/*
    FreeRTOS V8.2.2 - Copyright (C) 2015 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    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 provide the source code for proprietary components     !<<
    >>!   outside of the FreeRTOS kernel.                                   !<<
    ***************************************************************************

    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS provides completely free yet professionally developed,    *
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     *    is the industry's de facto standard.                               *
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    ***************************************************************************

    http://www.FreeRTOS.org/FAQHelp.html - Having a problem?  Start by reading
    the FAQ page "My application does not run, what could be wrong?".  Have you
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    http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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    http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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    1 tab == 4 spaces!
*/

#include "FreeRTOSConfig.h"

#define portCONTEXT_SIZE 132
#define portEPC_STACK_LOCATION	124
#define portSTATUS_STACK_LOCATION 128

/******************************************************************/
.macro	portSAVE_CONTEXT

	/* Make room for the context. First save the current status so it can be
	manipulated, and the cause and EPC registers so their original values are
	captured. */
	mfc0		k0, _CP0_CAUSE
	addiu		sp,	sp, -portCONTEXT_SIZE
	mfc0		k1, _CP0_STATUS

	/* Also save s6 and s5 so they can be used.  Any nesting interrupts should
	maintain the values of these registers across the ISR. */
	sw			s6, 44(sp)
	sw			s5, 40(sp)
	sw			k1, portSTATUS_STACK_LOCATION(sp)

	/* Prepare to enable interrupts above the current priority. */
	srl			k0, k0, 0xa
	ins 		k1, k0, 10, 6
	ins			k1, zero, 1, 4

	/* s5 is used as the frame pointer. */
	add			s5, zero, sp

	/* Check the nesting count value. */
	la			k0, uxInterruptNesting
	lw			s6, (k0)

	/* If the nesting count is 0 then swap to the the system stack, otherwise
	the system stack is already being used. */
	bne			s6, zero, 1f
	nop

	/* Swap to the system stack. */
	la			sp, xISRStackTop
	lw			sp, (sp)

	/* Increment and save the nesting count. */
1:	addiu		s6, s6, 1
	sw			s6, 0(k0)

	/* s6 holds the EPC value, this is saved after interrupts are re-enabled. */
	mfc0 		s6, _CP0_EPC

	/* Re-enable interrupts. */
	mtc0		k1, _CP0_STATUS

	/* Save the context into the space just created.  s6 is saved again
	here as it now contains the EPC value.  No other s registers need be
	saved. */
	sw			ra, 120(s5)
	sw			s8, 116(s5)
	sw			t9, 112(s5)
	sw			t8, 108(s5)
	sw			t7, 104(s5)
	sw			t6, 100(s5)
	sw			t5, 96(s5)
	sw			t4, 92(s5)
	sw			t3, 88(s5)
	sw			t2, 84(s5)
	sw			t1, 80(s5)
	sw			t0, 76(s5)
	sw			a3, 72(s5)
	sw			a2, 68(s5)
	sw			a1, 64(s5)
	sw			a0, 60(s5)
	sw			v1, 56(s5)
	sw			v0, 52(s5)
	sw			s6, portEPC_STACK_LOCATION(s5)
	sw			$1, 16(s5)

	/* s6 is used as a scratch register. */
	mfhi		s6
	sw			s6, 12(s5)
	mflo		s6
	sw			s6, 8(s5)

	/* Update the task stack pointer value if nesting is zero. */
	la			s6, uxInterruptNesting
	lw			s6, (s6)
	addiu		s6, s6, -1
	bne			s6, zero, 1f
	nop

	/* Save the stack pointer. */
	la			s6, uxSavedTaskStackPointer
	sw			s5, (s6)
1:
	.endm

/******************************************************************/
.macro	portRESTORE_CONTEXT

	/* Restore the stack pointer from the TCB.  This is only done if the
	nesting count is 1. */
	la			s6, uxInterruptNesting
	lw			s6, (s6)
	addiu		s6, s6, -1
	bne			s6, zero, 1f
	nop
	la			s6, uxSavedTaskStackPointer
	lw			s5, (s6)

	/* Restore the context. */
1:	lw			s6, 8(s5)
	mtlo		s6
	lw			s6, 12(s5)
	mthi		s6
	lw			$1, 16(s5)
	/* s6 is loaded as it was used as a scratch register and therefore saved
	as part of the interrupt context. */
	lw			s6, 44(s5)
	lw			v0, 52(s5)
	lw			v1, 56(s5)
	lw			a0, 60(s5)
	lw			a1, 64(s5)
	lw			a2, 68(s5)
	lw			a3, 72(s5)
	lw			t0, 76(s5)
	lw			t1, 80(s5)
	lw			t2, 84(s5)
	lw			t3, 88(s5)
	lw			t4, 92(s5)
	lw			t5, 96(s5)
	lw			t6, 100(s5)
	lw			t7, 104(s5)
	lw			t8, 108(s5)
	lw			t9, 112(s5)
	lw			s8, 116(s5)
	lw			ra, 120(s5)

	/* Protect access to the k registers, and others. */
	di
	ehb

	/* Decrement the nesting count. */
	la			k0, uxInterruptNesting
	lw			k1, (k0)
	addiu		k1, k1, -1
	sw			k1, 0(k0)

	lw			k0, portSTATUS_STACK_LOCATION(s5)
	lw			k1, portEPC_STACK_LOCATION(s5)

	/* Leave the stack in its original state.  First load sp from s5, then
	restore s5 from the stack. */
	add			sp, zero, s5
	lw			s5, 40(sp)
	addiu		sp, sp,	portCONTEXT_SIZE

	mtc0		k0, _CP0_STATUS
	mtc0 		k1, _CP0_EPC
	ehb
	eret
	nop

	.endm