;/*
;    FreeRTOS V8.1.0 - Copyright (C) 2014 Real Time Engineers Ltd.
;    All rights reserved
;
;
;    ***************************************************************************
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;
;
;    This file is part of the FreeRTOS distribution.
;
;    FreeRTOS is free software; you can redistribute it and/or modify it under
;    the terms of the GNU General Public License (version 2) as published by the
;    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
;    >>>NOTE<<< The modification to the GPL is included to allow you to
;    distribute a combined work that includes FreeRTOS without being obliged to
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;    more details. You should have received a copy of the GNU General Public
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;    by writing to Richard Barry, contact details for whom are available on the
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;*/

	INCLUDE portmacro.inc

	IMPORT	vApplicationIRQHandler
	IMPORT	vTaskSwitchContext
	IMPORT	ulPortYieldRequired
	IMPORT	ulPortInterruptNesting
	IMPORT	vTaskSwitchContext
	IMPORT	ulICCIAR
	IMPORT	ulICCEOIR

	EXPORT	FreeRTOS_SWI_Handler
	EXPORT  FreeRTOS_IRQ_Handler
	EXPORT 	vPortRestoreTaskContext

	ARM
	AREA	PORT_ASM, CODE, READONLY


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; SVC handler is used to yield a task.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
FreeRTOS_SWI_Handler

	PRESERVE8

	; Save the context of the current task and select a new task to run.
	portSAVE_CONTEXT
	LDR R0, =vTaskSwitchContext
	BLX	R0
	portRESTORE_CONTEXT

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; vPortRestoreTaskContext is used to start the scheduler.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
vPortRestoreTaskContext
	; Switch to system mode
	CPS		#SYS_MODE
	portRESTORE_CONTEXT

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; PL390 GIC interrupt handler
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
FreeRTOS_IRQ_Handler

	; Return to the interrupted instruction.
	SUB		lr, lr, #4

	; Push the return address and SPSR
	PUSH	{lr}
	MRS		lr, SPSR
	PUSH	{lr}

	; Change to supervisor mode to allow reentry.
	CPS		#SVC_MODE

	; Push used registers.
	PUSH	{r0-r4, r12}

	; Increment nesting count.  r3 holds the address of ulPortInterruptNesting
	; for future use.  r1 holds the original ulPortInterruptNesting value for
	; future use.
	LDR		r3, =ulPortInterruptNesting
	LDR		r1, [r3]
	ADD		r4, r1, #1
	STR		r4, [r3]

	; Read value from the interrupt acknowledge register, which is stored in r0
	; for future parameter and interrupt clearing use.
	LDR 	r2, =ulICCIAR
	LDR		r0, [r2]

	; Ensure bit 2 of the stack pointer is clear.  r2 holds the bit 2 value for
	; future use.
	MOV		r2, sp
	AND		r2, r2, #4
	SUB		sp, sp, r2

	; Call the interrupt handler
	PUSH	{r0-r3, lr}
	LDR		r1, =vApplicationIRQHandler
	BLX		r1
	POP		{r0-r3, lr}
	ADD		sp, sp, r2

	CPSID 	i

	; Write the value read from ICCIAR to ICCEOIR
	LDR 	r4, =ulICCEOIR
	STR		r0, [r4]

	; Restore the old nesting count
	STR		r1, [r3]

	; A context switch is never performed if the nesting count is not 0
	CMP		r1, #0
	BNE		exit_without_switch

	; Did the interrupt request a context switch?  r1 holds the address of
	; ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
	; use.
	LDR		r1, =ulPortYieldRequired
	LDR		r0, [r1]
	CMP		r0, #0
	BNE		switch_before_exit

exit_without_switch
	; No context switch.  Restore used registers, LR_irq and SPSR before
	; returning.
	POP		{r0-r4, r12}
	CPS		#IRQ_MODE
	POP		{LR}
	MSR		SPSR_cxsf, LR
	POP		{LR}
	MOVS	PC, LR

switch_before_exit
	; A context swtich is to be performed.  Clear the context switch pending
	; flag.
	MOV		r0, #0
	STR		r0, [r1]

	; Restore used registers, LR-irq and SPSR before saving the context
	; to the task stack.
	POP		{r0-r4, r12}
	CPS		#IRQ_MODE
	POP		{LR}
	MSR		SPSR_cxsf, LR
	POP		{LR}
	portSAVE_CONTEXT

	; Call the function that selects the new task to execute.
	; vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
	; instructions, or 8 byte aligned stack allocated data.  LR does not need
	; saving as a new LR will be loaded by portRESTORE_CONTEXT anyway.
	LDR		r0, =vTaskSwitchContext
	BLX		r0

	; Restore the context of, and branch to, the task selected to execute next.
	portRESTORE_CONTEXT


	END