/*
    FreeRTOS V8.2.1 - Copyright (C) 2015 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    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 modification 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.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS provides completely free yet professionally developed,    *
     *    robust, strictly quality controlled, supported, and cross          *
     *    platform software that is more than just the market leader, it     *
     *    is the industry's de facto standard.                               *
     *                                                                       *
     *    Help yourself get started quickly while simultaneously helping     *
     *    to support the FreeRTOS project by purchasing a FreeRTOS           *
     *    tutorial book, reference manual, or both:                          *
     *    http://www.FreeRTOS.org/Documentation                              *
     *                                                                       *
    ***************************************************************************

    http://www.FreeRTOS.org/FAQHelp.html - Having a problem?  Start by reading
    the FAQ page "My application does not run, what could be wrong?".  Have you
    defined configASSERT()?

    http://www.FreeRTOS.org/support - In return for receiving this top quality
    embedded software for free we request you assist our global community by
    participating in the support forum.

    http://www.FreeRTOS.org/training - Investing in training allows your team to
    be as productive as possible as early as possible.  Now you can receive
    FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
    Ltd, and the world's leading authority on the world's leading RTOS.

    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
    including FreeRTOS+Trace - an indispensable productivity tool, a DOS
    compatible FAT file system, and our tiny thread aware UDP/IP stack.

    http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
    Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.

    http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
    Integrity Systems ltd. to sell under the OpenRTOS brand.  Low cost OpenRTOS
    licenses offer ticketed support, indemnification and commercial middleware.

    http://www.SafeRTOS.com - High Integrity Systems also provide a safety
    engineered and independently SIL3 certified version for use in safety and
    mission critical applications that require provable dependability.

    1 tab == 4 spaces!
*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ARM CM4F port.
 *----------------------------------------------------------*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/*
 * Start first task is a separate function so it can be tested in isolation.
 */
__stackless void vPortStartFirstTask( void );

/*
 * Exception handlers.
 */
__stackless void vPortSVCHandler( void );
__stackless void xPortPendSVHandler( void );


extern uint32_t __Vectors;
extern uint32_t pxCurrentTCB;


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

__stackless void vPortStartFirstTask( void )
{
    __asm volatile(
                    " ldr.n r0, 1f          \n" /* Locate the stack using __Vectors table. */
                    " ldr r0, [r0]          \n"
                    " msr msp, r0           \n" /* Set the msp back to the start of the stack. */
                    " cpsie i               \n" /* Globally enable interrupts. */
                    " cpsie f               \n"
                    " dsb                   \n"
                    " isb                   \n"
#ifdef SOFTDEVICE_PRESENT
                    /* Block kernel interrupts only (PendSV) before calling SVC */
                    " mov r0, %1           \n"
                    " msr basepri, r0       \n"
#endif
                    " svc 0                 \n" /* System call to start first task. */
                    "                       \n"
                    " nop                   \n" /* Manual alignment of the label below */
                    "1:                     \n"
                    "   DC32  %c0           \n"
                    : /* Outputs */
                    : /* Inputs */
                        "i"(&__Vectors)
#ifdef SOFTDEVICE_PRESENT
                        ,
                        "i"(configKERNEL_INTERRUPT_PRIORITY  << (8 - configPRIO_BITS))
#endif
                );
}

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

__stackless void vPortSVCHandler( void )
{
    __asm volatile (
                    "   ldr.n r3, 1f                    \n" /* Restore the context. */
                    "   ldr r1, [r3]                    \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
                    "   ldr r0, [r1]                    \n" /* The first item in pxCurrentTCB is the task top of stack. */
                    "   ldmia r0!, {r4-r11, r14}        \n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */
                    "   msr psp, r0                     \n" /* Restore the task stack pointer. */
                    "   isb                             \n"
                    "   mov r0, #0                      \n"
                    "   msr basepri, r0                 \n"
                    "   bx r14                          \n"
                    "                                   \n"
                    "                                   \n" /* Manual alignment of the label below */
                    "1:                                 \n"
                    "   DC32  %c0                       \n"
                    : /* Outputs */
                    : /* Inputs */
                        "i"(&pxCurrentTCB)
                );
}

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

__stackless void xPortPendSVHandler( void )
{
    /* This is a naked function. */

    __asm volatile
    (
    "   mrs r0, psp                         \n"
    "   isb                                 \n"
    "                                       \n"
    "   ldr.n r3, 1f                        \n" /* Get the location of the current TCB. */
    "   ldr r2, [r3]                        \n"
    "                                       \n"
    "   tst r14, #0x10                      \n" /* Is the task using the FPU context?  If so, push high vfp registers. */
    "   it eq                               \n"
    "   vstmdbeq r0!, {s16-s31}             \n"
    "                                       \n"
    "   stmdb r0!, {r4-r11, r14}            \n" /* Save the core registers. */
    "                                       \n"
    "   str r0, [r2]                        \n" /* Save the new top of stack into the first member of the TCB. */
    "                                       \n"
    "   stmdb sp!, {r3}                     \n"
    "   mov r0, %0                         \n"
    "   msr basepri, r0                     \n"
    "   dsb                                 \n"
    "   isb                                 \n"
    "   bl %c2                              \n"
    "   mov r0, #0                          \n"
    "   msr basepri, r0                     \n"
    "   ldmia sp!, {r3}                     \n"
    "                                       \n"
    "   ldr r1, [r3]                        \n" /* The first item in pxCurrentTCB is the task top of stack. */
    "   ldr r0, [r1]                        \n"
    "                                       \n"
    "   ldmia r0!, {r4-r11, r14}            \n" /* Pop the core registers. */
    "                                       \n"
    "   tst r14, #0x10                      \n" /* Is the task using the FPU context?  If so, pop the high vfp registers too. */
    "   it eq                               \n"
    "   vldmiaeq r0!, {s16-s31}             \n"
    "                                       \n"
    "   msr psp, r0                         \n"
    "   isb                                 \n"
    "                                       \n"
    "                                       \n"
    "   bx r14                              \n"
    "                                       \n"
    "                                       \n" /* Manual alignment of the label below */
    "1:                                     \n"
    "   DC32  %c1                           \n"
    : /* Outputs */
    : /* Inputs */
        "i"(configMAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS)),
        "i"(&pxCurrentTCB),
        "i"(&vTaskSwitchContext)
    );
}
