/*
 * 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 ARM7 port.
 *
 * Components that can be compiled to either ARM or THUMB mode are
 * contained in this file.  The ISR routines, which can only be compiled
 * to ARM mode are contained in portISR.c.
 *----------------------------------------------------------*/


/* Standard includes. */
#include <stdlib.h>

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

/* Constants required to setup the task context. */
#define portINITIAL_SPSR                ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#define portTHUMB_MODE_BIT              ( ( StackType_t ) 0x20 )
#define portINSTRUCTION_SIZE            ( ( StackType_t ) 4 )
#define portNO_CRITICAL_SECTION_NESTING ( ( StackType_t ) 0 )

/* Constants required to setup the tick ISR. */
#define portENABLE_TIMER                ( ( uint8_t ) 0x01 )
#define portPRESCALE_VALUE              0x00
#define portINTERRUPT_ON_MATCH          ( ( uint32_t ) 0x01 )
#define portRESET_COUNT_ON_MATCH        ( ( uint32_t ) 0x02 )

/* Constants required to setup the VIC for the tick ISR. */
#define portTIMER_VIC_CHANNEL           ( ( uint32_t ) 0x0004 )
#define portTIMER_VIC_CHANNEL_BIT       ( ( uint32_t ) 0x0010 )
#define portTIMER_VIC_ENABLE            ( ( uint32_t ) 0x0020 )

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

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

/*
 * The scheduler can only be started from ARM mode, so
 * vPortISRStartFirstSTask() is defined in portISR.c.
 */
extern void vPortISRStartFirstTask(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) 0x00000000;    /* 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 last thing onto the stack is the status register, which is set for
    system mode, with interrupts enabled. */
    *pxTopOfStack = (StackType_t) portINITIAL_SPSR;

    if (((uint32_t) pxCode & 0x01UL) != 0x00)
    {
        /* We want the task to start in thumb mode. */
        *pxTopOfStack |= portTHUMB_MODE_BIT;
    }

    pxTopOfStack--;

    /* Some optimisation levels use the stack differently to others.  This
    means the 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_SECTION_NESTING;

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

BaseType_t xPortStartScheduler(void)
{
    /* Start the timer that generates the tick ISR.  Interrupts are disabled
    here already. */
    prvSetupTimerInterrupt();

    /* Start the first task. */
    vPortISRStartFirstTask();

    /* 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.  */
}
/*-----------------------------------------------------------*/

/*
 * Setup the timer 0 to generate the tick interrupts at the required frequency.
 */
static void prvSetupTimerInterrupt(void)
{
    uint32_t ulCompareMatch;

    PCLKSEL0 = (PCLKSEL0 & (~(0x3 << 2))) | (0x01 << 2);
    T0TCR  = 2;         /* Stop and reset the timer */
    T0CTCR = 0;         /* Timer mode               */

    /* A 1ms tick does not require the use of the timer prescale.  This is
    defaulted to zero but can be used if necessary. */
    T0PR = portPRESCALE_VALUE;

    /* Calculate the match value required for our wanted tick rate. */
    ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

    /* Protect against divide by zero.  Using an if() statement still results
    in a warning - hence the #if. */
#if portPRESCALE_VALUE != 0
    {
        ulCompareMatch /= (portPRESCALE_VALUE + 1);
    }
#endif
    T0MR1 = ulCompareMatch;

    /* Generate tick with timer 0 compare match. */
    T0MCR  = (3 << 3);  /* Reset timer on match and generate interrupt */

    /* Setup the VIC for the timer. */
    VICIntEnable = 0x00000010;

    /* The ISR installed depends on whether the preemptive or cooperative
    scheduler is being used. */
#if configUSE_PREEMPTION == 1
    {
        extern void (vPreemptiveTick)(void);
        VICVectAddr4 = (int32_t) vPreemptiveTick;
    }
#else
    {
        extern void (vNonPreemptiveTick)(void);
        VICVectAddr4 = (int32_t) vNonPreemptiveTick;
    }
#endif

    VICVectCntl4 = 1;

    /* Start the timer - interrupts are disabled when this function is called
    so it is okay to do this here. */
    T0TCR = portENABLE_TIMER;
}
/*-----------------------------------------------------------*/



