| /* |
| * FreeRTOS Kernel <DEVELOPMENT BRANCH> |
| * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
| * |
| * SPDX-License-Identifier: MIT |
| * |
| * 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. |
| * |
| * https://www.FreeRTOS.org |
| * https://github.com/FreeRTOS |
| * |
| */ |
| |
| /* |
| Changes from V1.00: |
| |
| + Call to taskYIELD() from within tick ISR has been replaced by the more |
| efficient portSWITCH_CONTEXT(). |
| + ISR function definitions renamed to include the prv prefix. |
| |
| Changes from V1.2.0: |
| |
| + prvPortResetPIC() is now called last thing before the end of the |
| preemptive tick routine. |
| |
| Changes from V2.6.1 |
| |
| + Replaced the sUsingPreemption variable with the configUSE_PREEMPTION |
| macro to be consistent with the later ports. |
| |
| Changes from V4.0.1 |
| |
| + Add function prvSetTickFrequencyDefault() to set the DOS tick back to |
| its proper value when the scheduler exits. |
| */ |
| |
| #include <stdlib.h> |
| #include <stdio.h> |
| #include <i86.h> |
| #include <dos.h> |
| #include <setjmp.h> |
| |
| #include "FreeRTOS.h" |
| #include "task.h" |
| #include "portasm.h" |
| |
| /*----------------------------------------------------------- |
| * Implementation of functions defined in portable.h for the industrial |
| * PC port. |
| *----------------------------------------------------------*/ |
| |
| /*lint -e950 Non ANSI reserved words okay in this file only. */ |
| |
| #define portTIMER_INT_NUMBER 0x08 |
| |
| /* Setup hardware for required tick interrupt rate. */ |
| static void prvSetTickFrequency( uint32_t ulTickRateHz ); |
| |
| /* Restore hardware to as it was prior to starting the scheduler. */ |
| static void prvExitFunction( void ); |
| |
| /* Either chain to the DOS tick (which itself clears the PIC) or clear the PIC |
| directly. We chain to the DOS tick as close as possible to the standard DOS |
| tick rate. */ |
| static void prvPortResetPIC( void ); |
| |
| /* The tick ISR used depends on whether the preemptive or cooperative scheduler |
| is being used. */ |
| #if configUSE_PREEMPTION == 1 |
| /* Tick service routine used by the scheduler when preemptive scheduling is |
| being used. */ |
| static void __interrupt __far prvPreemptiveTick( void ); |
| #else |
| /* Tick service routine used by the scheduler when cooperative scheduling is |
| being used. */ |
| static void __interrupt __far prvNonPreemptiveTick( void ); |
| #endif |
| /* Trap routine used by taskYIELD() to manually cause a context switch. */ |
| static void __interrupt __far prvYieldProcessor( void ); |
| |
| /* Set the tick frequency back so the floppy drive works correctly when the |
| scheduler exits. */ |
| static void prvSetTickFrequencyDefault( void ); |
| |
| /*lint -e956 File scopes necessary here. */ |
| |
| /* Used to signal when to chain to the DOS tick, and when to just clear the PIC ourselves. */ |
| static int16_t sDOSTickCounter; |
| |
| /* Set true when the vectors are set so the scheduler will service the tick. */ |
| static int16_t sSchedulerRunning = pdFALSE; |
| |
| /* 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(). */ |
| static void ( __interrupt __far *pxOldSwitchISR )(); |
| |
| /* 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(). */ |
| static void ( __interrupt __far *pxOldSwitchISRPlus1 )(); |
| |
| /* Used to restore the original DOS context when the scheduler is ended. */ |
| static jmp_buf xJumpBuf; |
| |
| /*lint +e956 */ |
| |
| /*-----------------------------------------------------------*/ |
| BaseType_t xPortStartScheduler( void ) |
| { |
| pxISR pxOriginalTickISR; |
| |
| /* This is called with interrupts already disabled. */ |
| |
| /* Remember what was on the interrupts we are going to use |
| so we can put them back later if required. */ |
| pxOldSwitchISR = _dos_getvect( portSWITCH_INT_NUMBER ); |
| pxOriginalTickISR = _dos_getvect( portTIMER_INT_NUMBER ); |
| pxOldSwitchISRPlus1 = _dos_getvect( portSWITCH_INT_NUMBER + 1 ); |
| |
| prvSetTickFrequency( configTICK_RATE_HZ ); |
| |
| /* Put our manual switch (yield) function on a known |
| vector. */ |
| _dos_setvect( portSWITCH_INT_NUMBER, prvYieldProcessor ); |
| |
| /* Put the old tick on a different interrupt number so we can |
| call it when we want. */ |
| _dos_setvect( portSWITCH_INT_NUMBER + 1, pxOriginalTickISR ); |
| |
| #if configUSE_PREEMPTION == 1 |
| { |
| /* Put our tick switch function on the timer interrupt. */ |
| _dos_setvect( portTIMER_INT_NUMBER, prvPreemptiveTick ); |
| } |
| #else |
| { |
| /* We want the timer interrupt to just increment the tick count. */ |
| _dos_setvect( portTIMER_INT_NUMBER, prvNonPreemptiveTick ); |
| } |
| #endif |
| |
| /* Setup a counter that is used to call the DOS interrupt as close |
| to it's original frequency as can be achieved given our chosen tick |
| frequency. */ |
| sDOSTickCounter = portTICKS_PER_DOS_TICK; |
| |
| /* Clean up function if we want to return to DOS. */ |
| if( setjmp( xJumpBuf ) != 0 ) |
| { |
| prvExitFunction(); |
| sSchedulerRunning = pdFALSE; |
| } |
| else |
| { |
| sSchedulerRunning = pdTRUE; |
| |
| /* Kick off the scheduler by setting up the context of the first task. */ |
| portFIRST_CONTEXT(); |
| } |
| |
| return sSchedulerRunning; |
| } |
| /*-----------------------------------------------------------*/ |
| |
| /* The tick ISR used depends on whether the preemptive or cooperative scheduler |
| is being used. */ |
| #if configUSE_PREEMPTION == 1 |
| /* Tick service routine used by the scheduler when preemptive scheduling is |
| being used. */ |
| static void __interrupt __far prvPreemptiveTick( void ) |
| { |
| /* Get the scheduler to update the task states following the tick. */ |
| if( xTaskIncrementTick() != pdFALSE ) |
| { |
| /* Switch in the context of the next task to be run. */ |
| portSWITCH_CONTEXT(); |
| } |
| |
| /* Reset the PIC ready for the next time. */ |
| prvPortResetPIC(); |
| } |
| #else |
| static void __interrupt __far prvNonPreemptiveTick( void ) |
| { |
| /* Same as preemptive tick, but the cooperative scheduler is being used |
| so we don't have to switch in the context of the next task. */ |
| xTaskIncrementTick(); |
| prvPortResetPIC(); |
| } |
| #endif |
| /*-----------------------------------------------------------*/ |
| |
| |
| static void __interrupt __far prvYieldProcessor( void ) |
| { |
| /* Switch in the context of the next task to be run. */ |
| portSWITCH_CONTEXT(); |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvPortResetPIC( void ) |
| { |
| /* We are going to call the DOS tick interrupt at as close a |
| frequency to the normal DOS tick as possible. */ |
| |
| /* WE SHOULD NOT DO THIS IF YIELD WAS CALLED. */ |
| --sDOSTickCounter; |
| if( sDOSTickCounter <= 0 ) |
| { |
| sDOSTickCounter = ( int16_t ) portTICKS_PER_DOS_TICK; |
| __asm{ int portSWITCH_INT_NUMBER + 1 }; |
| } |
| else |
| { |
| /* Reset the PIC as the DOS tick is not being called to |
| do it. */ |
| __asm |
| { |
| mov al, 20H |
| out 20H, al |
| }; |
| } |
| } |
| /*-----------------------------------------------------------*/ |
| |
| void vPortEndScheduler( void ) |
| { |
| /* Jump back to the processor state prior to starting the |
| scheduler. This means we are not going to be using a |
| task stack frame so the task can be deleted. */ |
| longjmp( xJumpBuf, 1 ); |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvExitFunction( void ) |
| { |
| void ( __interrupt __far *pxOriginalTickISR )(); |
| |
| /* Interrupts should be disabled here anyway - but no |
| harm in making sure. */ |
| portDISABLE_INTERRUPTS(); |
| if( sSchedulerRunning == pdTRUE ) |
| { |
| /* Set the DOS tick back onto the timer ticker. */ |
| pxOriginalTickISR = _dos_getvect( portSWITCH_INT_NUMBER + 1 ); |
| _dos_setvect( portTIMER_INT_NUMBER, pxOriginalTickISR ); |
| prvSetTickFrequencyDefault(); |
| |
| /* Put back the switch interrupt routines that was in place |
| before the scheduler started. */ |
| _dos_setvect( portSWITCH_INT_NUMBER, pxOldSwitchISR ); |
| _dos_setvect( portSWITCH_INT_NUMBER + 1, pxOldSwitchISRPlus1 ); |
| } |
| /* The tick timer is back how DOS wants it. We can re-enable |
| interrupts without the scheduler being called. */ |
| portENABLE_INTERRUPTS(); |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvSetTickFrequency( uint32_t ulTickRateHz ) |
| { |
| const uint16_t usPIT_MODE = ( uint16_t ) 0x43; |
| const uint16_t usPIT0 = ( uint16_t ) 0x40; |
| const uint32_t ulPIT_CONST = ( uint32_t ) 1193180; |
| const uint16_t us8254_CTR0_MODE3 = ( uint16_t ) 0x36; |
| uint32_t ulOutput; |
| |
| /* Setup the 8245 to tick at the wanted frequency. */ |
| portOUTPUT_BYTE( usPIT_MODE, us8254_CTR0_MODE3 ); |
| ulOutput = ulPIT_CONST / ulTickRateHz; |
| |
| portOUTPUT_BYTE( usPIT0, ( uint16_t )( ulOutput & ( uint32_t ) 0xff ) ); |
| ulOutput >>= 8; |
| portOUTPUT_BYTE( usPIT0, ( uint16_t ) ( ulOutput & ( uint32_t ) 0xff ) ); |
| } |
| /*-----------------------------------------------------------*/ |
| |
| static void prvSetTickFrequencyDefault( void ) |
| { |
| const uint16_t usPIT_MODE = ( uint16_t ) 0x43; |
| const uint16_t usPIT0 = ( uint16_t ) 0x40; |
| const uint16_t us8254_CTR0_MODE3 = ( uint16_t ) 0x36; |
| |
| portOUTPUT_BYTE( usPIT_MODE, us8254_CTR0_MODE3 ); |
| portOUTPUT_BYTE( usPIT0,0 ); |
| portOUTPUT_BYTE( usPIT0,0 ); |
| } |
| |
| |
| /*lint +e950 */ |