/*
    FreeRTOS V6.0.0 - Copyright (C) 2009 Real Time Engineers Ltd.

    ***************************************************************************
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    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 exception 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!

    http://www.FreeRTOS.org - Documentation, latest information, license and
    contact details.

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*/


/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the Tern EE 186
 * port.
 *----------------------------------------------------------*/

/* Library includes. */
#include <embedded.h>
#include <ae.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "portasm.h"

/* The timer increments every four clocks, hence the divide by 4. */
#define portTIMER_COMPARE ( unsigned short ) ( ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) / ( unsigned long ) 4 )

/* From the RDC data sheet. */
#define portENABLE_TIMER_AND_INTERRUPT ( unsigned short ) 0xe001

/* Interrupt control. */
#define portEIO_REGISTER 0xff22
#define portCLEAR_INTERRUPT 0x0008

/* Setup the hardware to generate the required tick frequency. */
static void prvSetupTimerInterrupt( void );

/* The ISR used depends on whether the preemptive or cooperative scheduler
is being used. */
#if( configUSE_PREEMPTION == 1 )
	/* Tick service routine used by the scheduler when preemptive scheduling is
	being used. */
	static void __interrupt __far prvPreemptiveTick( void );
#else
	/* Tick service routine used by the scheduler when cooperative scheduling is
	being used. */
	static void __interrupt __far prvNonPreemptiveTick( void );
#endif

/* Trap routine used by taskYIELD() to manually cause a context switch. */
static void __interrupt __far prvYieldProcessor( void );

/* The timer initialisation functions leave interrupts enabled,
which is not what we want.  This ISR is installed temporarily in case
the timer fires before we get a change to disable interrupts again. */
static void __interrupt __far prvDummyISR( void );

/*-----------------------------------------------------------*/
/* See header file for description. */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
portSTACK_TYPE DS_Reg = 0;

	/* Place a few bytes of known values on the bottom of the stack.
	This is just useful for debugging. */

	*pxTopOfStack = 0x1111;
	pxTopOfStack--;
	*pxTopOfStack = 0x2222;
	pxTopOfStack--;
	*pxTopOfStack = 0x3333;
	pxTopOfStack--;

	/* We are going to start the scheduler using a return from interrupt
	instruction to load the program counter, so first there would be the
	function call with parameters preamble. */
	
	*pxTopOfStack = FP_SEG( pvParameters );
	pxTopOfStack--;
	*pxTopOfStack = FP_OFF( pvParameters );
	pxTopOfStack--;
	*pxTopOfStack = FP_SEG( pxCode );
	pxTopOfStack--;
	*pxTopOfStack = FP_OFF( pxCode );
	pxTopOfStack--;

	/* Next the status register and interrupt return address. */
	*pxTopOfStack = portINITIAL_SW;
	pxTopOfStack--;
	*pxTopOfStack = FP_SEG( pxCode );
	pxTopOfStack--;
	*pxTopOfStack = FP_OFF( pxCode );
	pxTopOfStack--;

	/* The remaining registers would be pushed on the stack by our context
	switch function.  These are loaded with values simply to make debugging
	easier. */
	*pxTopOfStack = ( portSTACK_TYPE ) 0xAAAA;	/* AX */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB;	/* BX */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xCCCC;	/* CX */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD;	/* DX */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xEEEE;	/* ES */
	pxTopOfStack--;

	/* We need the true data segment. */
	__asm{	MOV DS_Reg, DS };

	*pxTopOfStack = DS_Reg;						/* DS */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0123;	/* SI */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xDDDD;	/* DI */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0xBBBB;	/* BP */

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
	/* This is called with interrupts already disabled. */

	/* Put our manual switch (yield) function on a known
	vector. */
	setvect( portSWITCH_INT_NUMBER, prvYieldProcessor );

	/* Setup the tick interrupt. */
	prvSetupTimerInterrupt();

	/* Kick off the scheduler by setting up the context of the first task. */
	portFIRST_CONTEXT();

	/* Should not get here! */
	return pdFALSE;
}
/*-----------------------------------------------------------*/

static void __interrupt __far prvDummyISR( void )
{
	/* The timer initialisation functions leave interrupts enabled,
	which is not what we want.  This ISR is installed temporarily in case
	the timer fires before we get a change to disable interrupts again. */
	outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
}
/*-----------------------------------------------------------*/

/* The ISR used depends on whether the preemptive or cooperative scheduler
is being used. */
#if( configUSE_PREEMPTION == 1 )
	static void __interrupt __far prvPreemptiveTick( void )
	{
		/* Get the scheduler to update the task states following the tick. */
		vTaskIncrementTick();

		/* Switch in the context of the next task to be run. */
		portSWITCH_CONTEXT();

		/* Reset interrupt. */
		outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
	}
#else
	static void __interrupt __far prvNonPreemptiveTick( void )
	{
		/* Same as preemptive tick, but the cooperative scheduler is being used
		so we don't have to switch in the context of the next task. */
		vTaskIncrementTick();
		/* Reset interrupt. */
		outport( portEIO_REGISTER, portCLEAR_INTERRUPT );
	}
#endif
/*-----------------------------------------------------------*/

static void __interrupt __far prvYieldProcessor( void )
{
	/* Switch in the context of the next task to be run. */
	portSWITCH_CONTEXT();
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented. */
}
/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )
{
const unsigned short usTimerACompare = portTIMER_COMPARE, usTimerAMode = portENABLE_TIMER_AND_INTERRUPT;
const unsigned short usT2_IRQ = 0x13;

	/* Configure the timer, the dummy handler is used here as the init
	function leaves interrupts enabled. */
	t2_init( usTimerAMode, usTimerACompare, prvDummyISR );

	/* Disable interrupts again before installing the real handlers. */
	portDISABLE_INTERRUPTS();

	#if( configUSE_PREEMPTION == 1 )
		/* Tick service routine used by the scheduler when preemptive scheduling is
		being used. */
		setvect( usT2_IRQ, prvPreemptiveTick );
	#else
		/* Tick service routine used by the scheduler when cooperative scheduling is
		being used. */
		setvect( usT2_IRQ, prvNonPreemptiveTick );
	#endif
}