galileo: Add PIT driver
This patch adds a driver for the 8254 Programmable Interrupt Timer (PIT). The driver introduced by this patch programs the PIT to generate interrupt periodically. The interrupt frequency can be configured by the user. On each PIT interrupt, a callback configured by the user is called. As expected, that callback is executed in interrupt context so the user should be aware of what it is not supposed to do (e.g. to call blocking functions). Issues marked as FIXME are all related to missing APIs on the PIC driver so they will be addressed by a future commit.
This commit is contained in:
Jesus Sanchez-Palencia
parent
7c871871de
commit
d70f67cd60
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CONTIKI_CPU_DIRS = . drivers
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CONTIKI_SOURCEFILES += mtarch.c gdt.c helpers.S idt.c cpu.c rtc.c
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CONTIKI_SOURCEFILES += mtarch.c gdt.c helpers.S idt.c cpu.c rtc.c pit.c
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### Compiler definitions
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CC = gcc
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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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@ -0,0 +1,45 @@
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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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#ifndef PIT_H
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#define PIT_H
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#include <stdint.h>
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typedef void (*pit_int_callback)(void);
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/**
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* Initializes the 8254 Programmable Interrupt Timer chip (Counter 0 only).
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* The PIT Interrupt callback is implemented by the driver's users. It is
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* called from interrupt context, so it has to return as soon as possible.
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*/
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void pit_init(uint32_t ticks_rate, pit_int_callback c);
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#endif /* PIT_H */
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