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3f67c67aaf
All supported arch uses a push-down stack: The stack grows toward lower addresses in memory. The stack pointer register points to the lowest, valid working address (the "top" of the stack). Items on the stack are referenced as positive(include zero) word offsets from sp. Which means that for stack in the [begin, begin + size): 1.The initial SP point to begin + size 2.push equals sub and then store 3.pop equals load and then add Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
164 lines
4.9 KiB
C
164 lines
4.9 KiB
C
/****************************************************************************
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* arch/arm/src/samd2l2/sam_start.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <assert.h>
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#include <debug.h>
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#include <nuttx/init.h>
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#include "arm_arch.h"
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#include "arm_internal.h"
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#include "sam_config.h"
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#include "sam_lowputc.h"
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#include "sam_clockconfig.h"
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#include "sam_userspace.h"
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#include "sam_start.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Memory Map:
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*
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* 0x0000:0000 - Beginning of FLASH. Address of exception vectors.
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* 0x0003:ffff - End of flash (assuming 256KB of FLASH)
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* 0x2000:0000 - Start of SRAM and start of .data (_sdata)
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* - End of .data (_edata) abd start of .bss (_sbss)
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* - End of .bss (_ebss) and bottom of idle stack
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* - _ebss + CONFIG_IDLETHREAD_STACKSIZE = end of idle stack,
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* start of heap
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* 0x2000:ffff - End of SRAM and end of heap (assuming 64KB of SRAM)
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*/
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#define IDLE_STACK ((uint32_t)&_ebss+CONFIG_IDLETHREAD_STACKSIZE)
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/****************************************************************************
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* Public Data
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****************************************************************************/
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const uintptr_t g_idle_topstack = IDLE_STACK;
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: showprogress
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*
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* Description:
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* Print a character on the UART to show boot status.
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*
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****************************************************************************/
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#if defined(CONFIG_DEBUG_FEATURES) && defined(HAVE_SERIAL_CONSOLE)
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# define showprogress(c) sam_lowputc((uint32_t)c)
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#else
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# define showprogress(c)
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: _start
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*
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* Description:
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* This is the reset entry point.
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*
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****************************************************************************/
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void __start(void)
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{
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const uint32_t *src;
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uint32_t *dest;
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/* Clear .bss. We'll do this inline (vs. calling memset) just to be
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* certain that there are no issues with the state of global variables.
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*/
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for (dest = &_sbss; dest < &_ebss; )
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{
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*dest++ = 0;
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}
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/* Move the initialized data section from his temporary holding spot in
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* FLASH into the correct place in SRAM. The correct place in SRAM is
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* give by _sdata and _edata. The temporary location is in FLASH at the
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* end of all of the other read-only data (.text, .rodata) at _eronly.
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*/
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for (src = &_eronly, dest = &_sdata; dest < &_edata; )
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{
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*dest++ = *src++;
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}
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/* Configure basic clocking */
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sam_clockconfig();
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/* Configure the uart early so that we can get debug output as soon as
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* possible
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*/
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sam_lowsetup();
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showprogress('A');
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/* Perform early serial initialization */
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#ifdef USE_EARLYSERIALINIT
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arm_earlyserialinit();
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#endif
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showprogress('B');
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/* For the case of the separate user-/kernel-space build, perform whatever
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* platform specific initialization of the user memory is required.
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* Normally this just means initializing the user space .data and .bss
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* segments.
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*/
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#ifdef CONFIG_BUILD_PROTECTED
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sam_userspace();
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showprogress('C');
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#endif
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/* Initialize onboard resources */
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sam_boardinitialize();
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showprogress('D');
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/* Then start NuttX */
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showprogress('\r');
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showprogress('\n');
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nx_start();
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/* Shouldn't get here */
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for (; ; );
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}
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