XCC/Xtensa/port.c

/*
 * FreeRTOS Kernel V10.6.2
 * Copyright (C) 2015-2019 Cadence Design Systems, Inc.
 * 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 <stdlib.h>
#include <xtensa/config/core.h>

#include "xtensa_rtos.h"

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


/* Defined in portasm.h */
extern void _frxt_tick_timer_init(void);

/* Defined in xtensa_context.S */
extern void _xt_coproc_init(void);


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

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

unsigned port_xSchedulerRunning = 0; // Duplicate of inaccessible xSchedulerRunning; needed at startup to avoid counting nesting
unsigned port_interruptNesting = 0;  // Interrupt nesting level

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

// User exception dispatcher when exiting
void _xt_user_exit(void);

/*
 * Stack initialization
 */
#if portUSING_MPU_WRAPPERS
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters, BaseType_t xRunPrivileged )
#else
StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
#endif
{
    StackType_t * sp;
    StackType_t * tp;
    XtExcFrame * frame;

    #if XCHAL_CP_NUM > 0
        uint32_t * p;
    #endif

    /* Create interrupt stack frame aligned to 16 byte boundary */
    sp = ( StackType_t * ) ( ( ( UBaseType_t ) pxTopOfStack - XT_CP_SIZE - XT_STK_FRMSZ ) & ~0xf );

    /* Clear the entire frame (do not use memset() because we don't depend on C library) */
    for( tp = sp; tp <= pxTopOfStack; ++tp )
    {
        *tp = 0;
    }

    frame = ( XtExcFrame * ) sp;

    /* Explicitly initialize certain saved registers */
    frame->pc = ( UBaseType_t ) pxCode;             /* task entrypoint                */
    frame->a0 = 0;                                  /* to terminate GDB backtrace     */
    frame->a1 = ( UBaseType_t ) sp + XT_STK_FRMSZ;  /* physical top of stack frame    */
    frame->exit = ( UBaseType_t ) _xt_user_exit;    /* user exception exit dispatcher */

    /* Set initial PS to int level 0, EXCM disabled ('rfe' will enable), user mode. */
    /* Also set entry point argument parameter. */
    #ifdef __XTENSA_CALL0_ABI__
        frame->a2 = ( UBaseType_t ) pvParameters;
        frame->ps = PS_UM | PS_EXCM;
    #else
        /* + for windowed ABI also set WOE and CALLINC (pretend task was 'call4'd). */
        frame->a6 = ( UBaseType_t ) pvParameters;
        frame->ps = PS_UM | PS_EXCM | PS_WOE | PS_CALLINC( 1 );
    #endif

    #ifdef XT_USE_SWPRI
        /* Set the initial virtual priority mask value to all 1's. */
        frame->vpri = 0xFFFFFFFF;
    #endif

    #if XCHAL_CP_NUM > 0
        /* Init the coprocessor save area (see xtensa_context.h) */

        /* No access to TCB here, so derive indirectly. Stack growth is top to bottom.
         * //p = (uint32_t *) xMPUSettings->coproc_area;
         */
        p = ( uint32_t * ) ( ( ( uint32_t ) pxTopOfStack - XT_CP_SIZE ) & ~0xf );
        configASSERT( ( uint32_t ) p >= frame->a1 );
        p[ 0 ] = 0;
        p[ 1 ] = 0;
        p[ 2 ] = ( ( ( uint32_t ) p ) + 12 + XCHAL_TOTAL_SA_ALIGN - 1 ) & -XCHAL_TOTAL_SA_ALIGN;
    #endif

    return sp;
}

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

void vPortEndScheduler( void )
{
    /* It is unlikely that the Xtensa port will get stopped.  If required simply
    disable the tick interrupt here. */
}

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

BaseType_t xPortStartScheduler( void )
{
    // Interrupts are disabled at this point and stack contains PS with enabled interrupts when task context is restored

    #if XCHAL_CP_NUM > 0
    /* Initialize co-processor management for tasks. Leave CPENABLE alone. */
    _xt_coproc_init();
    #endif

    /* Init the tick divisor value */
    _xt_tick_divisor_init();

    /* Setup the hardware to generate the tick. */
    _frxt_tick_timer_init();

    #if XT_USE_THREAD_SAFE_CLIB
    // Init C library
    vPortClibInit();
    #endif

    port_xSchedulerRunning = 1;

    // Cannot be directly called from C; never returns
    __asm__ volatile ("call0    _frxt_dispatch\n");

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

BaseType_t xPortSysTickHandler( void )
{
    BaseType_t ret;
    uint32_t interruptMask;

    portbenchmarkIntLatency();

    /* Interrupts upto configMAX_SYSCALL_INTERRUPT_PRIORITY must be
     * disabled before calling xTaskIncrementTick as it access the
     * kernel lists. */
    interruptMask = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        ret = xTaskIncrementTick();
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR( interruptMask );

    portYIELD_FROM_ISR( ret );

    return ret;
}
/*-----------------------------------------------------------*/

/*
 * Used to set coprocessor area in stack. Current hack is to reuse MPU pointer for coprocessor area.
 */
#if portUSING_MPU_WRAPPERS
void vPortStoreTaskMPUSettings( xMPU_SETTINGS * xMPUSettings,
                                const struct xMEMORY_REGION * const xRegions,
                                StackType_t * pxBottomOfStack,
                                uint32_t ulStackDepth )
{
    #if XCHAL_CP_NUM > 0
        xMPUSettings->coproc_area = ( StackType_t * ) ( ( uint32_t ) ( pxBottomOfStack + ulStackDepth - 1 ));
        xMPUSettings->coproc_area = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) xMPUSettings->coproc_area ) & ( ~( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK ) ) );
        xMPUSettings->coproc_area = ( StackType_t * ) ( ( ( uint32_t ) xMPUSettings->coproc_area - XT_CP_SIZE ) & ~0xf );

        /* NOTE: we cannot initialize the coprocessor save area here because FreeRTOS is going to
         * clear the stack area after we return. This is done in pxPortInitialiseStack().
         */
    #endif
}
#endif /* if portUSING_MPU_WRAPPERS */