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/*
* Copyright (c) 2017 Richard Braun.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <lib/macros.h>
#include "cpu.h"
#include "i8254.h"
#include "io.h"
#include "thread.h"
#define I8254_FREQ 1193182
#define I8254_PORT_CHANNEL0 0x40
#define I8254_PORT_MODE 0x43
#define I8254_CONTROL_BINARY 0x00
#define I8254_CONTROL_RATE_GEN 0x04
#define I8254_CONTROL_RW_LSB 0x10
#define I8254_CONTROL_RW_MSB 0x20
#define I8254_CONTROL_COUNTER0 0x00
#define I8254_INITIAL_COUNT DIV_CEIL(I8254_FREQ, THREAD_SCHED_FREQ)
#define I8254_IRQ 0
static void
i8254_irq_handler(void *arg)
{
(void)arg;
thread_report_tick();
}
void
i8254_setup(void)
{
uint16_t value;
/*
* Program the timer to raise an interrupt at the scheduling frequency.
*/
io_write(I8254_PORT_MODE, I8254_CONTROL_COUNTER0
| I8254_CONTROL_RW_MSB
| I8254_CONTROL_RW_LSB
| I8254_CONTROL_RATE_GEN
| I8254_CONTROL_BINARY);
value = I8254_INITIAL_COUNT;
io_write(I8254_PORT_CHANNEL0, value & 0xff);
io_write(I8254_PORT_CHANNEL0, value >> 8);
cpu_irq_register(I8254_IRQ, i8254_irq_handler, NULL);
}
|