/*
    FreeRTOS V7.3.0 - Copyright (C) 2012 Real Time Engineers Ltd.

    FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME.  PLEASE VISIT 
    http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS tutorial books are available in pdf and paperback.        *
     *    Complete, revised, and edited pdf reference manuals are also       *
     *    available.                                                         *
     *                                                                       *
     *    Purchasing FreeRTOS documentation will not only help you, by       *
     *    ensuring you get running as quickly as possible and with an        *
     *    in-depth knowledge of how to use FreeRTOS, it will also help       *
     *    the FreeRTOS project to continue with its mission of providing     *
     *    professional grade, cross platform, de facto standard solutions    *
     *    for microcontrollers - completely free of charge!                  *
     *                                                                       *
     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
     *                                                                       *
     *    Thank you for using FreeRTOS, and thank you for your support!      *
     *                                                                       *
    ***************************************************************************


    This file is part of the FreeRTOS distribution.

    FreeRTOS 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 modification to the GPL is included to allow you to
    distribute a combined work that includes FreeRTOS without being obliged to
    provide the source code for proprietary components outside of the FreeRTOS
    kernel.  FreeRTOS 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 and the FreeRTOS license exception along with FreeRTOS; if not it
    can be viewed here: http://www.freertos.org/a00114.html and also obtained
    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.

    1 tab == 4 spaces!
    
    ***************************************************************************
     *                                                                       *
     *    Having a problem?  Start by reading the FAQ "My application does   *
     *    not run, what could be wrong?"                                     *
     *                                                                       *
     *    http://www.FreeRTOS.org/FAQHelp.html                               *
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    ***************************************************************************

    
    http://www.FreeRTOS.org - Documentation, training, latest versions, license 
    and contact details.  
    
    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
    including FreeRTOS+Trace - an indispensable productivity tool.

    Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell 
    the code with commercial support, indemnification, and middleware, under 
    the OpenRTOS brand: http://www.OpenRTOS.com.  High Integrity Systems also
    provide a safety engineered and independently SIL3 certified version under 
    the SafeRTOS brand: http://www.SafeRTOS.com.
*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the NIOS2 port.
 *----------------------------------------------------------*/

/* Standard Includes. */
#include <string.h>
#include <errno.h>

/* Altera includes. */
#include "sys/alt_irq.h"
#include "altera_avalon_timer_regs.h"
#include "priv/alt_irq_table.h"

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Interrupts are enabled. */
#define portINITIAL_ESTATUS     ( portSTACK_TYPE ) 0x01 

/*-----------------------------------------------------------*/

/* 
 * Setup the timer to generate the tick interrupts.
 */
static void prvSetupTimerInterrupt( void );

/*
 * Call back for the alarm function.
 */
void vPortSysTickHandler( void * context, alt_u32 id );

/*-----------------------------------------------------------*/

static void prvReadGp( unsigned long *ulValue )
{
	asm( "stw gp, (%0)" :: "r"(ulValue) );
}
/*-----------------------------------------------------------*/

/* 
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{    
portSTACK_TYPE *pxFramePointer = pxTopOfStack - 1;
portSTACK_TYPE xGlobalPointer;

    prvReadGp( &xGlobalPointer ); 

    /* End of stack marker. */
    *pxTopOfStack = 0xdeadbeef;
    pxTopOfStack--;
    
    *pxTopOfStack = ( portSTACK_TYPE ) pxFramePointer; 
    pxTopOfStack--;
    
    *pxTopOfStack = xGlobalPointer; 
    
    /* Space for R23 to R16. */
    pxTopOfStack -= 9;

    *pxTopOfStack = ( portSTACK_TYPE ) pxCode; 
    pxTopOfStack--;

    *pxTopOfStack = portINITIAL_ESTATUS; 

    /* Space for R15 to R5. */    
    pxTopOfStack -= 12;
    
    *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; 

    /* Space for R3 to R1, muldiv and RA. */
    pxTopOfStack -= 5;
    
    return pxTopOfStack;
}
/*-----------------------------------------------------------*/

/* 
 * See header file for description. 
 */
portBASE_TYPE xPortStartScheduler( void )
{
	/* Start the timer that generates the tick ISR.  Interrupts are disabled
	here already. */
	prvSetupTimerInterrupt();
	
	/* Start the first task. */
    asm volatile (  " movia r2, restore_sp_from_pxCurrentTCB        \n"
                    " jmp r2                                          " );

	/* Should not get here! */
	return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* It is unlikely that the NIOS2 port will require this function as there
	is nothing to return to.  */
}
/*-----------------------------------------------------------*/

/*
 * Setup the systick timer to generate the tick interrupts at the required
 * frequency.
 */
void prvSetupTimerInterrupt( void )
{
	/* Try to register the interrupt handler. */
	if ( -EINVAL == alt_irq_register( SYS_CLK_IRQ, 0x0, vPortSysTickHandler ) )
	{ 
		/* Failed to install the Interrupt Handler. */
		asm( "break" );
	}
	else
	{
		/* Configure SysTick to interrupt at the requested rate. */
		IOWR_ALTERA_AVALON_TIMER_CONTROL( SYS_CLK_BASE, ALTERA_AVALON_TIMER_CONTROL_STOP_MSK );
		IOWR_ALTERA_AVALON_TIMER_PERIODL( SYS_CLK_BASE, ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) & 0xFFFF );
		IOWR_ALTERA_AVALON_TIMER_PERIODH( SYS_CLK_BASE, ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) >> 16 );
		IOWR_ALTERA_AVALON_TIMER_CONTROL( SYS_CLK_BASE, ALTERA_AVALON_TIMER_CONTROL_CONT_MSK | ALTERA_AVALON_TIMER_CONTROL_START_MSK | ALTERA_AVALON_TIMER_CONTROL_ITO_MSK );	
	} 

	/* Clear any already pending interrupts generated by the Timer. */
	IOWR_ALTERA_AVALON_TIMER_STATUS( SYS_CLK_BASE, ~ALTERA_AVALON_TIMER_STATUS_TO_MSK );
}
/*-----------------------------------------------------------*/

void vPortSysTickHandler( void * context, alt_u32 id )
{
	/* Increment the Kernel Tick. */
	vTaskIncrementTick();

	/* If using preemption, also force a context switch. */
	#if configUSE_PREEMPTION == 1
        vTaskSwitchContext();
	#endif

	/* Clear the interrupt. */
	IOWR_ALTERA_AVALON_TIMER_STATUS( SYS_CLK_BASE, ~ALTERA_AVALON_TIMER_STATUS_TO_MSK );
}
/*-----------------------------------------------------------*/

/** This function is a re-implementation of the Altera provided function.
 * The function is re-implemented to prevent it from enabling an interrupt
 * when it is registered. Interrupts should only be enabled after the FreeRTOS.org
 * kernel has its scheduler started so that contexts are saved and switched 
 * correctly.
 */
int alt_irq_register( alt_u32 id, void* context, void (*handler)(void*, alt_u32) )
{
	int rc = -EINVAL;  
	alt_irq_context status;

	if (id < ALT_NIRQ)
	{
		/* 
		 * interrupts are disabled while the handler tables are updated to ensure
		 * that an interrupt doesn't occur while the tables are in an inconsistent
		 * state.
		 */
	
		status = alt_irq_disable_all ();
	
		alt_irq[id].handler = handler;
		alt_irq[id].context = context;
	
		rc = (handler) ? alt_irq_enable (id): alt_irq_disable (id);
	
		/* alt_irq_enable_all(status); This line is removed to prevent the interrupt from being immediately enabled. */
	}
    
	return rc; 
}
/*-----------------------------------------------------------*/

