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First version under SVN is V4.0.1
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Richard Barry
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313
Source/portable/IAR/LPC2000/port.c
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313
Source/portable/IAR/LPC2000/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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* Implementation of functions defined in portable.h for the Philips ARM7 port.
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*----------------------------------------------------------*/
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/*
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Changes from V3.2.2
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+ Bug fix - The prescale value for the timer setup is now written to T0PR
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instead of T0PC. This bug would have had no effect unless a prescale
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value was actually used.
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*/
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/* Standard includes. */
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#include <stdlib.h>
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#include <intrinsic.h>
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/* Scheduler includes. */
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#include "FreeRTOS.h"
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#include "task.h"
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/* Constants required to setup the tick ISR. */
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#define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 )
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#define portPRESCALE_VALUE 0x00
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#define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 )
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#define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 )
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/* Constants required to setup the initial stack. */
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#define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x3f ) /* System mode, THUMB mode, interrupts enabled. */
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#define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
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/* Constants required to setup the PIT. */
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#define portPIT_CLOCK_DIVISOR ( ( unsigned portLONG ) 16 )
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#define portPIT_COUNTER_VALUE ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_RATE_MS )
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/* Constants required to handle interrupts. */
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#define portTIMER_MATCH_ISR_BIT ( ( unsigned portCHAR ) 0x01 )
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#define portCLEAR_VIC_INTERRUPT ( ( unsigned portLONG ) 0 )
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/* Constants required to handle critical sections. */
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#define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
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#define portINT_LEVEL_SENSITIVE 0
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#define portPIT_ENABLE ( ( unsigned portSHORT ) 0x1 << 24 )
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#define portPIT_INT_ENABLE ( ( unsigned portSHORT ) 0x1 << 25 )
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/* Constants required to setup the VIC for the tick ISR. */
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#define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 )
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#define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 )
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#define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 )
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/*-----------------------------------------------------------*/
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/* Setup the PIT to generate the tick interrupts. */
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static void prvSetupTimerInterrupt( void );
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/* ulCriticalNesting will get set to zero when the first task starts. It
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cannot be initialised to 0 as this will cause interrupts to be enabled
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during the kernel initialisation process. */
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unsigned portLONG ulCriticalNesting = ( unsigned portLONG ) 9999;
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/*-----------------------------------------------------------*/
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/*
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* Initialise the stack of a task to look exactly as if a call to
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* portSAVE_CONTEXT had been called.
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*
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* See header file for description.
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*/
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portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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{
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portSTACK_TYPE *pxOriginalTOS;
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pxOriginalTOS = pxTopOfStack;
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/* Setup the initial stack of the task. The stack is set exactly as
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expected by the portRESTORE_CONTEXT() macro. */
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/* First on the stack is the return address - which in this case is the
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start of the task. The offset is added to make the return address appear
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as it would within an IRQ ISR. */
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*pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */
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pxTopOfStack--;
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/* When the task starts is will expect to find the function parameter in
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R0. */
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*pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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pxTopOfStack--;
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/* The status register is set for system mode, with interrupts enabled. */
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*pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
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pxTopOfStack--;
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/* Interrupt flags cannot always be stored on the stack and will
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instead be stored in a variable, which is then saved as part of the
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tasks context. */
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*pxTopOfStack = portNO_CRITICAL_NESTING;
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return pxTopOfStack;
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}
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/*-----------------------------------------------------------*/
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portBASE_TYPE xPortStartScheduler( void )
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{
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extern void vPortStartFirstTask( void );
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/* Start the timer that generates the tick ISR. Interrupts are disabled
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here already. */
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prvSetupTimerInterrupt();
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/* Start the first task. */
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vPortStartFirstTask();
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/* Should not get here! */
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return 0;
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}
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/*-----------------------------------------------------------*/
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void vPortEndScheduler( void )
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{
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/* It is unlikely that the ARM port will require this function as there
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is nothing to return to. */
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}
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/*-----------------------------------------------------------*/
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#if configUSE_PREEMPTION == 0
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/* The cooperative scheduler requires a normal IRQ service routine to
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simply increment the system tick. */
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static __arm __irq void vPortNonPreemptiveTick( void );
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static __arm __irq void vPortNonPreemptiveTick( void )
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{
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/* Increment the tick count - which may wake some tasks but as the
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preemptive scheduler is not being used any woken task is not given
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processor time no matter what its priority. */
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vTaskIncrementTick();
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/* Ready for the next interrupt. */
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T0IR = portTIMER_MATCH_ISR_BIT;
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VICVectAddr = portCLEAR_VIC_INTERRUPT;
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}
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#else
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/* This function is called from an asm wrapper, so does not require the __irq
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keyword. */
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void vPortPreemptiveTick( void );
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void vPortPreemptiveTick( void )
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{
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/* Increment the tick counter. */
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vTaskIncrementTick();
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/* The new tick value might unblock a task. Ensure the highest task that
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is ready to execute is the task that will execute when the tick ISR
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exits. */
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vTaskSwitchContext();
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/* Ready for the next interrupt. */
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T0IR = portTIMER_MATCH_ISR_BIT;
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VICVectAddr = portCLEAR_VIC_INTERRUPT;
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}
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#endif
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/*-----------------------------------------------------------*/
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static void prvSetupTimerInterrupt( void )
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{
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unsigned portLONG ulCompareMatch;
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/* A 1ms tick does not require the use of the timer prescale. This is
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defaulted to zero but can be used if necessary. */
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T0PR = portPRESCALE_VALUE;
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/* Calculate the match value required for our wanted tick rate. */
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ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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/* Protect against divide by zero. Using an if() statement still results
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in a warning - hence the #if. */
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#if portPRESCALE_VALUE != 0
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{
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ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
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}
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#endif
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T0MR0 = ulCompareMatch;
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/* Generate tick with timer 0 compare match. */
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T0MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH;
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/* Setup the VIC for the timer. */
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VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT );
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VICIntEnable |= portTIMER_VIC_CHANNEL_BIT;
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/* The ISR installed depends on whether the preemptive or cooperative
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scheduler is being used. */
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#if configUSE_PREEMPTION == 1
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{
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extern void ( vPortPreemptiveTickEntry )( void );
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VICVectAddr0 = ( unsigned portLONG ) vPortPreemptiveTickEntry;
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}
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#else
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{
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extern void ( vNonPreemptiveTick )( void );
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VICVectAddr0 = ( portLONG ) vPortNonPreemptiveTick;
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}
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#endif
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VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE;
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/* Start the timer - interrupts are disabled when this function is called
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so it is okay to do this here. */
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T0TCR = portENABLE_TIMER;
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}
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/*-----------------------------------------------------------*/
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void vPortEnterCritical( void )
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{
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/* Disable interrupts first! */
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__disable_interrupt();
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/* Now interrupts are disabled ulCriticalNesting can be accessed
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directly. Increment ulCriticalNesting to keep a count of how many times
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portENTER_CRITICAL() has been called. */
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ulCriticalNesting++;
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}
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/*-----------------------------------------------------------*/
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void vPortExitCritical( void )
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{
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if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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{
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/* Decrement the nesting count as we are leaving a critical section. */
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ulCriticalNesting--;
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/* If the nesting level has reached zero then interrupts should be
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re-enabled. */
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if( ulCriticalNesting == portNO_CRITICAL_NESTING )
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{
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__enable_interrupt();
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}
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}
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}
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/*-----------------------------------------------------------*/
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