/*
 * 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 SH2A 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 )
#define portINITIAL_FPSW    ( ( StackType_t ) 0x00000100 )

/* These macros allow a critical section to be added around the call to
 * xTaskIncrementTick(), which is only ever called from interrupts at the kernel
 * priority - ie a known priority.  Therefore these local macros are a slight
 * optimisation compared to calling the global SET/CLEAR_INTERRUPT_MASK macros,
 * which would require the old IPL to be read first and stored in a local variable. */
#define portDISABLE_INTERRUPTS_FROM_KERNEL_ISR()    __asm volatile ( "MVTIPL	%0"::"i" ( configMAX_SYSCALL_INTERRUPT_PRIORITY ) )
#define portENABLE_INTERRUPTS_FROM_KERNEL_ISR()     __asm volatile ( "MVTIPL	%0"::"i" ( configKERNEL_INTERRUPT_PRIORITY ) )

/*-----------------------------------------------------------*/

/*
 * Function to start the first task executing - written in asm code as direct
 * access to registers is required.
 */
static void prvStartFirstTask( void ) __attribute__( ( naked ) );

/*
 * Software interrupt handler.  Performs the actual context switch (saving and
 * restoring of registers).  Written in asm code as direct register access is
 * required.
 */
void vSoftwareInterruptISR( void ) __attribute__( ( naked ) );

/*
 * The tick interrupt handler.
 */
void vTickISR( void ) __attribute__( ( interrupt ) );

/*-----------------------------------------------------------*/

extern void * pxCurrentTCB;

/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
                                     TaskFunction_t pxCode,
                                     void * pvParameters )
{
    /* R0 is not included as it is the stack pointer. */

    *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 = 0xffffffff; /* r15. */
            pxTopOfStack--;
            *pxTopOfStack = 0xeeeeeeee;
            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 = portINITIAL_FPSW;
    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();
    }

    /* Should not get here. */
    return pdFAIL;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
    /* Not implemented in ports where there is nothing to return to.
     * Artificially force an assert. */
    configASSERT( pxCurrentTCB == NULL );
}
/*-----------------------------------------------------------*/

static void prvStartFirstTask( void )
{
    __asm volatile
    (

        /* 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						\n"\


        /* Obtain the location of the stack associated with which ever task
         * pxCurrentTCB is currently pointing to. */
        "MOV.L		#_pxCurrentTCB, R15		\n"\
        "MOV.L		[R15], R15				\n"\
        "MOV.L		[R15], R0				\n"\


        /* Restore the registers from the stack of the task pointed to by
         * pxCurrentTCB. */
        "POP		R15						\n"\

        /* Accumulator low 32 bits. */
        "MVTACLO	R15 					\n"\
        "POP		R15						\n"\

        /* Accumulator high 32 bits. */
        "MVTACHI	R15 					\n"\
        "POP		R15						\n"\

        /* Floating point status word. */
        "MVTC		R15, FPSW 				\n"\

        /* R1 to R15 - R0 is not included as it is the SP. */
        "POPM		R1-R15 					\n"\

        /* This pops the remaining registers. */
        "RTE								\n"\
        "NOP								\n"\
        "NOP								\n"
    );
}
/*-----------------------------------------------------------*/

void vSoftwareInterruptISR( void )
{
    __asm volatile
    (
        /* Re-enable interrupts. */
        "SETPSW		I							\n"\


        /* 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							\n"\

        /* Read the user stack pointer. */
        "MVFC		USP, R15					\n"\

        /* Move the address down to the data being moved. */
        "SUB		#12, R15					\n"\
        "MVTC		R15, USP					\n"\

        /* Copy the data across, R15, then PC, then PSW. */
        "MOV.L		[ R0 ], [ R15 ]				\n"\
        "MOV.L 		4[ R0 ], 4[ R15 ]			\n"\
        "MOV.L		8[ R0 ], 8[ R15 ]			\n"\

        /* Move the interrupt stack pointer to its new correct position. */
        "ADD		#12, R0						\n"\

        /* All the rest of the registers are saved directly to the user stack. */
        "SETPSW		U							\n"\

        /* Save the rest of the general registers (R15 has been saved already). */
        "PUSHM		R1-R14						\n"\

        /* Save the FPSW and accumulator. */
        "MVFC		FPSW, R15					\n"\
        "PUSH.L		R15							\n"\
        "MVFACHI 	R15							\n"\
        "PUSH.L		R15							\n"\

        /* Middle word. */
        "MVFACMI	R15							\n"\

        /* Shifted left as it is restored to the low order word. */
        "SHLL		#16, R15					\n"\
        "PUSH.L		R15							\n"\

        /* Save the stack pointer to the TCB. */
        "MOV.L		#_pxCurrentTCB, R15			\n"\
        "MOV.L		[ R15 ], R15				\n"\
        "MOV.L		R0, [ R15 ]					\n"\


        /* Ensure the interrupt mask is set to the syscall priority while the kernel
         * structures are being accessed. */
        "MVTIPL		%0 							\n"\

        /* Select the next task to run. */
        "BSR.A		_vTaskSwitchContext			\n"\

        /* Reset the interrupt mask as no more data structure access is required. */
        "MVTIPL		%1							\n"\


        /* Load the stack pointer of the task that is now selected as the Running
         * state task from its TCB. */
        "MOV.L		#_pxCurrentTCB,R15			\n"\
        "MOV.L		[ R15 ], R15				\n"\
        "MOV.L		[ R15 ], R0					\n"\


        /* Restore the context of the new task.  The PSW (Program Status Word) and
         * PC will be popped by the RTE instruction. */
        "POP		R15							\n"\
        "MVTACLO 	R15							\n"\
        "POP		R15							\n"\
        "MVTACHI 	R15							\n"\
        "POP		R15							\n"\
        "MVTC		R15, FPSW					\n"\
        "POPM		R1-R15						\n"\
        "RTE									\n"\
        "NOP									\n"\
        "NOP									  "
        ::"i" ( configMAX_SYSCALL_INTERRUPT_PRIORITY ), "i" ( configKERNEL_INTERRUPT_PRIORITY )
    );
}
/*-----------------------------------------------------------*/

void vTickISR( void )
{
    /* Re-enabled interrupts. */
    __asm volatile ( "SETPSW	I");

    /* Increment the tick, and perform any processing the new tick value
     * necessitates.  Ensure IPL is at the max syscall value first. */
    portDISABLE_INTERRUPTS_FROM_KERNEL_ISR();
    {
        if( xTaskIncrementTick() != pdFALSE )
        {
            taskYIELD();
        }
    }
    portENABLE_INTERRUPTS_FROM_KERNEL_ISR();
}
/*-----------------------------------------------------------*/

uint32_t ulPortGetIPL( void )
{
    __asm volatile
    (
        "MVFC	PSW, R1			\n"\
        "SHLR	#24, R1			\n"\
        "RTS					  "
    );

    /* This will never get executed, but keeps the compiler from complaining. */
    return 0;
}
/*-----------------------------------------------------------*/

void vPortSetIPL( uint32_t ulNewIPL )
{
    __asm volatile
    (
        "PUSH	R5				\n"\
        "MVFC	PSW, R5			\n"\
        "SHLL	#24, R1			\n"\
        "AND	#-0F000001H, R5 \n"\
        "OR		R1, R5			\n"\
        "MVTC	R5, PSW			\n"\
        "POP	R5				\n"\
        "RTS					  "
    );
}