/*
 * FreeRTOS Kernel V10.2.1
 * Copyright (C) 2019 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.
 *
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 *
 * 1 tab == 4 spaces!
 */


/*-----------------------------------------------------------
 * 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 ( uint16_t ) ( ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) / ( uint32_t ) 4 )

/* From the RDC data sheet. */
#define portENABLE_TIMER_AND_INTERRUPT ( uint16_t ) 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. */
StackType_t *pxPortInitialiseStack(StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters)
{
    StackType_t 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 = (StackType_t) 0xAAAA;    /* AX */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xBBBB;    /* BX */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xCCCC;    /* CX */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xDDDD;    /* DX */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xEEEE;    /* ES */
    pxTopOfStack--;

    /* We need the true data segment. */
    __asm{  MOV DS_Reg, DS };

    *pxTopOfStack = DS_Reg;                     /* DS */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0x0123;    /* SI */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xDDDD;    /* DI */
    pxTopOfStack--;
    *pxTopOfStack = (StackType_t) 0xBBBB;    /* BP */

    return pxTopOfStack;
}
/*-----------------------------------------------------------*/

BaseType_t 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. */
    if (xTaskIncrementTick() != pdFALSE)
    {
        /* 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. */
    xTaskIncrementTick();

    /* 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 uint16_t usTimerACompare = portTIMER_COMPARE, usTimerAMode = portENABLE_TIMER_AND_INTERRUPT;
    const uint16_t 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
}







