/****************************************************************************
 * arch/arm/src/efm32/efm32_start.c
 *
 *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <assert.h>
#include <debug.h>

#include <nuttx/init.h>
#include <nuttx/syslog/syslog.h>

#include <arch/board/board.h>
#include <arch/efm32/chip.h>

#include "up_arch.h"
#include "up_internal.h"
#include "efm32_config.h"
#include "efm32_lowputc.h"
#include "efm32_clockconfig.h"
#include "efm32_start.h"

/****************************************************************************
 * Private Function prototypes
 ****************************************************************************/

#ifdef CONFIG_DEBUG_STACK
static void go_os_start(void *pv, unsigned int nbytes)
  __attribute__ ((naked,no_instrument_function,noreturn));
#endif

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: showprogress
 *
 * Description:
 *   Print a character on the UART to show boot status.
 *
 ****************************************************************************/

#ifdef CONFIG_DEBUG
#  if defined(CONFIG_ARMV7M_ITMSYSLOG)
#    define showprogress(c) (void)syslog_putc(c)
#  elif defined(HAVE_UART_CONSOLE) || defined(HAVE_LEUART_CONSOLE)
#    define showprogress(c) up_lowputc(c)
#  else
#    define showprogress(c)
#  endif
#else
#  define showprogress(c)
#endif

/****************************************************************************
 * Name: go_os_start
 *
 * Description:
 *   Set the IDLE stack to the
 *
 ****************************************************************************/

#ifdef CONFIG_DEBUG_STACK
static void go_os_start(void *pv, unsigned int nbytes)
{
  /* Set the IDLE stack to the stack coloration value then jump to
   * os_start().  We take extreme care here because were currently
   * executing on this stack.
   *
   * We want to avoid sneak stack access generated by the compiler.
   */

  __asm__ __volatile__
  (
    "\tmov  r1, r1, lsr #2\n"   /* R1 = nwords = nbytes >> 2 */
    "\tbeq  2f\n"               /* (should not happen) */

    "\tbic  r0, r0, #3\n"       /* R0 = Aligned stackptr */
    "\tmovw r2, #0xbeef\n"      /* R2 = STACK_COLOR = 0xdeadbeef */
    "\tmovt r2, #0xdead\n"

    "1:\n"                      /* Top of the loop */
    "\tsub  r1, r1, #1\n"       /* R1 nwords-- */
    "\tcmp  r1, #0\n"           /* Check (nwords == 0) */
    "\tstr  r2, [r0], #4\n"     /* Save stack color word, increment stackptr */
    "\tbne  1b\n"               /* Bottom of the loop */

    "2:\n"
    "\tmov  r14, #0\n"          /* LR = return address (none) */
    "\tb    os_start\n"         /* Branch to os_start */
  );
}
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: _start
 *
 * Description:
 *   This is the reset entry point.
 *
 ****************************************************************************/

void __start(void)
{
  const uint32_t *src;
  uint32_t *dest;

  /* Configure the uart so that we can get debug output as soon as possible */

  efm32_clockconfig();
  efm32_lowsetup();
  showprogress('A');

  /* Clear .bss.  We'll do this inline (vs. calling memset) just to be
   * certain that there are no issues with the state of global variables.
   */

  for (dest = &_sbss; dest < &_ebss; )
    {
      *dest++ = 0;
    }

  showprogress('B');

  /* Move the initialized data section from his temporary holding spot in
   * FLASH into the correct place in SRAM.  The correct place in SRAM is
   * give by _sdata and _edata.  The temporary location is in FLASH at the
   * end of all of the other read-only data (.text, .rodata) at _eronly.
   */

  for (src = &_eronly, dest = &_sdata; dest < &_edata; )
    {
      *dest++ = *src++;
    }

  showprogress('C');

  /* Perform early serial initialization */

  up_earlyserialinit();

  showprogress('D');

  /* For the case of the separate user-/kernel-space build, perform whatever
   * platform specific initialization of the user memory is required.
   * Normally this just means initializing the user space .data and .bss
   * segments.
   */

#ifdef CONFIG_NUTTX_KERNEL
  efm32_userspace();
  showprogress('E');
#endif

  /* Then start NuttX */

  showprogress('\r');
  showprogress('\n');

#ifdef CONFIG_DEBUG_STACK
  /* Set the IDLE stack to the coloration value and jump into os_start() */

  go_os_start((FAR void *)&_ebss, CONFIG_IDLETHREAD_STACKSIZE);
#else
  /* Call os_start() */

  os_start();

  /* Shouldn't get here */

  for(;;);
#endif
}