/*
 * FreeRTOS Kernel <DEVELOPMENT BRANCH>
 * Copyright (C) 2021 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.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 * 1 tab == 4 spaces!
 */

.file "portASM.S"
#include "FreeRTOSConfig.h"
#include "ISR_Support.h"

	.extern pxCurrentTCB
	.extern vTaskSwitchContext
	.extern vPortCentralInterruptHandler
	.extern xTaskIncrementTick
	.extern vPortAPICErrorHandler
	.extern pucPortTaskFPUContextBuffer
	.extern ulPortYieldPending

	.global vPortStartFirstTask
	.global vPortCentralInterruptWrapper
	.global vPortAPICErrorHandlerWrapper
	.global vPortTimerHandler
	.global vPortYieldCall
	.global vPortAPICSpuriousHandler

	.text

/*-----------------------------------------------------------*/

.align 4
.func vPortYieldCall
vPortYieldCall:
	/* Save general purpose registers. */
	pusha

	.if configSUPPORT_FPU == 1

		/* If the task has a buffer allocated to save the FPU context then save
		the FPU context now. */
		movl	pucPortTaskFPUContextBuffer, %eax
		test	%eax, %eax
		je		1f
		fnsave	( %eax )
		fwait

		1:

		/* Save the address of the FPU context, if any. */
		push	pucPortTaskFPUContextBuffer

	.endif /* configSUPPORT_FPU */

	/* Find the TCB. */
	movl 	pxCurrentTCB, %eax

	/* Stack location is first item in the TCB. */
	movl	%esp, (%eax)

	call vTaskSwitchContext

	/* Find the location of pxCurrentTCB again - a callee saved register could
	be used in place of eax to prevent this second load, but that then relies
	on the compiler and other asm code. */
	movl 	pxCurrentTCB, %eax
	movl	(%eax), %esp

	.if configSUPPORT_FPU == 1

		/* Restore address of task's FPU context buffer. */
		pop 	pucPortTaskFPUContextBuffer

		/* If the task has a buffer allocated in which its FPU context is saved,
		then restore it now. */
		movl	pucPortTaskFPUContextBuffer, %eax
		test	%eax, %eax
		je		1f
		frstor	( %eax )
		1:
	.endif

	popa
	iret

.endfunc
/*-----------------------------------------------------------*/

.align 4
.func vPortStartFirstTask
vPortStartFirstTask:

	/* Find the TCB. */
	movl 	pxCurrentTCB, %eax

	/* Stack location is first item in the TCB. */
	movl	(%eax), %esp

	/* Restore FPU context flag. */
	.if configSUPPORT_FPU == 1

		pop 	pucPortTaskFPUContextBuffer

	.endif /* configSUPPORT_FPU */

	/* Restore general purpose registers. */
	popa
	iret
.endfunc
/*-----------------------------------------------------------*/

.align 4
.func vPortAPICErrorHandlerWrapper
vPortAPICErrorHandlerWrapper:
	pusha
	call	vPortAPICErrorHandler
	popa
	/* EOI. */
	movl	$0x00, (0xFEE000B0)
	iret
.endfunc
/*-----------------------------------------------------------*/

.align 4
.func vPortTimerHandler
vPortTimerHandler:

	/* Save general purpose registers. */
	pusha

	/* Interrupts are not nested, so save the rest of the task context. */
	.if configSUPPORT_FPU == 1

		/* If the task has a buffer allocated to save the FPU context then save the
		FPU context now. */
		movl	pucPortTaskFPUContextBuffer, %eax
		test	%eax, %eax
		je		1f
		fnsave	( %eax ) /* Save FLOP context into ucTempFPUBuffer array. */
		fwait

		1:
		/* Save the address of the FPU context, if any. */
		push	pucPortTaskFPUContextBuffer

	.endif /* configSUPPORT_FPU */

	/* Find the TCB. */
	movl 	pxCurrentTCB, %eax

	/* Stack location is first item in the TCB. */
	movl	%esp, (%eax)

	/* Switch stacks. */
	movl 	ulTopOfSystemStack, %esp
	movl	%esp, %ebp

	/* Increment nesting count. */
	add 	$1, ulInterruptNesting

	call 	xTaskIncrementTick

	sti

	/* Is a switch to another task required? */
	test	%eax, %eax
	je		_skip_context_switch
	cli
	call	vTaskSwitchContext

_skip_context_switch:
	cli

	/* Decrement the variable used to determine if a switch to a system
	stack is necessary. */
	sub		$1, ulInterruptNesting

	/* Stack location is first item in the TCB. */
	movl 	pxCurrentTCB, %eax
	movl	(%eax), %esp

	.if configSUPPORT_FPU == 1

		/* Restore address of task's FPU context buffer. */
		pop 	pucPortTaskFPUContextBuffer

		/* If the task has a buffer allocated in which its FPU context is saved,
		then restore it now. */
		movl	pucPortTaskFPUContextBuffer, %eax
		test	%eax, %eax
		je		1f
		frstor	( %eax )
		1:
	.endif

	popa

	/* EOI. */
	movl	$0x00, (0xFEE000B0)
	iret

.endfunc
/*-----------------------------------------------------------*/

.if configUSE_COMMON_INTERRUPT_ENTRY_POINT == 1

	.align 4
	.func vPortCentralInterruptWrapper
	vPortCentralInterruptWrapper:

		portFREERTOS_INTERRUPT_ENTRY

		movl $0xFEE00170, %eax 			/* Highest In Service Register (ISR) long word. */
		movl $8, %ecx					/* Loop counter. */

	next_isr_long_word:
		test %ecx, %ecx					/* Loop counter reached 0? */
		je wrapper_epilogue				/* Looked at all ISR registers without finding a bit set. */
		sub $1, %ecx					/* Sub 1 from loop counter. */
		movl (%eax), %ebx				/* Load next ISR long word. */
		sub $0x10, %eax					/* Point to next ISR long word in case no bits are set in the current long word. */
		test %ebx, %ebx					/* Are there any bits set? */
		je next_isr_long_word			/* Look at next ISR long word if no bits were set. */
		sti
		bsr %ebx, %ebx					/* A bit was set, which one? */
		movl $32, %eax					/* Destination operand for following multiplication. */
		mul %ecx						/* Calculate base vector for current register, 32 vectors per register. */
		add %ebx, %eax					/* Add bit offset into register to get final vector number. */
		push %eax						/* Vector number is function parameter. */
		call vPortCentralInterruptHandler
		pop %eax						/* Remove parameter. */

	wrapper_epilogue:
		portFREERTOS_INTERRUPT_EXIT

	.endfunc

.endif /* configUSE_COMMON_INTERRUPT_ENTRY_POINT */
/*-----------------------------------------------------------*/

.align 4
.func vPortAPISpuriousHandler
vPortAPICSpuriousHandler:
	iret

.endfunc

.end