/*
 * 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
 *
 */

#include "FreeRTOSConfig.h"

	.extern pxCurrentTCB
	.extern vTaskSwitchContext
	.extern xTaskIncrementTick
	.extern vPortISRHandler

	.global vPortStartFirstTask
	.global vPortYield
	.global vPortTickISR
	.global vPortISRWrapper
	.global vPortSaveFPURegisters
	.global vPortRestoreFPURegisters

.set	BChainField, 0
.set	NextLRField, BChainField + 4
.set	MSRField,    NextLRField + 4
.set	PCField,     MSRField    + 4
.set	LRField,     PCField     + 4
.set	CTRField,    LRField     + 4
.set	XERField,    CTRField    + 4
.set	CRField,     XERField    + 4
.set	USPRG0Field, CRField     + 4
.set	r0Field,     USPRG0Field + 4
.set	r2Field,     r0Field     + 4
.set	r3r31Field,  r2Field     + 4
.set	IFrameSize,  r3r31Field  + ( ( 31 - 3 ) + 1 ) * 4


.macro portSAVE_STACK_POINTER_AND_LR

	/* Get the address of the TCB. */
	xor		R0, R0, R0
	addis	R2, R0, pxCurrentTCB@ha
	lwz		R2,	pxCurrentTCB@l( R2 )

	/* Store the stack pointer into the TCB */
	stw		SP,	0( R2 )

	/* Save the link register */
	stwu	R1, -24( R1 )
	mflr	R0
	stw		R31, 20( R1 )
	stw		R0, 28( R1 )
	mr		R31, r1

.endm

.macro portRESTORE_STACK_POINTER_AND_LR

	/* Restore the link register */
	lwz		R11, 0( R1 )
	lwz		R0, 4( R11 )
	mtlr	R0
	lwz		R31, -4( R11 )
	mr		R1, R11

	/* Get the address of the TCB. */
	xor		R0, R0, R0
	addis   SP, R0, pxCurrentTCB@ha
	lwz		SP,	pxCurrentTCB@l( R1 )

	/* Get the task stack pointer from the TCB. */
	lwz		SP, 0( SP )

.endm


vPortStartFirstTask:

	/* Get the address of the TCB. */
	xor		R0, R0, R0
    addis   SP, R0, pxCurrentTCB@ha
    lwz		SP,	pxCurrentTCB@l( SP )

	/* Get the task stack pointer from the TCB. */
	lwz		SP, 0( SP )
	
	/* Restore MSR register to SRR1. */
	lwz		R0, MSRField(R1)
	mtsrr1	R0
	
	/* Restore current PC location to SRR0. */
	lwz		R0, PCField(R1)
	mtsrr0	R0

	/* Save  USPRG0 register */
	lwz		R0, USPRG0Field(R1)
	mtspr	0x100,R0
	
	/* Restore Condition register */
	lwz		R0, CRField(R1)
	mtcr	R0
	
	/* Restore Fixed Point Exception register */
	lwz		R0, XERField(R1)
	mtxer	R0
	
	/* Restore Counter register */
	lwz		R0, CTRField(R1)
	mtctr	R0
	
	/* Restore Link register */
	lwz		R0, LRField(R1)
	mtlr	R0
	
	/* Restore remaining GPR registers. */
	lmw	R3,r3r31Field(R1)
	
	/* Restore r0 and r2. */
	lwz		R0, r0Field(R1)
	lwz		R2, r2Field(R1)
	
	/* Remove frame from stack */
	addi	R1,R1,IFrameSize

	/* Return into the first task */
	rfi



vPortYield:

	portSAVE_STACK_POINTER_AND_LR
	bl vTaskSwitchContext
	portRESTORE_STACK_POINTER_AND_LR
	blr

vPortTickISR:

	portSAVE_STACK_POINTER_AND_LR
	bl xTaskIncrementTick
	
	#if configUSE_PREEMPTION == 1
		bl vTaskSwitchContext
	#endif

	/* Clear the interrupt */
	lis		R0, 2048
	mttsr	R0

	portRESTORE_STACK_POINTER_AND_LR
	blr

vPortISRWrapper:

	portSAVE_STACK_POINTER_AND_LR
	bl vPortISRHandler
	portRESTORE_STACK_POINTER_AND_LR
	blr

#if configUSE_FPU == 1

vPortSaveFPURegisters:

	/* Enable APU and mark FPU as present. */
	mfmsr	r0
	xor		r30, r30, r30
	oris	r30, r30, 512
	ori		r30, r30, 8192
	or		r0, r0, r30
	mtmsr	r0

#ifdef USE_DP_FPU

	/* Buffer address is in r3.  Save each flop register into an offset from
	this buffer address. */
	stfd	f0, 0(r3)
	stfd	f1, 8(r3)
	stfd	f2, 16(r3)
	stfd	f3, 24(r3)
	stfd	f4, 32(r3)
	stfd	f5, 40(r3)
	stfd	f6, 48(r3)
	stfd	f7, 56(r3)
	stfd	f8, 64(r3)
	stfd	f9, 72(r3)
	stfd	f10, 80(r3)
	stfd	f11, 88(r3)
	stfd	f12, 96(r3)
	stfd	f13, 104(r3)
	stfd	f14, 112(r3)
	stfd	f15, 120(r3)
	stfd	f16, 128(r3)
	stfd	f17, 136(r3)
	stfd	f18, 144(r3)
	stfd	f19, 152(r3)
	stfd	f20, 160(r3)
	stfd	f21, 168(r3)
	stfd	f22, 176(r3)
	stfd	f23, 184(r3)
	stfd	f24, 192(r3)
	stfd	f25, 200(r3)
	stfd	f26, 208(r3)
	stfd	f27, 216(r3)
	stfd	f28, 224(r3)
	stfd	f29, 232(r3)
	stfd	f30, 240(r3)
	stfd	f31, 248(r3)	
	
	/* Also save the FPSCR. */
	mffs	f31
	stfs	f31, 256(r3)

#else

	/* Buffer address is in r3.  Save each flop register into an offset from
	this buffer address. */
	stfs	f0, 0(r3)
	stfs	f1, 4(r3)
	stfs	f2, 8(r3)
	stfs	f3, 12(r3)
	stfs	f4, 16(r3)
	stfs	f5, 20(r3)
	stfs	f6, 24(r3)
	stfs	f7, 28(r3)
	stfs	f8, 32(r3)
	stfs	f9, 36(r3)
	stfs	f10, 40(r3)
	stfs	f11, 44(r3)
	stfs	f12, 48(r3)
	stfs	f13, 52(r3)
	stfs	f14, 56(r3)
	stfs	f15, 60(r3)
	stfs	f16, 64(r3)
	stfs	f17, 68(r3)
	stfs	f18, 72(r3)
	stfs	f19, 76(r3)
	stfs	f20, 80(r3)
	stfs	f21, 84(r3)
	stfs	f22, 88(r3)
	stfs	f23, 92(r3)
	stfs	f24, 96(r3)
	stfs	f25, 100(r3)
	stfs	f26, 104(r3)
	stfs	f27, 108(r3)
	stfs	f28, 112(r3)
	stfs	f29, 116(r3)
	stfs	f30, 120(r3)
	stfs	f31, 124(r3)
	
	/* Also save the FPSCR. */
	mffs	f31
	stfs	f31, 128(r3)
	
#endif

	blr

#endif /* configUSE_FPU. */


#if configUSE_FPU == 1

vPortRestoreFPURegisters:

	/* Enable APU and mark FPU as present. */
	mfmsr	r0
	xor		r30, r30, r30
	oris	r30, r30, 512
	ori		r30, r30, 8192
	or		r0, r0, r30
	mtmsr	r0

#ifdef USE_DP_FPU

	/* Buffer address is in r3.  Restore each flop register from an offset
	into this buffer. 
	
	First the FPSCR. */
	lfs		f31, 256(r3)
	mtfsf	f31, 7

	lfd		f0, 0(r3)
	lfd	    f1, 8(r3)
	lfd		f2, 16(r3)
	lfd		f3, 24(r3)
	lfd		f4, 32(r3)
	lfd		f5, 40(r3)
	lfd		f6, 48(r3)
	lfd		f7, 56(r3)
	lfd		f8, 64(r3)
	lfd		f9, 72(r3)
	lfd		f10, 80(r3)
	lfd		f11, 88(r3)
	lfd		f12, 96(r3)
	lfd		f13, 104(r3)
	lfd		f14, 112(r3)
	lfd		f15, 120(r3)
	lfd		f16, 128(r3)
	lfd		f17, 136(r3)
	lfd		f18, 144(r3)
	lfd		f19, 152(r3)
	lfd		f20, 160(r3)
	lfd		f21, 168(r3)
	lfd		f22, 176(r3)
	lfd		f23, 184(r3)
	lfd		f24, 192(r3)
	lfd		f25, 200(r3)
	lfd		f26, 208(r3)
	lfd		f27, 216(r3)
	lfd		f28, 224(r3)
	lfd		f29, 232(r3)
	lfd		f30, 240(r3)
	lfd		f31, 248(r3)

#else

	/* Buffer address is in r3.  Restore each flop register from an offset
	into this buffer. 
	
	First the FPSCR. */
	lfs		f31, 128(r3)
	mtfsf	f31, 7

	lfs		f0, 0(r3)
	lfs		f1, 4(r3)
	lfs		f2, 8(r3)
	lfs		f3, 12(r3)
	lfs		f4, 16(r3)
	lfs		f5, 20(r3)
	lfs		f6, 24(r3)
	lfs		f7, 28(r3)
	lfs		f8, 32(r3)
	lfs		f9, 36(r3)
	lfs		f10, 40(r3)
	lfs		f11, 44(r3)
	lfs		f12, 48(r3)
	lfs		f13, 52(r3)
	lfs		f14, 56(r3)
	lfs		f15, 60(r3)
	lfs		f16, 64(r3)
	lfs		f17, 68(r3)
	lfs		f18, 72(r3)
	lfs		f19, 76(r3)
	lfs		f20, 80(r3)
	lfs		f21, 84(r3)
	lfs		f22, 88(r3)
	lfs		f23, 92(r3)
	lfs		f24, 96(r3)
	lfs		f25, 100(r3)
	lfs		f26, 104(r3)
	lfs		f27, 108(r3)
	lfs		f28, 112(r3)
	lfs		f29, 116(r3)
	lfs		f30, 120(r3)
	lfs		f31, 124(r3)

#endif

	blr

#endif /* configUSE_FPU. */