mccibootloaderplatform_startapp.c

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/*
 
Module: mccibootloaderplatform_startapp.c
 
Function:
        McciBootloaderPlatform_startApp()
 
Copyright and License:
        This file copyright (C) 2021 by
 
                MCCI Corporation
                3520 Krums Corners Road
                Ithaca, NY  14850
 
        See accompanying LICENSE file for copyright and license information.
 
Author:
        Terry Moore, MCCI Corporation   March 2021
 
*/
 
#include "mcci_bootloader_platform.h"
 
#include "mcci_bootloader_bits.h"
#include "mcci_arm_cm0plus.h"
#include <stdint.h>
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|       Manifest constants & typedefs.
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/****************************************************************************\
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|       Read-only data.
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/****************************************************************************\
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|       Variables.
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/*
 
Name:   McciBootloaderPlatform_startApp()
 
Function:
        Launch application from bootloader.
 
Definition:
        void McciBootloaderPlatform_startApp(
                const void *pAppBase
                );
 
Description:
        pAppBase points to the base of the application image in memory, which
        is assumed to conform to any platform-specific requirements. The
        application is launched. If the launch fails,
        McciBootloaderPlatform_fail() is invoked. This function does not
        return to the caller.
 
Returns:
        No explicit result.
 
Notes:
        On a Cortex M0+ or similar processor, pAppBase points to the vectors
        of the app being invoked. The first dword is the stack pointer, and
        the second dword is the start address.
 
        In a full implementation, the bootloader should shutdown all
        peripherals it has setup, and establish a default condition for
        launching the app. In principal, the app should be entered as if
        it had received control from a reset. This is to some degree a
        matter of taste and design rather than a logical requirement.
 
*/
 
#define FUNCTION "McciBootloaderPlatform_startApp"
 
void
McciBootloaderPlatform_startApp(
        const void *pAppBase
        )
        {
        const Mcci_CortexAppEntryContents_t * const pAppVectors = pAppBase;
        const uint32_t stack = pAppVectors->stack;
        const uint32_t pc = pAppVectors->entry;
 
        // Oddly, interrupts are enabled on launch, so we have to
        // deal with that below.
        McciArm_disableInterrupts();
 
        // Do the SOC-specific things to get us ready;
        McciBootloaderPlatform_prepareForLaunch();
 
        // set the stack pointer
        McciArm_setMSP(stack);
 
        // set the vector address
        McciArm_putReg(
                MCCI_CM0PLUS_SCB_VTOR,
                (uint32_t) pAppVectors & MCCI_CM0PLUS_SCB_VTOR_TBLOFF
                );
 
        // go to the app: enable interrupts and jump.
        __asm volatile ("cpsie i" ::: "memory");
        __asm volatile ("bx %0" :: "r"(pc));
        __builtin_unreachable();
        }
 
#undef FUNCTION
 
 
/**** end of mccibootloaderplatform_startapp.c ****/