text: /*
   * FreeRTOS Kernel V10.4.4
   * 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
   *
   */
  
  /*-----------------------------------------------------------
   * 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				( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
  #define portTHUMB_MODE_BIT				( ( StackType_t ) 0x20 )
  #define portINSTRUCTION_SIZE			( ( StackType_t ) 4 )
  
  /* Constants required to setup the PIT. */
  #define portPIT_CLOCK_DIVISOR			( ( uint32_t ) 16 )
  #define portPIT_COUNTER_VALUE			( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_PERIOD_MS )
  
  /* Constants required to handle critical sections. */
  #define portNO_CRITICAL_NESTING 		( ( uint32_t ) 0 )
  
  
  #define portINT_LEVEL_SENSITIVE  0
  #define portPIT_ENABLE      	( ( uint16_t ) 0x1 << 24 )
  #define portPIT_INT_ENABLE     	( ( uint16_t ) 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. */
  uint32_t ulCriticalNesting = ( uint32_t ) 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.
   */
  StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
  {
  StackType_t *pxOriginalTOS;
  
  	pxOriginalTOS = pxTopOfStack;
  
  	/* To ensure asserts in tasks.c don't fail, although in this case the assert
  	is not really required. */
  	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 = ( StackType_t ) pxCode + portINSTRUCTION_SIZE;		
  	pxTopOfStack--;
  
  	*pxTopOfStack = ( StackType_t ) 0xaaaaaaaa;	/* R14 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
  	pxTopOfStack--;
  	*pxTopOfStack = ( StackType_t ) 0x12121212;	/* R12 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x11111111;	/* R11 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x10101010;	/* R10 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x09090909;	/* R9 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x08080808;	/* R8 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x07070707;	/* R7 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x06060606;	/* R6 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x05050505;	/* R5 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x04040404;	/* R4 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x03030303;	/* R3 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x02020202;	/* R2 */
  	pxTopOfStack--;	
  	*pxTopOfStack = ( StackType_t ) 0x01010101;	/* R1 */
  	pxTopOfStack--;	
  
  	/* When the task starts is will expect to find the function parameter in
  	R0. */
  	*pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
  	pxTopOfStack--;
  
  	/* The status register is set for system mode, with interrupts enabled. */
  	*pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;
  	
  	if( ( ( uint32_t ) pxCode & 0x01UL ) != 0x00UL )
  	{
  		/* We want the task to start in thumb mode. */
  		*pxTopOfStack |= portTHUMB_MODE_BIT;
  	}	
  	
  	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;	
  }
  /*-----------------------------------------------------------*/
  
  BaseType_t 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 )
  	{
  		uint32_t 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. */
  		xTaskIncrementTick();
  		
  		/* 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();
  		}
  	}
  }
  /*-----------------------------------------------------------*/
  
  
  
  
  
  
  