/*
 * 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
 *
 */

/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the ST STR75x ARM7
* port.
*----------------------------------------------------------*/

/* Library includes. */
#include "75x_tb.h"
#include "75x_eic.h"

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Constants required to setup the initial stack. */
#define portINITIAL_SPSR           ( ( StackType_t ) 0x3f )      /* System mode, THUMB mode, interrupts enabled. */
#define portINSTRUCTION_SIZE       ( ( StackType_t ) 4 )

/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING    ( ( uint32_t ) 0 )

/* Prescale used on the timer clock when calculating the tick period. */
#define portPRESCALE               20


/*-----------------------------------------------------------*/

/* Setup the TB 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 preemptive operation. */
__arm 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;
    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.  */
}
/*-----------------------------------------------------------*/

__arm void vPortPreemptiveTick( void )
{
    /* Increment the tick counter. */
    if( xTaskIncrementTick() != pdFALSE )
    {
        /* Select a new task to execute. */
        vTaskSwitchContext();
    }

    TB_ClearITPendingBit( TB_IT_Update );
}
/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )
{
    EIC_IRQInitTypeDef EIC_IRQInitStructure;
    TB_InitTypeDef     TB_InitStructure;

    /* Setup the EIC for the TB. */
    EIC_IRQInitStructure.EIC_IRQChannelCmd      = ENABLE;
    EIC_IRQInitStructure.EIC_IRQChannel         = TB_IRQChannel;
    EIC_IRQInitStructure.EIC_IRQChannelPriority = 1;
    EIC_IRQInit( &EIC_IRQInitStructure );

    /* Setup the TB for the generation of the tick interrupt. */
    TB_InitStructure.TB_Mode                    = TB_Mode_Timing;
    TB_InitStructure.TB_CounterMode             = TB_CounterMode_Down;
    TB_InitStructure.TB_Prescaler               = portPRESCALE - 1;
    TB_InitStructure.TB_AutoReload              = ( ( configCPU_CLOCK_HZ / portPRESCALE ) / configTICK_RATE_HZ );
    TB_Init( &TB_InitStructure );

    /* Enable TB Update interrupt */
    TB_ITConfig( TB_IT_Update, ENABLE );

    /* Clear TB Update interrupt pending bit */
    TB_ClearITPendingBit( TB_IT_Update );

    /* Enable TB */
    TB_Cmd( 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();
        }
    }
}
/*-----------------------------------------------------------*/