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/*
    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
 
    ***************************************************************************
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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 exception 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.  See the GNU General Public License for
    more details. You should have received a copy of the GNU General Public 
    License and the FreeRTOS license exception along with FreeRTOS; if not it 
    can be viewed here: http://www.freertos.org/a00114.html and also obtained 
    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.
 
    1 tab == 4 spaces!
 
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*/
 
/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the OpenRISC port.
 *----------------------------------------------------------*/
 
 
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
 
/* Processor constants. */
#include "port_spr_defs.h"
 
/* Jump buffer */
#include <setjmp.h>
static jmp_buf jmpbuf;
 
/* Tick Timer Interrupt handler */
void vTickHandler( void );	
 
/* Setup the timer to generate the tick interrupts. */
static void prvSetupTimerInterrupt( void );
 
/* For writing into SPR. */
static inline void mtspr(unsigned long spr, unsigned long value) 
{	
	asm("l.mtspr\t\t%0,%1,0": : "r" (spr), "r" (value));
}
 
/* For reading SPR. */
static inline unsigned long mfspr(unsigned long spr) 
{	
	unsigned long value;
	asm("l.mfspr\t\t%0,%1,0" : "=r" (value) : "r" (spr));
	return value;
}
 
/* forward decleation */
inline void vPortDisableInterrupts( void );
inline void vPortEnableInterrupts( void );
 
/* 
 * Initialise the stack of a task to look exactly as if a call to 
 * portSAVE_CONTEXT had been called. Context layout is described in
 * portmarco.h
 *
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
	unsigned portLONG uTaskSR = mfspr(SPR_SR);			
	uTaskSR |= SPR_SR_SM;						// Supervisor mode
	uTaskSR |= (SPR_SR_TEE | SPR_SR_IEE);		// Tick interrupt enable, All External interupt enable
 
	// allocate redzone	
	pxTopOfStack -= REDZONE_SIZE/4;			
 
	/* Setup the initial stack of the task.  The stack is set exactly as 
	expected by the portRESTORE_CONTEXT() macro. */
	*(--pxTopOfStack) = (portSTACK_TYPE)pxCode;			// SPR_EPCR_BASE(0)
	*(--pxTopOfStack) = (portSTACK_TYPE)uTaskSR;		// SPR_ESR_BASE(0) 
 
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000031;		// r31
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000030;		// r30
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000029;		// r29
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000028;		// r28
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000027;		// r27
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000026;		// r26
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000025;		// r25
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000024;		// r24
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000023;		// r23
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000022;		// r22
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000021;		// r21
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000020;		// r20
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000019;		// r19
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000018;		// r18
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000017;		// r17
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000016;		// r16
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000015;		// r15
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000014;		// r14
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000013;		// r13
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000012;		// r12
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000011;		// r11
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000010;		// r10
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000008;		// r8
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000007;		// r7
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000006;		// r6
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000005;		// r5
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000004;		// r4
	*(--pxTopOfStack) = (portSTACK_TYPE)pvParameters;	// task argument
	*(--pxTopOfStack) = (portSTACK_TYPE)0x00000002;		// r2
	*(--pxTopOfStack) = (portSTACK_TYPE)pxCode;			// PC
 
	return pxTopOfStack;
}
 
portBASE_TYPE xPortStartScheduler( void )
{
	if(setjmp((void *)jmpbuf) == 0) {
		/* Start the timer that generates the tick ISR.  Interrupts are disabled
		here already. */
		prvSetupTimerInterrupt();
 
		/* Start the first task. */
		asm volatile (                              
		" .global	pxCurrentTCB	\n\t"
		/*   restore stack pointer         	*/
		"   l.movhi	r3, hi(pxCurrentTCB)		\n\t"
		"   l.ori	r3, r3, lo(pxCurrentTCB)	\n\t"
		"   l.lwz	r3, 0x0(r3)		\n\t"
		"   l.lwz	r1, 0x0(r3)		\n\t"
		/*   restore context               	*/
		"   l.lwz	r9,  0x00(r1)	\n\t"
		"   l.lwz	r2,  0x04(r1)	\n\t"
		"   l.lwz	r6,  0x14(r1)	\n\t"
		"   l.lwz	r7,  0x18(r1)	\n\t"
		"   l.lwz	r8,  0x1C(r1)	\n\t"
		"   l.lwz	r10, 0x20(r1)	\n\t"
		"   l.lwz	r11, 0x24(r1)	\n\t"
		"   l.lwz	r12, 0x28(r1)	\n\t"
		"   l.lwz	r13, 0x2C(r1)	\n\t"
		"   l.lwz	r14, 0x30(r1)	\n\t"
		"   l.lwz	r15, 0x34(r1)	\n\t"
		"   l.lwz	r16, 0x38(r1)	\n\t"
		"   l.lwz	r17, 0x3C(r1)	\n\t"
		"   l.lwz	r18, 0x40(r1)	\n\t"
		"   l.lwz	r19, 0x44(r1)	\n\t"
		"   l.lwz	r20, 0x48(r1)	\n\t"
		"   l.lwz	r21, 0x4C(r1)	\n\t"
		"   l.lwz	r22, 0x50(r1)	\n\t"
		"   l.lwz	r23, 0x54(r1)	\n\t"
		"   l.lwz	r24, 0x58(r1)	\n\t"
		"   l.lwz	r25, 0x5C(r1)	\n\t"
		"   l.lwz	r26, 0x60(r1)	\n\t"
		"   l.lwz	r27, 0x64(r1)	\n\t"
		"   l.lwz	r28, 0x68(r1)	\n\t"
		"   l.lwz	r29, 0x6C(r1)	\n\t"
		"   l.lwz	r30, 0x70(r1)	\n\t"
		"   l.lwz	r31, 0x74(r1)	\n\t"
		/*  restore SPR_ESR_BASE(0), SPR_EPCR_BASE(0) */
		"   l.lwz	r3,  0x78(r1)	\n\t"
		"   l.lwz	r4,  0x7C(r1)	\n\t"
		"   l.mtspr	r0,  r3, %1	 	\n\t"
		"   l.mtspr	r0,  r4, %2	 	\n\t"
		/*   restore clobber register     */
		"   l.lwz	r3,  0x08(r1)	\n\t"
		"   l.lwz	r4,  0x0C(r1)	\n\t"
		"   l.lwz	r5,  0x10(r1)	\n\t"
		"   l.addi	r1,  r1, %0	 	\n\t"
		"   l.rfe                	\n\t"
		"   l.nop                	\n\t"
		:
		: 	"n"(STACKFRAME_SIZE), 
			"n"(SPR_ESR_BASE), 
			"n"(SPR_EPCR_BASE)
		);
 
		/* Should not get here! */
	} else {
		/* Retrun by vPortEndScheduler */
	}
 
	return 0;
}
 
void vPortEndScheduler( void )
{
	mtspr(SPR_SR, mfspr(SPR_SR) & (~SPR_SR_TEE));	// Tick stop
	longjmp((void *)jmpbuf, 1);						// return to xPortStartScheduler
}
 
/*
 * Setup the tick timer to generate the tick interrupts at the required frequency.
 */
static void prvSetupTimerInterrupt( void )
{
	const unsigned portLONG ulTickPeriod = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
 
	// Disable tick timer exception recognition 
	mtspr(SPR_SR, mfspr(SPR_SR) & ~SPR_SR_TEE);
 
	// clears interrupt
   	mtspr(SPR_TTMR, mfspr(SPR_TTMR) & ~(SPR_TTMR_IP)); 
 
	// Set period of one cycle, restartable mode 
	mtspr(SPR_TTMR, SPR_TTMR_IE | SPR_TTMR_RT | (ulTickPeriod & SPR_TTMR_PERIOD));
 
	// Reset counter 
	mtspr(SPR_TTCR, 0);
 
    // set OR1200 to accept exceptions
    mtspr(SPR_SR, mfspr(SPR_SR) | SPR_SR_TEE);
}
 
inline void vPortDisableInterrupts( void ) 
{
	mtspr(SPR_SR, mfspr(SPR_SR) & ~(SPR_SR_TEE|SPR_SR_IEE));	// Tick, interrupt stop
}
 
inline void vPortEnableInterrupts( void )
{
	mtspr(SPR_SR, mfspr(SPR_SR) | (SPR_SR_TEE|SPR_SR_IEE));		// Tick, interrupt start
}
 
/* 
 * naked attribute is ignored or32-elf-gcc 4.5.1-or32-1.0rc1 
 * use assemble routines in portasm.S
 */
#if 0
void vTickHandler( void )
{
	// clears interrupt
	mtspr(SPR_TTMR, mfspr(SPR_TTMR) & ~(SPR_TTMR_IP));    
 
	/* Increment the RTOS tick count, then look for the highest priority 
	   task that is ready to run. */
	vTaskIncrementTick();
 
	// The cooperative scheduler requires a normal simple Tick ISR to
	// simply increment the system tick.
#if configUSE_PREEMPTION == 0
	// nothing to do here
#else
	/* Save the context of the current task. */
	portSAVE_CONTEXT();			
 
	/* Find the highest priority task that is ready to run. */
	vTaskSwitchContext();
 
	portRESTORE_CONTEXT();
#endif
}
#endif