | PIT_MODE_BINARY);
    outb(PIT_COUNTER0, (rt_uint8_t) (COUNTER0_VALUE & 0xff));
    outb(PIT_COUNTER0, (rt_uint8_t) (COUNTER0_VALUE >> 8) & 0xff);

    rt_hw_interrupt_install(IRQ0_CLOCK, rt_hw_timer_isr, RT_NULL, "tick");
    rt_hw_interrupt_umask(IRQ0_CLOCK);
    return 0;
}