/*
 * FreeRTOS Kernel V10.3.1
 * 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.
 *
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 *
 * 1 tab == 4 spaces!
 */

/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the RX200 port.
*----------------------------------------------------------*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Library includes. */
#include "string.h"

/* Hardware specifics. */
#include "iodefine.h"

/*-----------------------------------------------------------*/

/* Tasks should start with interrupts enabled and in Supervisor mode, therefore
 * PSW is set with U and I set, and PM and IPL clear. */
#define portINITIAL_PSW    ( ( StackType_t ) 0x00030000 )

/*-----------------------------------------------------------*/

/* The following lines are to ensure vSoftwareInterruptEntry can be referenced,
 * and therefore installed in the vector table, when the FreeRTOS code is built
 * as a library. */
extern BaseType_t vSoftwareInterruptEntry;
const BaseType_t * p_vSoftwareInterruptEntry = &vSoftwareInterruptEntry;

/*-----------------------------------------------------------*/

/*
 * Function to start the first task executing - written in asm code as direct
 * access to registers is required.
 */
static void prvStartFirstTask( void );

/*
 * Software interrupt handler.  Performs the actual context switch (saving and
 * restoring of registers).  Written in asm code as direct register access is
 * required.
 */
static void prvYieldHandler( void );

/*
 * The entry point for the software interrupt handler.  This is the function
 * that calls the inline asm function prvYieldHandler().  It is installed in
 * the vector table, but the code that installs it is in prvYieldHandler rather
 * than using a #pragma.
 */
void vSoftwareInterruptISR( void );

/*-----------------------------------------------------------*/

/* This is accessed by the inline assembler functions so is file scope for
 * convenience. */
extern void * pxCurrentTCB;
extern void vTaskSwitchContext( void );

/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
                                     TaskFunction_t pxCode,
                                     void * pvParameters )
{
    /* Offset to end up on 8 byte boundary. */
    pxTopOfStack--;

    /* R0 is not included as it is the stack pointer. */
    *pxTopOfStack = 0x00;
    pxTopOfStack--;
    *pxTopOfStack = 0x00;
    pxTopOfStack--;
    *pxTopOfStack = portINITIAL_PSW;
    pxTopOfStack--;
    *pxTopOfStack = ( StackType_t ) pxCode;

    /* When debugging it can be useful if every register is set to a known
     * value.  Otherwise code space can be saved by just setting the registers
     * that need to be set. */
    #ifdef USE_FULL_REGISTER_INITIALISATION
        {
            pxTopOfStack--;
            *pxTopOfStack = 0x12345678; /* r15. */
            pxTopOfStack--;
            *pxTopOfStack = 0xaaaabbbb;
            pxTopOfStack--;
            *pxTopOfStack = 0xdddddddd;
            pxTopOfStack--;
            *pxTopOfStack = 0xcccccccc;
            pxTopOfStack--;
            *pxTopOfStack = 0xbbbbbbbb;
            pxTopOfStack--;
            *pxTopOfStack = 0xaaaaaaaa;
            pxTopOfStack--;
            *pxTopOfStack = 0x99999999;
            pxTopOfStack--;
            *pxTopOfStack = 0x88888888;
            pxTopOfStack--;
            *pxTopOfStack = 0x77777777;
            pxTopOfStack--;
            *pxTopOfStack = 0x66666666;
            pxTopOfStack--;
            *pxTopOfStack = 0x55555555;
            pxTopOfStack--;
            *pxTopOfStack = 0x44444444;
            pxTopOfStack--;
            *pxTopOfStack = 0x33333333;
            pxTopOfStack--;
            *pxTopOfStack = 0x22222222;
            pxTopOfStack--;
        }
    #else /* ifdef USE_FULL_REGISTER_INITIALISATION */
        {
            pxTopOfStack -= 15;
        }
    #endif /* ifdef USE_FULL_REGISTER_INITIALISATION */

    *pxTopOfStack = ( StackType_t ) pvParameters; /* R1 */
    pxTopOfStack--;
    *pxTopOfStack = 0x12345678;                   /* Accumulator. */
    pxTopOfStack--;
    *pxTopOfStack = 0x87654321;                   /* Accumulator. */

    return pxTopOfStack;
}
/*-----------------------------------------------------------*/

BaseType_t xPortStartScheduler( void )
{
    extern void vApplicationSetupTimerInterrupt( void );

    /* Use pxCurrentTCB just so it does not get optimised away. */
    if( pxCurrentTCB != NULL )
    {
        /* Call an application function to set up the timer that will generate the
         * tick interrupt.  This way the application can decide which peripheral to
         * use.  A demo application is provided to show a suitable example. */
        vApplicationSetupTimerInterrupt();

        /* Enable the software interrupt. */
        _IEN( _ICU_SWINT ) = 1;

        /* Ensure the software interrupt is clear. */
        _IR( _ICU_SWINT ) = 0;

        /* Ensure the software interrupt is set to the kernel priority. */
        _IPR( _ICU_SWINT ) = configKERNEL_INTERRUPT_PRIORITY;

        /* Start the first task. */
        prvStartFirstTask();
    }

    /* Just to make sure the function is not optimised away. */
    ( void ) vSoftwareInterruptISR();

    /* Should not get here. */
    return pdFAIL;
}
/*-----------------------------------------------------------*/

#pragma inline_asm prvStartFirstTask
static void prvStartFirstTask( void )
{
    /* When starting the scheduler there is nothing that needs moving to the
     * interrupt stack because the function is not called from an interrupt.
     * Just ensure the current stack is the user stack. */
    SETPSW U

    /* Obtain the location of the stack associated with which ever task
     * pxCurrentTCB is currently pointing to. */
    MOV.L   # _pxCurrentTCB, R15
        MOV.L[ R15 ], R15
        MOV.L[ R15 ], R0

    /* Restore the registers from the stack of the task pointed to by
     * pxCurrentTCB. */
    POP R15
    MVTACLO R15   /* Accumulator low 32 bits. */
    POP R15
    MVTACHI R15   /* Accumulator high 32 bits. */
    POPM R1 - R15 /* R1 to R15 - R0 is not included as it is the SP. */
    RTE           /* This pops the remaining registers. */
    NOP
        NOP
}
/*-----------------------------------------------------------*/

#pragma interrupt ( vTickISR( vect = _VECT( configTICK_VECTOR ), enable ) )
void vTickISR( void )
{
    /* Increment the tick, and perform any processing the new tick value
     * necessitates. */
    set_ipl( configMAX_SYSCALL_INTERRUPT_PRIORITY );
    {
        if( xTaskIncrementTick() != pdFALSE )
        {
            taskYIELD();
        }
    }

    set_ipl( configKERNEL_INTERRUPT_PRIORITY );
}
/*-----------------------------------------------------------*/

void vSoftwareInterruptISR( void )
{
    prvYieldHandler();
}
/*-----------------------------------------------------------*/

#pragma inline_asm prvYieldHandler
static void prvYieldHandler( void )
{
    /* Re-enable interrupts. */
    SETPSW I

    /* Move the data that was automatically pushed onto the interrupt stack when
     * the interrupt occurred from the interrupt stack to the user stack.
     *
     * R15 is saved before it is clobbered. */
    PUSH.L R15

    /* Read the user stack pointer. */
    MVFC USP, R15

    /* Move the address down to the data being moved. */
         SUB     # 12, R15
    MVTC R15, USP

    /* Copy the data across. */
         MOV.L[ R0 ], [ R15 ];
    R15

    MOV.L   4[ R0 ], 4[ R15 ];
    PC
    MOV.L   8[ R0 ], 8[ R15 ];
    PSW

    /* Move the interrupt stack pointer to its new correct position. */
        ADD # 12, R0

    /* All the rest of the registers are saved directly to the user stack. */
    SETPSW U

    /* Save the rest of the general registers (R15 has been saved already). */
    PUSHM R1 - R14

    /* Save the accumulator. */
    MVFACHI R15
        PUSH.L R15
    MVFACMI R15;
    Middle order word.
       SHLL    # 16, R15;
    Shifted left as it is restored to the low order word.
       PUSH.L R15

    /* Save the stack pointer to the TCB. */
    MOV.L   # _pxCurrentTCB, R15
        MOV.L[ R15 ], R15
        MOV.L R0, [ R15 ]

    /* Ensure the interrupt mask is set to the syscall priority while the kernel
     * structures are being accessed. */
    MVTIPL  # configMAX_SYSCALL_INTERRUPT_PRIORITY

    /* Select the next task to run. */
    BSR.A _vTaskSwitchContext

    /* Reset the interrupt mask as no more data structure access is required. */
    MVTIPL  # configKERNEL_INTERRUPT_PRIORITY

    /* Load the stack pointer of the task that is now selected as the Running
     * state task from its TCB. */
    MOV.L   # _pxCurrentTCB, R15
        MOV.L[ R15 ], R15
        MOV.L[ R15 ], R0

    /* Restore the context of the new task.  The PSW (Program Status Word) and
     * PC will be popped by the RTE instruction. */
    POP R15
    MVTACLO R15
    POP R15
    MVTACHI R15
    POPM R1 - R15
    RTE
    NOP
        NOP
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
    /* Not implemented in ports where there is nothing to return to.
     * Artificially force an assert. */
    configASSERT( pxCurrentTCB == NULL );

    /* The following line is just to prevent the symbol getting optimised away. */
    ( void ) vTaskSwitchContext();
}
/*-----------------------------------------------------------*/