/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * 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
 *
 * 1 tab == 4 spaces!
 */

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ST STR71x ARM7
 * port.
 *----------------------------------------------------------*/

/* Library includes. */
#include "wdg.h"
#include "eic.h"

/* 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 handle critical sections. */
#define portNO_CRITICAL_NESTING 		( ( uint32_t ) 0 )

#define portMICROS_PER_SECOND 1000000

/*-----------------------------------------------------------*/

/* Setup the watchdog 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;

/* Tick interrupt routines for cooperative and preemptive operation
respectively.  The preemptive version is not defined as __irq as it is called
from an asm wrapper function. */
__arm __irq void vPortNonPreemptiveTick( void );
void vPortPreemptiveTick( 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.
 */
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.  */
}
/*-----------------------------------------------------------*/

/* The cooperative scheduler requires a normal IRQ service routine to
simply increment the system tick. */
__arm __irq void vPortNonPreemptiveTick( void )
{
	/* 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 interrupt in the watchdog and EIC. */
	WDG->SR = 0x0000;
	portCLEAR_EIC();		
}
/*-----------------------------------------------------------*/

/* This function is called from an asm wrapper, so does not require the __irq
keyword. */
void vPortPreemptiveTick( void )
{
	/* Increment the tick counter. */
	if( xTaskIncrementTick() != pdFALSE )
	{
		/* Select a new task to execute. */
		vTaskSwitchContext();
	}

	/* Clear the interrupt in the watchdog and EIC. */
	WDG->SR = 0x0000;
	portCLEAR_EIC();			
}
/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )
{
	/* Set the watchdog up to generate a periodic tick. */
	WDG_ECITConfig( DISABLE );
	WDG_CntOnOffConfig( DISABLE );
	WDG_PeriodValueConfig( portMICROS_PER_SECOND / configTICK_RATE_HZ );

	/* Setup the tick interrupt in the EIC. */
	EIC_IRQChannelPriorityConfig( WDG_IRQChannel, 1 );
	EIC_IRQChannelConfig( WDG_IRQChannel, ENABLE );
	EIC_IRQConfig( ENABLE );
	WDG_ECITConfig( ENABLE );

	/* Start the timer - interrupts are actually disabled at this point so
	it is safe to do this here. */
	WDG_CntOnOffConfig( ENABLE );
}
/*-----------------------------------------------------------*/

__arm __interwork 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++;
}
/*-----------------------------------------------------------*/

__arm __interwork 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();
		}
	}
}
/*-----------------------------------------------------------*/