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81 lines
3.2 KiB
C
81 lines
3.2 KiB
C
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/*
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* Copyright (C) 2015, Intel Corporation. All rights reserved.
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*
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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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* are met:
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* 1. 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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* 2. 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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*
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* 3. Neither the name of the copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <math.h>
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#include "pit.h"
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#include "helpers.h"
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#include "interrupt.h"
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/* PCs usually provide an 8254 PIT chip with maximum clock of 1.193182 MHz. */
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#define PIT_CONTROL_PORT 0x43
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#define PIT_COUNTER0_PORT 0x40
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#define PIT_CLOCK_FREQUENCY 1193182
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static pit_int_callback interrupt_cb;
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static void
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pit_int_handler(void)
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{
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interrupt_cb();
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/* FIXME: Add a pic_send_eoi() API or similar and call it here. */
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outb(0x20, 0x20); /* master PIC */
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}
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/*---------------------------------------------------------------------------*/
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void
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pit_init(uint32_t ticks_rate, pit_int_callback cb)
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{
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/* FIXME: Call some PIC API to get the current offset and then add to its default IRQ number (0). */
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SET_INTERRUPT_HANDLER(32, 0, pit_int_handler);
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interrupt_cb = cb;
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/* Calculate the 16bit divisor that can provide the chosen clock tick rate
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* (CLOCK_CONF_SECOND in contiki-conf.h). For reference --> tick rate = clock frequency / divisor.
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* If we provide an odd divisor to the Square Wave generator (Mode 3) of
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* the Counter0, the duty cycle won't be exactly 50%, so we always round
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* it to nearest even integer.
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*/
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uint16_t divisor = rint(PIT_CLOCK_FREQUENCY / ticks_rate);
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/* Setup Control register flags in a didactic way. */
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uint8_t flags = 0x30; /* Set bits 7:6 to select Counter0 and 5:4 to select "write 7:0 bits first". */
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flags |= 0x6; /* Set bits 3:1 to Mode 3 and bit 0 to BCD off. */
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outb(PIT_CONTROL_PORT, flags);
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outb(PIT_COUNTER0_PORT, divisor & 0xFF); /* Write least significant bytes first. */
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outb(PIT_COUNTER0_PORT, (divisor >> 8) & 0xFF);
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/* FIXME: Unmask IRQ0 from Master PIC. Add a pic_set_mask() or similar and call it here. */
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outb(0x21, 0xfa);
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}
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