/* FreeRTOS.org V5.1.1 - Copyright (C) 2003-2008 Richard Barry. This file is part of the FreeRTOS.org distribution. FreeRTOS.org is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. FreeRTOS.org is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with FreeRTOS.org; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA A special exception to the GPL can be applied should you wish to distribute a combined work that includes FreeRTOS.org, without being obliged to provide the source code for any proprietary components. See the licensing section of http://www.FreeRTOS.org for full details of how and when the exception can be applied. *************************************************************************** *************************************************************************** * * * SAVE TIME AND MONEY! We can port FreeRTOS.org to your own hardware, * * and even write all or part of your application on your behalf. * * See http://www.OpenRTOS.com for details of the services we provide to * * expedite your project. * * * *************************************************************************** *************************************************************************** Please ensure to read the configuration and relevant port sections of the online documentation. http://www.FreeRTOS.org - Documentation, latest information, license and contact details. http://www.SafeRTOS.com - A version that is certified for use in safety critical systems. http://www.OpenRTOS.com - Commercial support, development, porting, licensing and training services. */ /*----------------------------------------------------------- * Implementation of functions defined in portable.h for the ARM7 port. * * Components that can be compiled to either ARM or THUMB mode are * contained in this file. The ISR routines, which can only be compiled * to ARM mode are contained in portISR.c. *----------------------------------------------------------*/ /* Changes from V2.5.2 + ulCriticalNesting is now saved as part of the task context, as is therefore added to the initial task stack during pxPortInitialiseStack. Changes from V3.2.2 + Bug fix - The prescale value for the timer setup is now written to T0_PR instead of T0_PC. This bug would have had no effect unless a prescale value was actually used. */ /* Standard includes. */ #include /* Scheduler includes. */ #include "FreeRTOS.h" #include "task.h" /* Constants required to setup the task context. */ #define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */ #define portTHUMB_MODE_BIT ( ( portSTACK_TYPE ) 0x20 ) #define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 ) #define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 ) /* Constants required to setup the tick ISR. */ #define portENABLE_TIMER ( ( unsigned portCHAR ) 0x01 ) #define portPRESCALE_VALUE 0x00 #define portINTERRUPT_ON_MATCH ( ( unsigned portLONG ) 0x01 ) #define portRESET_COUNT_ON_MATCH ( ( unsigned portLONG ) 0x02 ) /* Constants required to setup the VIC for the tick ISR. */ #define portTIMER_VIC_CHANNEL ( ( unsigned portLONG ) 0x0004 ) #define portTIMER_VIC_CHANNEL_BIT ( ( unsigned portLONG ) 0x0010 ) #define portTIMER_VIC_ENABLE ( ( unsigned portLONG ) 0x0020 ) /*-----------------------------------------------------------*/ /* Setup the timer to generate the tick interrupts. */ static void prvSetupTimerInterrupt( void ); /* * The scheduler can only be started from ARM mode, so * vPortISRStartFirstSTask() is defined in portISR.c. */ extern void vPortISRStartFirstTask( void ); /*-----------------------------------------------------------*/ /* * Initialise the stack of a task to look exactly as if a call to * portSAVE_CONTEXT had been called. * * See header file for description. */ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters ) { portSTACK_TYPE *pxOriginalTOS; pxOriginalTOS = pxTopOfStack; /* Setup the initial stack of the task. The stack is set exactly as expected by the portRESTORE_CONTEXT() macro. */ /* First on the stack is the return address - which in this case is the start of the task. The offset is added to make the return address appear as it would within an IRQ ISR. */ *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE; pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaaaaaa; /* R14 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212; /* R12 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111; /* R11 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010; /* R10 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909; /* R9 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808; /* R8 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707; /* R7 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606; /* R6 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505; /* R5 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404; /* R4 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303; /* R3 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202; /* R2 */ pxTopOfStack--; *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101; /* R1 */ pxTopOfStack--; /* When the task starts is will expect to find the function parameter in R0. */ *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */ pxTopOfStack--; /* The last thing onto the stack is the status register, which is set for system mode, with interrupts enabled. */ *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR; #ifdef THUMB_INTERWORK { /* We want the task to start in thumb mode. */ *pxTopOfStack |= portTHUMB_MODE_BIT; } #endif pxTopOfStack--; /* Some optimisation levels use the stack differently to others. This means the interrupt flags cannot always be stored on the stack and will instead be stored in a variable, which is then saved as part of the tasks context. */ *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING; return pxTopOfStack; } /*-----------------------------------------------------------*/ portBASE_TYPE xPortStartScheduler( void ) { /* Start the timer that generates the tick ISR. Interrupts are disabled here already. */ prvSetupTimerInterrupt(); /* Start the first task. */ vPortISRStartFirstTask(); /* Should not get here! */ return 0; } /*-----------------------------------------------------------*/ void vPortEndScheduler( void ) { /* It is unlikely that the ARM port will require this function as there is nothing to return to. */ } /*-----------------------------------------------------------*/ /* * Setup the timer 0 to generate the tick interrupts at the required frequency. */ static void prvSetupTimerInterrupt( void ) { unsigned portLONG ulCompareMatch; extern void ( vTickISR )( void ); /* A 1ms tick does not require the use of the timer prescale. This is defaulted to zero but can be used if necessary. */ T0_PR = portPRESCALE_VALUE; /* Calculate the match value required for our wanted tick rate. */ ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ; /* Protect against divide by zero. Using an if() statement still results in a warning - hence the #if. */ #if portPRESCALE_VALUE != 0 { ulCompareMatch /= ( portPRESCALE_VALUE + 1 ); } #endif T0_MR0 = ulCompareMatch; /* Generate tick with timer 0 compare match. */ T0_MCR = portRESET_COUNT_ON_MATCH | portINTERRUPT_ON_MATCH; /* Setup the VIC for the timer. */ VICIntSelect &= ~( portTIMER_VIC_CHANNEL_BIT ); VICIntEnable |= portTIMER_VIC_CHANNEL_BIT; /* The ISR installed depends on whether the preemptive or cooperative scheduler is being used. */ VICVectAddr0 = ( portLONG ) vTickISR; VICVectCntl0 = portTIMER_VIC_CHANNEL | portTIMER_VIC_ENABLE; /* Start the timer - interrupts are disabled when this function is called so it is okay to do this here. */ T0_TCR = portENABLE_TIMER; } /*-----------------------------------------------------------*/