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First version under SVN is V4.0.1
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Richard Barry
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918 changed files with 269038 additions and 0 deletions
294
Source/portable/oWatcom/16BitDOS/PC/port.c
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294
Source/portable/oWatcom/16BitDOS/PC/port.c
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/*
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FreeRTOS V4.0.1 - Copyright (C) 2003-2006 Richard Barry.
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This file is part of the FreeRTOS distribution.
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FreeRTOS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FreeRTOS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FreeRTOS; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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A special exception to the GPL can be applied should you wish to distribute
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a combined work that includes FreeRTOS, without being obliged to provide
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the source code for any proprietary components. See the licensing section
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of http://www.FreeRTOS.org for full details of how and when the exception
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can be applied.
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***************************************************************************
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See http://www.FreeRTOS.org for documentation, latest information, license
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and contact details. Please ensure to read the configuration and relevant
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port sections of the online documentation.
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***************************************************************************
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*/
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/*
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Changes from V1.00:
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+ Call to taskYIELD() from within tick ISR has been replaced by the more
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efficient portSWITCH_CONTEXT().
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+ ISR function definitions renamed to include the prv prefix.
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Changes from V1.2.0:
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+ prvPortResetPIC() is now called last thing before the end of the
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preemptive tick routine.
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Changes from V2.6.1
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+ Replaced the sUsingPreemption variable with the configUSE_PREEMPTION
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macro to be consistent with the later ports.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <i86.h>
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#include <dos.h>
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#include <setjmp.h>
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#include "FreeRTOS.h"
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#include "task.h"
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#include "portasm.h"
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/*-----------------------------------------------------------
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* Implementation of functions defined in portable.h for the industrial
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* PC port.
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*----------------------------------------------------------*/
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/*lint -e950 Non ANSI reserved words okay in this file only. */
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#define portTIMER_INT_NUMBER 0x08
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/* Setup hardware for required tick interrupt rate. */
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static void prvSetTickFrequency( unsigned portLONG ulTickRateHz );
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/* Restore hardware to as it was prior to starting the scheduler. */
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static void prvExitFunction( void );
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/* Either chain to the DOS tick (which itself clears the PIC) or clear the PIC
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directly. We chain to the DOS tick as close as possible to the standard DOS
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tick rate. */
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static void prvPortResetPIC( void );
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/* The tick ISR used depends on whether the preemptive or cooperative scheduler
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is being used. */
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#if configUSE_PREEMPTION == 1
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/* Tick service routine used by the scheduler when preemptive scheduling is
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being used. */
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static void __interrupt __far prvPreemptiveTick( void );
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#else
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/* Tick service routine used by the scheduler when cooperative scheduling is
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being used. */
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static void __interrupt __far prvNonPreemptiveTick( void );
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#endif
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/* Trap routine used by taskYIELD() to manually cause a context switch. */
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static void __interrupt __far prvYieldProcessor( void );
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/*lint -e956 File scopes necessary here. */
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/* Used to signal when to chain to the DOS tick, and when to just clear the PIC ourselves. */
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static portSHORT sDOSTickCounter;
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/* Set true when the vectors are set so the scheduler will service the tick. */
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static portSHORT sSchedulerRunning = pdFALSE;
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/* Points to the original routine installed on the vector we use for manual context switches. This is then used to restore the original routine during prvExitFunction(). */
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static void ( __interrupt __far *pxOldSwitchISR )();
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/* Points to the original routine installed on the vector we use to chain to the DOS tick. This is then used to restore the original routine during prvExitFunction(). */
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static void ( __interrupt __far *pxOldSwitchISRPlus1 )();
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/* Used to restore the original DOS context when the scheduler is ended. */
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static jmp_buf xJumpBuf;
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/*lint +e956 */
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/*-----------------------------------------------------------*/
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portBASE_TYPE xPortStartScheduler( void )
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{
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pxISR pxOriginalTickISR;
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/* This is called with interrupts already disabled. */
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/* Remember what was on the interrupts we are going to use
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so we can put them back later if required. */
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pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER );
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pxOriginalTickISR = _dos_getvect( portTIMER_INT_NUMBER );
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pxOldSwitchISRPlus1 = _dos_getvect( portSWITCH_INT_NUMBER + 1 );
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prvSetTickFrequency( configTICK_RATE_HZ );
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/* Put our manual switch (yield) function on a known
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vector. */
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_dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );
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/* Put the old tick on a different interrupt number so we can
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call it when we want. */
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_dos_setvect( portSWITCH_INT_NUMBER + 1, pxOriginalTickISR );
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#if configUSE_PREEMPTION == 1
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{
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/* Put our tick switch function on the timer interrupt. */
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_dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick );
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}
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#else
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{
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/* We want the timer interrupt to just increment the tick count. */
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_dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick );
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}
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#endif
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/* Setup a counter that is used to call the DOS interrupt as close
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to it's original frequency as can be achieved given our chosen tick
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frequency. */
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sDOSTickCounter = portTICKS_PER_DOS_TICK;
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/* Clean up function if we want to return to DOS. */
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if( setjmp( xJumpBuf ) != 0 )
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{
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prvExitFunction();
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sSchedulerRunning = pdFALSE;
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}
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else
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{
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sSchedulerRunning = pdTRUE;
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/* Kick off the scheduler by setting up the context of the first task. */
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portFIRST_CONTEXT();
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}
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return sSchedulerRunning;
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}
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/*-----------------------------------------------------------*/
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/* The tick ISR used depends on whether the preemptive or cooperative scheduler
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is being used. */
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#if configUSE_PREEMPTION == 1
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/* Tick service routine used by the scheduler when preemptive scheduling is
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being used. */
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static void __interrupt __far prvPreemptiveTick( void )
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{
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/* Get the scheduler to update the task states following the tick. */
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vTaskIncrementTick();
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/* Switch in the context of the next task to be run. */
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portSWITCH_CONTEXT();
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/* Reset the PIC ready for the next time. */
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prvPortResetPIC();
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}
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#else
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static void __interrupt __far prvNonPreemptiveTick( void )
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{
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/* Same as preemptive tick, but the cooperative scheduler is being used
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so we don't have to switch in the context of the next task. */
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vTaskIncrementTick();
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prvPortResetPIC();
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}
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#endif
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/*-----------------------------------------------------------*/
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static void __interrupt __far prvYieldProcessor( void )
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{
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/* Switch in the context of the next task to be run. */
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portSWITCH_CONTEXT();
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}
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/*-----------------------------------------------------------*/
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static void prvPortResetPIC( void )
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{
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/* We are going to call the DOS tick interrupt at as close a
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frequency to the normal DOS tick as possible. */
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/* WE SHOULD NOT DO THIS IF YIELD WAS CALLED. */
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--sDOSTickCounter;
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if( sDOSTickCounter <= 0 )
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{
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sDOSTickCounter = ( portSHORT ) portTICKS_PER_DOS_TICK;
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__asm{ int portSWITCH_INT_NUMBER + 1 };
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}
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else
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{
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/* Reset the PIC as the DOS tick is not being called to
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do it. */
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__asm
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{
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mov al, 20H
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out 20H, al
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};
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}
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}
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/*-----------------------------------------------------------*/
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void vPortEndScheduler( void )
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{
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/* Jump back to the processor state prior to starting the
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scheduler. This means we are not going to be using a
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task stack frame so the task can be deleted. */
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longjmp( xJumpBuf, 1 );
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}
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/*-----------------------------------------------------------*/
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static void prvExitFunction( void )
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{
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void ( __interrupt __far *pxOriginalTickISR )();
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/* Interrupts should be disabled here anyway - but no
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harm in making sure. */
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portDISABLE_INTERRUPTS();
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if( sSchedulerRunning == pdTRUE )
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{
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/* Set the DOS tick back onto the timer ticker. */
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pxOriginalTickISR = _dos_getvect( portSWITCH_INT_NUMBER + 1 );
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_dos_setvect( portTIMER_INT_NUMBER, pxOriginalTickISR );
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/* This won't set the frequency quite the same as it was,
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but using an integer value removes the need for any floating
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point in the scheduler code. */
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prvSetTickFrequency( ( unsigned portLONG ) portDOS_TICK_RATE );
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/* Put back the switch interrupt routines that was in place
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before the scheduler started. */
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_dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR );
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_dos_setvect( portSWITCH_INT_NUMBER + 1, pxOldSwitchISRPlus1 );
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}
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/* The tick timer is back how DOS wants it. We can re-enable
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interrupts without the scheduler being called. */
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portENABLE_INTERRUPTS();
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/* This will free up all the memory used by the scheduler.
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exiting back to dos with INT21 AH=4CH will do this anyway so
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it is not necessary to call this. */
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vTaskCleanUpResources();
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}
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/*-----------------------------------------------------------*/
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static void prvSetTickFrequency( unsigned portLONG ulTickRateHz )
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{
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const unsigned portSHORT usPIT_MODE = ( unsigned portSHORT ) 0x43;
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const unsigned portSHORT usPIT0 = ( unsigned portSHORT ) 0x40;
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const unsigned portLONG ulPIT_CONST = ( unsigned portLONG ) 1193180;
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const unsigned portSHORT us8254_CTR0_MODE3 = ( unsigned portSHORT ) 0x36;
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unsigned portLONG ulOutput;
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/* Setup the 8245 to tick at the wanted frequency. */
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portOUTPUT_BYTE( usPIT_MODE, us8254_CTR0_MODE3 );
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ulOutput = ulPIT_CONST / ulTickRateHz;
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portOUTPUT_BYTE( usPIT0, ( unsigned portSHORT )( ulOutput & ( unsigned portLONG ) 0xff ) );
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ulOutput >>= 8;
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portOUTPUT_BYTE( usPIT0, ( unsigned portSHORT ) ( ulOutput & ( unsigned portLONG ) 0xff ) );
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}
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/*lint +e950 */
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