Subversion Repositories openrisc_2011-10-31

/*

    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.

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*/

/*

        Changes from V2.5.2

        + usCriticalNesting now has a volatile qualifier.

*/

/* Standard includes. */

#include <stdlib.h>

#include <signal.h>

/* Scheduler includes. */

#include "FreeRTOS.h"

#include "task.h"

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

 * Implementation of functions defined in portable.h for the MSP430 port.

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

/* Constants required for hardware setup.  The tick ISR runs off the ACLK,

not the MCLK. */

#define portACLK_FREQUENCY_HZ                   ( ( portTickType ) 32768 )

#define portINITIAL_CRITICAL_NESTING    ( ( unsigned short ) 10 )

#define portFLAGS_INT_ENABLED   ( ( portSTACK_TYPE ) 0x08 )

/* 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;

/* Most ports implement critical sections by placing the interrupt flags on

the stack before disabling interrupts.  Exiting the critical section is then

simply a case of popping the flags from the stack.  As mspgcc does not use

a frame pointer this cannot be done as modifying the stack will clobber all

the stack variables.  Instead each task maintains a count of the critical

section nesting depth.  Each time a critical section is entered the count is

incremented.  Each time a critical section is left the count is decremented -

with interrupts only being re-enabled if the count is zero.

usCriticalNesting will get set to zero when the scheduler starts, but must

not be initialised to zero as this will cause problems during the startup

sequence. */

volatile unsigned short usCriticalNesting = portINITIAL_CRITICAL_NESTING;

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

/*

 * Macro to save a task context to the task stack.  This simply pushes all the

 * general purpose msp430 registers onto the stack, followed by the

 * usCriticalNesting value used by the task.  Finally the resultant stack

 * pointer value is saved into the task control block so it can be retrieved

 * the next time the task executes.

 */

#define portSAVE_CONTEXT()                                                                      \

        asm volatile (  "push   r4                                              \n\t"   \

                                        "push   r5                                              \n\t"   \

                                        "push   r6                                              \n\t"   \

                                        "push   r7                                              \n\t"   \

                                        "push   r8                                              \n\t"   \

                                        "push   r9                                              \n\t"   \

                                        "push   r10                                             \n\t"   \

                                        "push   r11                                             \n\t"   \

                                        "push   r12                                             \n\t"   \

                                        "push   r13                                             \n\t"   \

                                        "push   r14                                             \n\t"   \

                                        "push   r15                                             \n\t"   \

                                        "mov.w  usCriticalNesting, r14  \n\t"   \

                                        "push   r14                                             \n\t"   \

                                        "mov.w  pxCurrentTCB, r12               \n\t"   \

                                        "mov.w  r1, @r12                                \n\t"   \

                                );

/*

 * Macro to restore a task context from the task stack.  This is effectively

 * the reverse of portSAVE_CONTEXT().  First the stack pointer value is

 * loaded from the task control block.  Next the value for usCriticalNesting

 * used by the task is retrieved from the stack - followed by the value of all

 * the general purpose msp430 registers.

 *

 * The bic instruction ensures there are no low power bits set in the status

 * register that is about to be popped from the stack.

 */

#define portRESTORE_CONTEXT()                                                           \

        asm volatile (  "mov.w  pxCurrentTCB, r12               \n\t"   \

                                        "mov.w  @r12, r1                                \n\t"   \

                                        "pop    r15                                             \n\t"   \

                                        "mov.w  r15, usCriticalNesting  \n\t"   \

                                        "pop    r15                                             \n\t"   \

                                        "pop    r14                                             \n\t"   \

                                        "pop    r13                                             \n\t"   \

                                        "pop    r12                                             \n\t"   \

                                        "pop    r11                                             \n\t"   \

                                        "pop    r10                                             \n\t"   \

                                        "pop    r9                                              \n\t"   \

                                        "pop    r8                                              \n\t"   \

                                        "pop    r7                                              \n\t"   \

                                        "pop    r6                                              \n\t"   \

                                        "pop    r5                                              \n\t"   \

                                        "pop    r4                                              \n\t"   \

                                        "bic    #(0xf0),0(r1)                   \n\t"   \

                                        "reti                                                   \n\t"   \

                                );

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

/*

 * Sets up the periodic ISR used for the RTOS tick.  This uses timer 0, but

 * could have alternatively used the watchdog timer or 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 and can be included if required.

                *pxTopOfStack = ( portSTACK_TYPE ) 0x1111;

                pxTopOfStack--;

                *pxTopOfStack = ( portSTACK_TYPE ) 0x2222;

                pxTopOfStack--;

                *pxTopOfStack = ( portSTACK_TYPE ) 0x3333;

                pxTopOfStack--;

        */

        /* The msp430 automatically pushes the PC then SR onto the stack before

        executing an ISR.  We want the stack to look just as if this has happened

        so place a pointer to the start of the task on the stack first - followed

        by the flags we want the task to use when it starts up. */

        *pxTopOfStack = ( portSTACK_TYPE ) pxCode;

        pxTopOfStack--;

        *pxTopOfStack = portFLAGS_INT_ENABLED;

        pxTopOfStack--;

        /* Next the general purpose registers. */

        *pxTopOfStack = ( portSTACK_TYPE ) 0x4444;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x5555;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x6666;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x7777;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x8888;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x9999;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xaaaa;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xbbbb;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xcccc;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xdddd;

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0xeeee;

        pxTopOfStack--;

        /* When the task starts is will expect to find the function parameter in

        R15. */

        *pxTopOfStack = ( portSTACK_TYPE ) pvParameters;

        pxTopOfStack--;

        /* The code generated by the mspgcc compiler does not maintain separate

        stack and frame pointers. The portENTER_CRITICAL macro cannot therefore

        use the stack as per other ports.  Instead a variable is used to keep

        track of the critical section nesting.  This variable has to be stored

        as part of the task context and is initially set to zero. */

        *pxTopOfStack = ( portSTACK_TYPE ) portNO_CRITICAL_SECTION_NESTING;

        /* Return a pointer to the top of the stack we have generated so this can

        be stored in the task control block for the task. */

        return pxTopOfStack;

}

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

portBASE_TYPE xPortStartScheduler( void )

{

        /* Setup the hardware to generate the tick.  Interrupts are disabled when

        this function is called. */

        prvSetupTimerInterrupt();

        /* Restore the context of the first task that is going to run. */

        portRESTORE_CONTEXT();

        /* Should not get here as the tasks are now running! */

        return pdTRUE;

}

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

void vPortEndScheduler( void )

{

        /* It is unlikely that the MSP430 port will get stopped.  If required simply

        disable the tick interrupt here. */

}

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

/*

 * Manual context switch called by portYIELD or taskYIELD.

 *

 * The first thing we do is save the registers so we can use a naked attribute.

 */

void vPortYield( void ) __attribute__ ( ( naked ) );

void vPortYield( void )

{

        /* We want the stack of the task being saved to look exactly as if the task

        was saved during a pre-emptive RTOS tick ISR.  Before calling an ISR the

        msp430 places the status register onto the stack.  As this is a function

        call and not an ISR we have to do this manually. */

        asm volatile ( "push    r2" );

        _DINT();

        /* Save the context of the current task. */

        portSAVE_CONTEXT();

        /* Switch to the highest priority task that is ready to run. */

        vTaskSwitchContext();

        /* Restore the context of the new task. */

        portRESTORE_CONTEXT();

}

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

/*

 * Hardware initialisation to generate the RTOS tick.  This uses timer 0

 * but could alternatively use the watchdog timer or timer 1.

 */

static void prvSetupTimerInterrupt( void )

{

        /* Ensure the timer is stopped. */

        TACTL = 0;

        /* Run the timer of the ACLK. */

        TACTL = TASSEL_1;

        /* Clear everything to start with. */

        TACTL |= TACLR;

        /* Set the compare match value according to the tick rate we want. */

        TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;

        /* Enable the interrupts. */

        TACCTL0 = CCIE;

        /* Start up clean. */

        TACTL |= TACLR;

        /* Up mode. */

        TACTL |= MC_1;

}

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

/*

 * The interrupt service routine used depends on whether the pre-emptive

 * scheduler is being used or not.

 */

#if configUSE_PREEMPTION == 1

        /*

         * Tick ISR for preemptive scheduler.  We can use a naked attribute as

         * the context is saved at the start of vPortYieldFromTick().  The tick

         * count is incremented after the context is saved.

         */

        interrupt (TIMERA0_VECTOR) prvTickISR( void ) __attribute__ ( ( naked ) );

        interrupt (TIMERA0_VECTOR) prvTickISR( void )

        {

                /* Save the context of the interrupted task. */

                portSAVE_CONTEXT();

                /* Increment the tick count then switch to the highest priority task

                that is ready to run. */

                vTaskIncrementTick();

                vTaskSwitchContext();

                /* Restore the context of the new task. */

                portRESTORE_CONTEXT();

        }

#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 (TIMERA0_VECTOR) prvTickISR( void );

        interrupt (TIMERA0_VECTOR) prvTickISR( void )

        {

                vTaskIncrementTick();

        }

#endif