port.c

FreeRTOS is a portable, open source, mini Real Time Kernel - a free to download and royalty free RTO

/*
	FreeRTOS.org V5.2.0 - Copyright (C) 2003-2009 Richard Barry.

	This file is part of the FreeRTOS.org distribution.

	FreeRTOS.org 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.

	FreeRTOS.org 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 along 
	with FreeRTOS.org; if not, write to the Free Software Foundation, Inc., 59 
	Temple Place, Suite 330, Boston, MA  02111-1307  USA.

	A special exception to the GPL is included to allow you to distribute a 
	combined work that includes FreeRTOS.org without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details.


	***************************************************************************
	*                                                                         *
	* Get the FreeRTOS eBook!  See http://www.FreeRTOS.org/Documentation      *
	*                                                                         *
	* This is a concise, step by step, 'hands on' guide that describes both   *
	* general multitasking concepts and FreeRTOS specifics. It presents and   *
	* explains numerous examples that are written using the FreeRTOS API.     *
	* Full source code for all the examples is provided in an accompanying    *
	* .zip file.                                                              *
	*                                                                         *
	***************************************************************************

	1 tab == 4 spaces!

	Please ensure to read the configuration and relevant port sections of the
	online documentation.

	http://www.FreeRTOS.org - Documentation, latest information, license and
	contact details.

	http://www.SafeRTOS.com - A version that is certified for use in safety
	critical systems.

	http://www.OpenRTOS.com - Commercial support, development, porting,
	licensing and training services.
*/

#include "FreeRTOS.h"
#include "task.h"
#include "mb91467d.h"

/*-----------------------------------------------------------*/

/* We require the address of the pxCurrentTCB variable, but don't want to know
any details of its type. */
typedef void tskTCB;
extern volatile tskTCB * volatile pxCurrentTCB;

/*-----------------------------------------------------------*/
 
#pragma asm
#macro  SaveContext
	 ORCCR #0x20								;Switch to user stack
	 ST RP,@-R15								;Store RP
	 STM0 (R7,R6,R5,R4,R3,R2,R1,R0)				;Store R7-R0
	 STM1 (R14,R13,R12,R11,R10,R9,R8)			;Store R14-R8
	 ST MDH, @-R15								;Store MDH
	 ST MDL, @-R15								;Store MDL
	 
	 ANDCCR #0xDF								;Switch back to system stack
	 LD @R15+,R0								;Store PC to R0 
	 ORCCR #0x20								;Switch to user stack
	 ST R0,@-R15								;Store PC to User stack
	 
	 ANDCCR #0xDF								;Switch back to system stack
	 LD @R15+,R0								;Store PS to R0
	 ORCCR #0x20								;Switch to user stack
	 ST R0,@-R15								;Store PS to User stack
	 
	 LDI #_pxCurrentTCB, R0						;Get pxCurrentTCB address
	 LD @R0, R0									;Get the pxCurrentTCB->pxTopOfStack address
	 ST R15,@R0									;Store USP to pxCurrentTCB->pxTopOfStack
	 
	 ANDCCR #0xDF								;Switch back to system stack for the rest of tick ISR
#endm

#macro RestoreContext
	 LDI #_pxCurrentTCB, R0						;Get pxCurrentTCB address
	 LD @R0, R0									;Get the pxCurrentTCB->pxTopOfStack address
	 ORCCR #0x20								;Switch to user stack
	 LD @R0, R15								;Restore USP from pxCurrentTCB->pxTopOfStack

	 LD @R15+,R0								;Store PS to R0
	 ANDCCR #0xDF								;Switch to system stack
	 ST R0,@-R15								;Store PS to system stack

	 ORCCR #0x20								;Switch to user stack
	 LD @R15+,R0								;Store PC to R0
	 ANDCCR #0xDF								;Switch to system stack
	 ST R0,@-R15								;Store PC to system stack

	 ORCCR #0x20								;Switch back to retrieve the remaining context

	 LD @R15+, MDL								;Restore MDL
	 LD @R15+, MDH								;Restore MDH
	 LDM1 (R14,R13,R12,R11,R10,R9,R8)			;Restore R14-R8
	 LDM0 (R7,R6,R5,R4,R3,R2,R1,R0)				;Restore R7-R0
	 LD @R15+, RP								;Restore RP
	 
	 ANDCCR #0xDF								;Switch back to system stack for the rest of tick ISR
#endm
#pragma endasm

/*-----------------------------------------------------------*/

/*
 * Perform hardware setup to enable ticks from timer 1,
 */
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/

/* 
 * Initialise the stack of a task to look exactly as if a call to 
 * portSAVE_CONTEXT had been called.
 * 
 * See the header file portable.h.
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
	/* Place a few bytes of known values on the bottom of the stack. 
	This is just useful for debugging. */

	*pxTopOfStack = 0x11111111;
	pxTopOfStack--;
	*pxTopOfStack = 0x22222222;
	pxTopOfStack--;
	*pxTopOfStack = 0x33333333;
	pxTopOfStack--;

	/* This is a redundant push to the stack, it may be required if 
	in some implementations of the compiler the parameter to the task 
	is passed on to the stack rather than in R4 register. */
	*pxTopOfStack = (portSTACK_TYPE)(pvParameters);
	pxTopOfStack--;                  
    
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00000000;	/* RP */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00007777;	/* R7 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00006666;	/* R6 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00005555;	/* R5 */
	pxTopOfStack--;
	
	/* In the current implementation of the compiler the first 
	parameter to the task (or function) is passed via R4 parameter 
	to the task, hence the pvParameters pointer is copied into the R4 
	register. See compiler manual section 4.6.2 for more information. */
	*pxTopOfStack = ( portSTACK_TYPE ) (pvParameters);	/* R4 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00003333;	/* R3 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00002222;	/* R2 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00001111;	/* R1 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00000001;	/* R0 */
	pxTopOfStack--;	
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0000EEEE;	/* R14 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0000DDDD;	/* R13 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0000CCCC;	/* R12 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0000BBBB;	/* R11 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x0000AAAA;	/* R10 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00009999;	/* R9 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00008888;	/* R8 */
	pxTopOfStack--;	
	*pxTopOfStack = ( portSTACK_TYPE ) 0x11110000;	/* MDH */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x22220000;	/* MDL */
	pxTopOfStack--;

	/* The start of the task code. */
	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
	pxTopOfStack--;
	 
    /* PS - User Mode, USP, ILM=31, Interrupts enabled */
	*pxTopOfStack = ( portSTACK_TYPE ) 0x001F0030;	/* PS */

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
	/* Setup the hardware to generate the tick. */
	prvSetupTimerInterrupt();

	/* Restore the context of the first task that is going to run. */
	#pragma asm
		RestoreContext
	#pragma endasm

	/* Simulate a function call end as generated by the compiler.  We will now
	jump to the start of the task the context of which we have just restored. */	
	__asm(" reti ");

	/* Should not get here. */
	return pdFAIL;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented - unlikely to ever be required as there is nothing to
	return to. */
}
/*-----------------------------------------------------------*/

static void prvSetupTimerInterrupt( void )
{
/* The peripheral clock divided by 32 is used by the timer. */
const unsigned portSHORT usReloadValue = ( unsigned portSHORT ) ( ( ( configPER_CLOCK_HZ / configTICK_RATE_HZ ) / 32UL ) - 1UL );

	/* Setup RLT0 to generate a tick interrupt. */

	TMCSR0_CNTE = 0;		/* Count Disable */
    TMCSR0_CSL = 0x2;		/* CLKP/32 */
    TMCSR0_MOD = 0;			/* Software trigger */
    TMCSR0_RELD = 1;		/* Reload */
    
    TMCSR0_UF = 0;			/* Clear underflow flag */
	TMRLR0 = usReloadValue;
	TMCSR0_INTE = 1;		/* Interrupt Enable */
	TMCSR0_CNTE = 1;		/* Count Enable */
	TMCSR0_TRG = 1;			/* Trigger */
	
    PORTEN = 0x3;			/* Port Enable */
}
/*-----------------------------------------------------------*/

#if configUSE_PREEMPTION == 1

	/* 
	 * Tick ISR for preemptive scheduler. The tick count is incremented 
	 * after the context is saved. Then the context is switched if required,
	 * and last the context of the task which is to be resumed is restored.
	 */

	#pragma asm

	.global _ReloadTimer0_IRQHandler
	_ReloadTimer0_IRQHandler:

	ANDCCR #0xEF							;Disable Interrupts
	SaveContext								;Save context
	ORCCR #0x10								;Re-enable Interrupts

	LDI #0xFFFB,R1
	LDI #_tmcsr0, R0
	AND R1,@R0								;Clear RLT0 interrupt flag

	CALL32	 _vTaskIncrementTick,R12		;Increment Tick
	CALL32	 _vTaskSwitchContext,R12		;Switch context if required

	ANDCCR #0xEF							;Disable Interrupts
	RestoreContext							;Restore context
	ORCCR #0x10								;Re-enable Interrupts

	RETI

	#pragma endasm
	
#else
	
	/* 
	 * Tick ISR for the cooperative scheduler.  All this does is increment the
	 * tick count.  We don't need to switch context, this can only be done by
	 * manual calls to taskYIELD();
	 */
	__interrupt void ReloadTimer0_IRQHandler( void )
	{
		/* Clear RLT0 interrupt flag */
		TMCSR0_UF = 0; 
		vTaskIncrementTick();
	}

#endif

/*
 * Manual context switch. We can use a __nosavereg attribute  as the context 
 * would be saved by PortSAVE_CONTEXT().  The context is switched and then 
 * the context of the new task is restored saved. 
 */
#pragma asm

	.global _vPortYieldDelayed
	_vPortYieldDelayed:

	ANDCCR #0xEF							;Disable Interrupts
	SaveContext								;Save context
	ORCCR #0x10								;Re-enable Interrupts

	LDI #_dicr, R0
	BANDL #0x0E, @R0						;Clear Delayed interrupt flag

	CALL32	 _vTaskSwitchContext,R12		;Switch context if required

	ANDCCR #0xEF							;Disable Interrupts
	RestoreContext							;Restore context
	ORCCR #0x10								;Re-enable Interrupts

	RETI

#pragma endasm
/*-----------------------------------------------------------*/

/*
 * Manual context switch. We can use a __nosavereg attribute  as the context 
 * would be saved by PortSAVE_CONTEXT().  The context is switched and then 
 * the context of the new task is restored saved. 
 */ 	 
#pragma asm

	.global _vPortYield
	_vPortYield:

	SaveContext								;Save context
	CALL32	 _vTaskSwitchContext,R12		;Switch context if required
	RestoreContext							;Restore context
	
	RETI

#pragma endasm
/*-----------------------------------------------------------*/