source: mainline/kernel/arch/ia32/src/drivers/i8254.c@ 2a103b5

/*
 * Copyright (c) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup kernel_ia32
 * @{
 */
/**
 * @file
 * @brief i8254 chip driver.
 *
 * Low level time functions.
 */

#include <stdint.h>
#include <time/clock.h>
#include <time/delay.h>
#include <arch/cycle.h>
#include <arch/interrupt.h>
#include <genarch/drivers/i8259/i8259.h>
#include <arch/drivers/i8254.h>
#include <cpu.h>
#include <config.h>
#include <arch/pm.h>
#include <arch/asm.h>
#include <arch/cpuid.h>
#include <arch.h>
#include <ddi/irq.h>

#define CLK_PORT1  ((ioport8_t *) 0x40U)
#define CLK_PORT4  ((ioport8_t *) 0x43U)

#define CLK_CONST     1193180
#define MAGIC_NUMBER  1194

#define LOOPS  150000
#define SHIFT  11

static irq_t i8254_irq;

static irq_ownership_t i8254_claim(irq_t *irq)
{
        return IRQ_ACCEPT;
}

static void i8254_irq_handler(irq_t *irq)
{
        /*
         * This IRQ is responsible for kernel preemption.
         * Nevertheless, we are now holding a spinlock which prevents
         * preemption. For this particular IRQ, we don't need the
         * lock. We just release it, call clock() and then reacquire it again.
         */
        irq_spinlock_unlock(&irq->lock, false);
        clock();
        irq_spinlock_lock(&irq->lock, false);
}

void i8254_init(void)
{
        irq_initialize(&i8254_irq);
        i8254_irq.preack = true;
        i8254_irq.inr = IRQ_CLK;
        i8254_irq.claim = i8254_claim;
        i8254_irq.handler = i8254_irq_handler;
        irq_register(&i8254_irq);

        i8254_normal_operation();
}

void i8254_normal_operation(void)
{
        pio_write_8(CLK_PORT4, 0x36);
        i8259_disable_irqs(1 << IRQ_CLK);
        pio_write_8(CLK_PORT1, (CLK_CONST / HZ) & 0xf);
        pio_write_8(CLK_PORT1, (CLK_CONST / HZ) >> 8);
        i8259_enable_irqs(1 << IRQ_CLK);
}

void i8254_calibrate_delay_loop(void)
{
        /*
         * One-shot timer. Count-down from 0xffff at 1193180Hz
         * MAGIC_NUMBER is the magic value for 1ms.
         */
        pio_write_8(CLK_PORT4, 0x30);
        pio_write_8(CLK_PORT1, 0xff);
        pio_write_8(CLK_PORT1, 0xff);

        uint8_t not_ok;
        uint32_t t1;
        uint32_t t2;

        do {
                /* will read both status and count */
                pio_write_8(CLK_PORT4, 0xc2);
                not_ok = (uint8_t) ((pio_read_8(CLK_PORT1) >> 6) & 1);
                t1 = pio_read_8(CLK_PORT1);
                t1 |= pio_read_8(CLK_PORT1) << 8;
        } while (not_ok);

        asm_delay_loop(LOOPS);

        pio_write_8(CLK_PORT4, 0xd2);
        t2 = pio_read_8(CLK_PORT1);
        t2 |= pio_read_8(CLK_PORT1) << 8;

        /*
         * We want to determine the overhead of the calibrating mechanism.
         */
        pio_write_8(CLK_PORT4, 0xd2);
        uint32_t o1 = pio_read_8(CLK_PORT1);
        o1 |= pio_read_8(CLK_PORT1) << 8;

        asm_fake_loop(LOOPS);

        pio_write_8(CLK_PORT4, 0xd2);
        uint32_t o2 = pio_read_8(CLK_PORT1);
        o2 |= pio_read_8(CLK_PORT1) << 8;

        uint32_t delta = (t1 - t2) - (o1 - o2);
        if (!delta)
                delta = 1;

        CPU->delay_loop_const =
            ((MAGIC_NUMBER * LOOPS) / 1000) / delta +
            (((MAGIC_NUMBER * LOOPS) / 1000) % delta ? 1 : 0);

        uint64_t clk1 = get_cycle();
        delay(1 << SHIFT);
        uint64_t clk2 = get_cycle();

        CPU->frequency_mhz = (clk2 - clk1) >> SHIFT;

        return;
}

/** @}
 */