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* Copyright (c) 2001-2004 Jakub Jermar
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* - The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* @brief i8254 chip driver.
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* Low level time functions.
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#include <arch/types.h>
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#include <time/clock.h>
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#include <time/delay.h>
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#include <arch/cycle.h>
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#include <arch/interrupt.h>
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#include <arch/drivers/i8259.h>
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#include <arch/drivers/i8254.h>
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#include <arch/cpuid.h>
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#include <time/delay.h>
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#include <ddi/device.h>
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#define CLK_PORT1 ((ioport8_t *)0x40)
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#define CLK_PORT4 ((ioport8_t *)0x43)
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#define CLK_CONST 1193180
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#define MAGIC_NUMBER 1194
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static irq_t i8254_irq;
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static irq_ownership_t i8254_claim(irq_t *irq)
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static void i8254_irq_handler(irq_t *irq)
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* This IRQ is responsible for kernel preemption.
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* Nevertheless, we are now holding a spinlock which prevents
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* preemption. For this particular IRQ, we don't need the
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* lock. We just release it, call clock() and then reacquire it again.
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spinlock_unlock(&irq->lock);
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spinlock_lock(&irq->lock);
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irq_initialize(&i8254_irq);
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i8254_irq.preack = true;
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i8254_irq.devno = device_assign_devno();
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i8254_irq.inr = IRQ_CLK;
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i8254_irq.claim = i8254_claim;
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i8254_irq.handler = i8254_irq_handler;
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irq_register(&i8254_irq);
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i8254_normal_operation();
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void i8254_normal_operation(void)
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pio_write_8(CLK_PORT4, 0x36);
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pic_disable_irqs(1 << IRQ_CLK);
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pio_write_8(CLK_PORT1, (CLK_CONST / HZ) & 0xf);
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pio_write_8(CLK_PORT1, (CLK_CONST / HZ) >> 8);
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pic_enable_irqs(1 << IRQ_CLK);
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void i8254_calibrate_delay_loop(void)
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uint32_t t1, t2, o1, o2;
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* One-shot timer. Count-down from 0xffff at 1193180Hz
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* MAGIC_NUMBER is the magic value for 1ms.
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pio_write_8(CLK_PORT4, 0x30);
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pio_write_8(CLK_PORT1, 0xff);
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pio_write_8(CLK_PORT1, 0xff);
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/* will read both status and count */
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pio_write_8(CLK_PORT4, 0xc2);
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not_ok = (uint8_t) ((pio_read_8(CLK_PORT1) >> 6) & 1);
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t1 = pio_read_8(CLK_PORT1);
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t1 |= pio_read_8(CLK_PORT1) << 8;
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asm_delay_loop(LOOPS);
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pio_write_8(CLK_PORT4, 0xd2);
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t2 = pio_read_8(CLK_PORT1);
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t2 |= pio_read_8(CLK_PORT1) << 8;
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* We want to determine the overhead of the calibrating mechanism.
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pio_write_8(CLK_PORT4, 0xd2);
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o1 = pio_read_8(CLK_PORT1);
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o1 |= pio_read_8(CLK_PORT1) << 8;
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asm_fake_loop(LOOPS);
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pio_write_8(CLK_PORT4, 0xd2);
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o2 = pio_read_8(CLK_PORT1);
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o2 |= pio_read_8(CLK_PORT1) << 8;
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CPU->delay_loop_const =
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((MAGIC_NUMBER * LOOPS) / 1000) / ((t1 - t2) - (o1 - o2)) +
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(((MAGIC_NUMBER * LOOPS) / 1000) % ((t1 - t2) - (o1 - o2)) ? 1 : 0);
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CPU->frequency_mhz = (clk2 - clk1) >> SHIFT;