/*
 * 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
 *
 */

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

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

#ifndef configINTERRUPT_CONTROLLER_BASE_ADDRESS
    #error configINTERRUPT_CONTROLLER_BASE_ADDRESS must be defined.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET
    #error configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET must be defined.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configUNIQUE_INTERRUPT_PRIORITIES
    #error configUNIQUE_INTERRUPT_PRIORITIES must be defined.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#ifndef configSETUP_TICK_INTERRUPT
    #error configSETUP_TICK_INTERRUPT() must be defined.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif /* configSETUP_TICK_INTERRUPT */

#ifndef configMAX_API_CALL_INTERRUPT_PRIORITY
    #error configMAX_API_CALL_INTERRUPT_PRIORITY must be defined.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-Cortex-A-Embedded-Processors.html
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY == 0
    #error configMAX_API_CALL_INTERRUPT_PRIORITY must not be set to 0
#endif

#if configMAX_API_CALL_INTERRUPT_PRIORITY > configUNIQUE_INTERRUPT_PRIORITIES
    #error configMAX_API_CALL_INTERRUPT_PRIORITY must be less than or equal to configUNIQUE_INTERRUPT_PRIORITIES as the lower the numeric priority value the higher the logical interrupt priority
#endif

#if configUSE_PORT_OPTIMISED_TASK_SELECTION == 1
    /* Check the configuration. */
    #if( configMAX_PRIORITIES > 32 )
        #error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32.  It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
    #endif
#endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */

/* In case security extensions are implemented. */
#if configMAX_API_CALL_INTERRUPT_PRIORITY <= ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
    #error configMAX_API_CALL_INTERRUPT_PRIORITY must be greater than ( configUNIQUE_INTERRUPT_PRIORITIES / 2 )
#endif

#ifndef configCLEAR_TICK_INTERRUPT
    #define configCLEAR_TICK_INTERRUPT()
#endif

/* The number of bits to shift for an interrupt priority is dependent on the
number of bits implemented by the interrupt controller. */
#if configUNIQUE_INTERRUPT_PRIORITIES == 16
    #define portPRIORITY_SHIFT 4
    #define portMAX_BINARY_POINT_VALUE  3
#elif configUNIQUE_INTERRUPT_PRIORITIES == 32
    #define portPRIORITY_SHIFT 3
    #define portMAX_BINARY_POINT_VALUE  2
#elif configUNIQUE_INTERRUPT_PRIORITIES == 64
    #define portPRIORITY_SHIFT 2
    #define portMAX_BINARY_POINT_VALUE  1
#elif configUNIQUE_INTERRUPT_PRIORITIES == 128
    #define portPRIORITY_SHIFT 1
    #define portMAX_BINARY_POINT_VALUE  0
#elif configUNIQUE_INTERRUPT_PRIORITIES == 256
    #define portPRIORITY_SHIFT 0
    #define portMAX_BINARY_POINT_VALUE  0
#else
    #error Invalid configUNIQUE_INTERRUPT_PRIORITIES setting.  configUNIQUE_INTERRUPT_PRIORITIES must be set to the number of unique priorities implemented by the target hardware
#endif

/* A critical section is exited when the critical section nesting count reaches
this value. */
#define portNO_CRITICAL_NESTING         ( ( uint32_t ) 0 )

/* In all GICs 255 can be written to the priority mask register to unmask all
(but the lowest) interrupt priority. */
#define portUNMASK_VALUE                ( 0xFFUL )

/* Tasks are not created with a floating point context, but can be given a
floating point context after they have been created.  A variable is stored as
part of the tasks context that holds portNO_FLOATING_POINT_CONTEXT if the task
does not have an FPU context, or any other value if the task does have an FPU
context. */
#define portNO_FLOATING_POINT_CONTEXT   ( ( StackType_t ) 0 )

/* Interrupt controller access addresses. */
#define portICCPMR_PRIORITY_MASK_OFFSET         ( 0x04 )
#define portICCIAR_INTERRUPT_ACKNOWLEDGE_OFFSET ( 0x0C )
#define portICCEOIR_END_OF_INTERRUPT_OFFSET     ( 0x10 )
#define portICCBPR_BINARY_POINT_OFFSET          ( 0x08 )
#define portICCRPR_RUNNING_PRIORITY_OFFSET      ( 0x14 )
#define portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS      ( configINTERRUPT_CONTROLLER_BASE_ADDRESS + configINTERRUPT_CONTROLLER_CPU_INTERFACE_OFFSET )
#define portICCPMR_PRIORITY_MASK_REGISTER                   ( *( ( volatile uint32_t * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCPMR_PRIORITY_MASK_OFFSET ) ) )
#define portICCIAR_INTERRUPT_ACKNOWLEDGE_REGISTER_ADDRESS   ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCIAR_INTERRUPT_ACKNOWLEDGE_OFFSET )
#define portICCEOIR_END_OF_INTERRUPT_REGISTER_ADDRESS       ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCEOIR_END_OF_INTERRUPT_OFFSET )
#define portICCPMR_PRIORITY_MASK_REGISTER_ADDRESS           ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCPMR_PRIORITY_MASK_OFFSET )
#define portICCBPR_BINARY_POINT_REGISTER                    ( *( ( const volatile uint32_t * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCBPR_BINARY_POINT_OFFSET ) ) )
#define portICCRPR_RUNNING_PRIORITY_REGISTER                ( *( ( const volatile uint32_t * ) ( portINTERRUPT_CONTROLLER_CPU_INTERFACE_ADDRESS + portICCRPR_RUNNING_PRIORITY_OFFSET ) ) )

/* Used by portASSERT_IF_INTERRUPT_PRIORITY_INVALID() when ensuring the binary
point is zero. */
#define portBINARY_POINT_BITS           ( ( uint8_t ) 0x03 )

/* Constants required to setup the initial task context. */
#define portINITIAL_SPSR                ( ( StackType_t ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#define portTHUMB_MODE_BIT              ( ( StackType_t ) 0x20 )
#define portTHUMB_MODE_ADDRESS          ( 0x01UL )

/* Masks all bits in the APSR other than the mode bits. */
#define portAPSR_MODE_BITS_MASK         ( 0x1F )

/* The value of the mode bits in the APSR when the CPU is executing in user
mode. */
#define portAPSR_USER_MODE              ( 0x10 )

/* Macro to unmask all interrupt priorities. */
#define portCLEAR_INTERRUPT_MASK()                                          \
{                                                                           \
    __disable_irq();                                                        \
    portICCPMR_PRIORITY_MASK_REGISTER = portUNMASK_VALUE;                   \
    __asm(  "DSB        \n"                                                 \
            "ISB        \n" );                                              \
    __enable_irq();                                                         \
}

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

/*
 * Starts the first task executing.  This function is necessarily written in
 * assembly code so is implemented in portASM.s.
 */
extern void vPortRestoreTaskContext( void );

/*
 * Used to catch tasks that attempt to return from their implementing function.
 */
static void prvTaskExitError( void );

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

/* A variable is used to keep track of the critical section nesting.  This
variable has to be stored as part of the task context and must be initialised to
a non zero value to ensure interrupts don't inadvertently become unmasked before
the scheduler starts.  As it is stored as part of the task context it will
automatically be set to 0 when the first task is started. */
volatile uint32_t ulCriticalNesting = 9999UL;

/* Used to pass constants into the ASM code.  The address at which variables are
placed is the constant value so indirect loads in the asm code are not
required. */
uint32_t ulICCIAR __attribute__( ( at( portICCIAR_INTERRUPT_ACKNOWLEDGE_REGISTER_ADDRESS ) ) );
uint32_t ulICCEOIR __attribute__( ( at( portICCEOIR_END_OF_INTERRUPT_REGISTER_ADDRESS ) ) );
uint32_t ulICCPMR __attribute__( ( at( portICCPMR_PRIORITY_MASK_REGISTER_ADDRESS ) ) );
uint32_t ulAsmAPIPriorityMask __attribute__( ( at( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) ) );

/* Saved as part of the task context.  If ulPortTaskHasFPUContext is non-zero then
a floating point context must be saved and restored for the task. */
uint32_t ulPortTaskHasFPUContext = pdFALSE;

/* Set to 1 to pend a context switch from an ISR. */
uint32_t ulPortYieldRequired = pdFALSE;

/* Counts the interrupt nesting depth.  A context switch is only performed if
if the nesting depth is 0. */
uint32_t ulPortInterruptNesting = 0UL;

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

/*
 * See header file for description.
 */
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
{
    /* Setup the initial stack of the task.  The stack is set exactly as
    expected by the portRESTORE_CONTEXT() macro.

    The fist real value on the stack is the status register, which is set for
    system mode, with interrupts enabled.  A few NULLs are added first to ensure
    GDB does not try decoding a non-existent return address. */
    *pxTopOfStack = NULL;
    pxTopOfStack--;
    *pxTopOfStack = NULL;
    pxTopOfStack--;
    *pxTopOfStack = NULL;
    pxTopOfStack--;
    *pxTopOfStack = ( StackType_t ) portINITIAL_SPSR;

    if( ( ( uint32_t ) pxCode & portTHUMB_MODE_ADDRESS ) != 0x00UL )
    {
        /* The task will start in THUMB mode. */
        *pxTopOfStack |= portTHUMB_MODE_BIT;
    }

    pxTopOfStack--;

    /* Next the return address, which in this case is the start of the task. */
    *pxTopOfStack = ( StackType_t ) pxCode;
    pxTopOfStack--;

    /* Next all the registers other than the stack pointer. */
    *pxTopOfStack = ( StackType_t ) prvTaskExitError;   /* R14 */
    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--;
    *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
    pxTopOfStack--;

    /* The task will start with a critical nesting count of 0 as interrupts are
    enabled. */
    *pxTopOfStack = portNO_CRITICAL_NESTING;
    pxTopOfStack--;

    /* The task will start without a floating point context.  A task that uses
    the floating point hardware must call vPortTaskUsesFPU() before executing
    any floating point instructions. */
    *pxTopOfStack = portNO_FLOATING_POINT_CONTEXT;

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

static void prvTaskExitError( void )
{
    /* A function that implements a task must not exit or attempt to return to
    its caller as there is nothing to return to.  If a task wants to exit it
    should instead call vTaskDelete( NULL ).

    Artificially force an assert() to be triggered if configASSERT() is
    defined, then stop here so application writers can catch the error. */
    configASSERT( ulPortInterruptNesting == ~0UL );
    portDISABLE_INTERRUPTS();
    for( ;; );
}
/*-----------------------------------------------------------*/

BaseType_t xPortStartScheduler( void )
{
uint32_t ulAPSR;

    /* Only continue if the CPU is not in User mode.  The CPU must be in a
    Privileged mode for the scheduler to start. */
    __asm( "MRS ulAPSR, APSR" );
    ulAPSR &= portAPSR_MODE_BITS_MASK;
    configASSERT( ulAPSR != portAPSR_USER_MODE );

    if( ulAPSR != portAPSR_USER_MODE )
    {
        /* Only continue if the binary point value is set to its lowest possible
        setting.  See the comments in vPortValidateInterruptPriority() below for
        more information. */
        configASSERT( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE );

        if( ( portICCBPR_BINARY_POINT_REGISTER & portBINARY_POINT_BITS ) <= portMAX_BINARY_POINT_VALUE )
        {
            /* Start the timer that generates the tick ISR. */
            configSETUP_TICK_INTERRUPT();

            __enable_irq();
            vPortRestoreTaskContext();
        }
    }

    /* Will only get here if vTaskStartScheduler() was called with the CPU in
    a non-privileged mode or the binary point register was not set to its lowest
    possible value. */
    return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
    /* Not implemented in ports where there is nothing to return to.
    Artificially force an assert. */
    configASSERT( ulCriticalNesting == 1000UL );
}
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
    /* Disable interrupts as per portDISABLE_INTERRUPTS();  */
    ulPortSetInterruptMask();

    /* 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++;

    /* This is not the interrupt safe version of the enter critical function so
    assert() if it is being called from an interrupt context.  Only API
    functions that end in "FromISR" can be used in an interrupt.  Only assert if
    the critical nesting count is 1 to protect against recursive calls if the
    assert function also uses a critical section. */
    if( ulCriticalNesting == 1 )
    {
        configASSERT( ulPortInterruptNesting == 0 );
    }
}
/*-----------------------------------------------------------*/

void vPortExitCritical( void )
{
    if( ulCriticalNesting > portNO_CRITICAL_NESTING )
    {
        /* Decrement the nesting count as the critical section is being
        exited. */
        ulCriticalNesting--;

        /* If the nesting level has reached zero then all interrupt
        priorities must be re-enabled. */
        if( ulCriticalNesting == portNO_CRITICAL_NESTING )
        {
            /* Critical nesting has reached zero so all interrupt priorities
            should be unmasked. */
            portCLEAR_INTERRUPT_MASK();
        }
    }
}
/*-----------------------------------------------------------*/

void FreeRTOS_Tick_Handler( void )
{
    /* Set interrupt mask before altering scheduler structures.   The tick
    handler runs at the lowest priority, so interrupts cannot already be masked,
    so there is no need to save and restore the current mask value. */
    __disable_irq();
    portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
    __asm(  "DSB        \n"
            "ISB        \n" );
    __enable_irq();

    /* Increment the RTOS tick. */
    if( xTaskIncrementTick() != pdFALSE )
    {
        ulPortYieldRequired = pdTRUE;
    }

    /* Ensure all interrupt priorities are active again. */
    portCLEAR_INTERRUPT_MASK();
    configCLEAR_TICK_INTERRUPT();
}
/*-----------------------------------------------------------*/

void vPortTaskUsesFPU( void )
{
uint32_t ulInitialFPSCR = 0;

    /* A task is registering the fact that it needs an FPU context.  Set the
    FPU flag (which is saved as part of the task context). */
    ulPortTaskHasFPUContext = pdTRUE;

    /* Initialise the floating point status register. */
    __asm( "FMXR    FPSCR, ulInitialFPSCR" );
}
/*-----------------------------------------------------------*/

void vPortClearInterruptMask( uint32_t ulNewMaskValue )
{
    if( ulNewMaskValue == pdFALSE )
    {
        portCLEAR_INTERRUPT_MASK();
    }
}
/*-----------------------------------------------------------*/

uint32_t ulPortSetInterruptMask( void )
{
uint32_t ulReturn;

    __disable_irq();
    if( portICCPMR_PRIORITY_MASK_REGISTER == ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) )
    {
        /* Interrupts were already masked. */
        ulReturn = pdTRUE;
    }
    else
    {
        ulReturn = pdFALSE;
        portICCPMR_PRIORITY_MASK_REGISTER = ( uint32_t ) ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT );
        __asm(  "DSB        \n"
                "ISB        \n" );
    }
    __enable_irq();

    return ulReturn;
}
/*-----------------------------------------------------------*/

#if( configASSERT_DEFINED == 1 )

    void vPortValidateInterruptPriority( void )
    {
        /* The following assertion will fail if a service routine (ISR) for
        an interrupt that has been assigned a priority above
        configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
        function.  ISR safe FreeRTOS API functions must *only* be called
        from interrupts that have been assigned a priority at or below
        configMAX_SYSCALL_INTERRUPT_PRIORITY.

        Numerically low interrupt priority numbers represent logically high
        interrupt priorities, therefore the priority of the interrupt must
        be set to a value equal to or numerically *higher* than
        configMAX_SYSCALL_INTERRUPT_PRIORITY.

        FreeRTOS maintains separate thread and ISR API functions to ensure
        interrupt entry is as fast and simple as possible.

        The following links provide detailed information:
        https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html
        https://www.FreeRTOS.org/FAQHelp.html */
        configASSERT( portICCRPR_RUNNING_PRIORITY_REGISTER >= ( configMAX_API_CALL_INTERRUPT_PRIORITY << portPRIORITY_SHIFT ) );

        /* Priority grouping:  The interrupt controller (GIC) allows the bits
        that define each interrupt's priority to be split between bits that
        define the interrupt's pre-emption priority bits and bits that define
        the interrupt's sub-priority.  For simplicity all bits must be defined
        to be pre-emption priority bits.  The following assertion will fail if
        this is not the case (if some bits represent a sub-priority).

        The priority grouping is configured by the GIC's binary point register
        (ICCBPR).  Writting 0 to ICCBPR will ensure it is set to its lowest
        possible value (which may be above 0). */
        configASSERT( portICCBPR_BINARY_POINT_REGISTER <= portMAX_BINARY_POINT_VALUE );
    }

#endif /* configASSERT_DEFINED */