/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * 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.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the Atmel ARM7 port.
 *----------------------------------------------------------*/


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

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

/* Constants required to setup the initial stack. */
#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 )

/* Constants required to setup the PIT. */
#define portPIT_CLOCK_DIVISOR           ( ( uint32_t ) 16 )
#define portPIT_COUNTER_VALUE           ( ( ( configCPU_CLOCK_HZ / portPIT_CLOCK_DIVISOR ) / 1000UL ) * portTICK_PERIOD_MS )

/* Constants required to handle critical sections. */
#define portNO_CRITICAL_NESTING         ( ( uint32_t ) 0 )


#define portINT_LEVEL_SENSITIVE  0
#define portPIT_ENABLE          ( ( uint16_t ) 0x1 << 24 )
#define portPIT_INT_ENABLE      ( ( uint16_t ) 0x1 << 25 )
/*-----------------------------------------------------------*/

/* Setup the PIT 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;

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

/*
 * 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;

    if( ( ( uint32_t ) pxCode & 0x01UL ) != 0x00UL )
    {
        /* We want the task to start in thumb mode. */
        *pxTopOfStack |= portTHUMB_MODE_BIT;
    }

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

#if configUSE_PREEMPTION == 0

    /* The cooperative scheduler requires a normal IRQ service routine to
    simply increment the system tick. */
    static __arm __irq void vPortNonPreemptiveTick( void );
    static __arm __irq void vPortNonPreemptiveTick( void )
    {
        uint32_t ulDummy;

        /* Increment the tick count - which may wake some tasks but as the
        preemptive scheduler is not being used any woken task is not given
        processor time no matter what its priority. */
        xTaskIncrementTick();

        /* Clear the PIT interrupt. */
        ulDummy = AT91C_BASE_PITC->PITC_PIVR;

        /* End the interrupt in the AIC. */
        AT91C_BASE_AIC->AIC_EOICR = ulDummy;
    }

#else

    /* Currently the IAR port requires the preemptive tick function to be
    defined in an asm file. */

#endif

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

static void prvSetupTimerInterrupt( void )
{
AT91PS_PITC pxPIT = AT91C_BASE_PITC;

    /* Setup the AIC for PIT interrupts.  The interrupt routine chosen depends
    on whether the preemptive or cooperative scheduler is being used. */
    #if configUSE_PREEMPTION == 0

        AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortNonPreemptiveTick );

    #else

        extern void ( vPortPreemptiveTick )( void );
        AT91F_AIC_ConfigureIt( AT91C_BASE_AIC, AT91C_ID_SYS, AT91C_AIC_PRIOR_HIGHEST, portINT_LEVEL_SENSITIVE, ( void (*)(void) ) vPortPreemptiveTick );

    #endif

    /* Configure the PIT period. */
    pxPIT->PITC_PIMR = portPIT_ENABLE | portPIT_INT_ENABLE | portPIT_COUNTER_VALUE;

    /* Enable the interrupt.  Global interrupts are disables at this point so
    this is safe. */
    AT91F_AIC_EnableIt( AT91C_BASE_AIC, AT91C_ID_SYS );
}
/*-----------------------------------------------------------*/

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++;
}
/*-----------------------------------------------------------*/

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();
        }
    }
}
/*-----------------------------------------------------------*/