/*
FreeRTOS.org V5.3.0 - Copyright (C) 2003-2009 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 (version 2) as published
by the Free Software Foundation and modified by the FreeRTOS exception.
**NOTE** The exception to the GPL is included to allow you to distribute a
combined work that includes FreeRTOS.org without being obliged to provide
the source code for any proprietary components. Alternative commercial
license and support terms are also available upon request. See the
licensing section of http://www.FreeRTOS.org for full details.
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.
***************************************************************************
* *
* Get the FreeRTOS eBook! See http://www.FreeRTOS.org/Documentation *
* *
* This is a concise, step by step, 'hands on' guide that describes both *
* general multitasking concepts and FreeRTOS specifics. It presents and *
* explains numerous examples that are written using the FreeRTOS API. *
* Full source code for all the examples is provided in an accompanying *
* .zip file. *
* *
***************************************************************************
1 tab == 4 spaces!
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 Atmel ARM7 port.
*----------------------------------------------------------*/
/* Standard includes. */
#include <stdlib.h>
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
/* Constants required to setup the initial stack. */
#define portINITIAL_SPSR ( ( portSTACK_TYPE ) 0x3f ) /* System mode, THUMB mode, interrupts enabled. */
#define portINSTRUCTION_SIZE ( ( portSTACK_TYPE ) 4 )
/* Constants required to setup the PIT. */
#define portPIT_CLOCK_DIVISOR ( ( unsigned portLONG ) 16 )
#define portPIT_COUNTER_VALUE ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_RATE_MS )
/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING ( ( unsigned portLONG ) 0 )
#define portINT_LEVEL_SENSITIVE 0
#define portPIT_ENABLE ( ( unsigned portSHORT ) 0x1 << 24 )
#define portPIT_INT_ENABLE ( ( unsigned portSHORT ) 0x1 << 25 )
/*-----------------------------------------------------------*/
/* Setup the PIT to generate the tick interrupts. */
static void prvSetupTimerInterrupt( void );
/* ulCriticalNesting will get set to zero when the first task starts. It
cannot be initialised to 0 as this will cause interrupts to be enabled
during the kernel initialisation process. */
unsigned portLONG ulCriticalNesting = ( unsigned portLONG ) 9999;
/*-----------------------------------------------------------*/
/*
* 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 status register is set for system mode, with interrupts enabled. */
*pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;
pxTopOfStack--;
/* 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_NESTING;
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
portBASE_TYPE xPortStartScheduler( void )
{
extern void vPortStartFirstTask( void );
/* Start the timer that generates the tick ISR. Interrupts are disabled
here already. */
prvSetupTimerInterrupt();
/* Start the first task. */
vPortStartFirstTask();
/* 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. */
}
/*-----------------------------------------------------------*/
#if configUSE_PREEMPTION == 0
/* The cooperative scheduler requires a normal IRQ service routine to
simply increment the system tick. */
static __arm __irq void vPortNonPreemptiveTick( void );
static __arm __irq void vPortNonPreemptiveTick( void )
{
unsigned portLONG ulDummy;
/* Increment the tick count - which may wake some tasks but as the
preemptive scheduler is not being used any woken task is not given
processor time no matter what its priority. */
vTaskIncrementTick();
/* Clear the PIT interrupt. */
ulDummy = AT91C_BASE_PITC->PITC_PIVR;
/* End the interrupt in the AIC. */
AT91C_BASE_AIC->AIC_EOICR = ulDummy;
}
#else
/* Currently the IAR port requires the preemptive tick function to be
defined in an asm file. */
#endif
/*-----------------------------------------------------------*/
static void prvSetupTimerInterrupt( void )
{
AT91PS_PITC pxPIT = AT91C_BASE_PITC;
/* Setup the AIC for PIT interrupts. The interrupt routine chosen depends
on whether the preemptive or cooperative scheduler is being used. */
#if configUSE_PREEMPTION == 0
AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortNonPreemptiveTick );
#else
extern void ( vPortPreemptiveTick )( void );
AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortPreemptiveTick );
#endif
/* Configure the PIT period. */
pxPIT->PITC_PIMR = portPIT_ENABLE | portPIT_INT_ENABLE | portPIT_COUNTER_VALUE;
/* Enable the interrupt. Global interrupts are disables at this point so
this is safe. */
AT91F_AIC_EnableIt( AT91C_BASE_AIC, AT91C_ID_SYS );
}
/*-----------------------------------------------------------*/
void vPortEnterCritical( void )
{
/* Disable interrupts first! */
__disable_interrupt();
/* Now interrupts are disabled ulCriticalNesting can be accessed
directly. Increment ulCriticalNesting to keep a count of how many times
portENTER_CRITICAL() has been called. */
ulCriticalNesting++;
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
if( ulCriticalNesting > portNO_CRITICAL_NESTING )
{
/* Decrement the nesting count as we are leaving a critical section. */
ulCriticalNesting--;
/* If the nesting level has reached zero then interrupts should be
re-enabled. */
if( ulCriticalNesting == portNO_CRITICAL_NESTING )
{
__enable_interrupt();
}
}
}
/*-----------------------------------------------------------*/