关于const定义的数据不能正确初始化的问题SDRAM

只看该作者 · 2011-8-4 14:25

本帖最后由有意思于 2011-8-4 14:35 编辑

在uboot中定义一个const的数组 unsigned char const gImage_0[48] = { /* 0X00,0X04,0X40,0X01,0XF0,0X00, */
0XCD,0XDD,0XDD,0XDD,0XDD,0XDD,0XDD,0XDD,0XDD,0XDD,0XDD,0XCC,0XDC,0XCC,0XCC,0XCC,
0XCC,0XCC,0XCC,0XCC,0XCC,0XCC,0XCC,0XCC,0XCC,0XCC,0XCB,0XBB,0XBB,0XBB,0XBB,0XBB,
0XBB,0XBB,0XBB,0XAA,0XAA,0XAA,0XAA,0XAA,0XAA,0XAA,0X99,0X99,0X99,0X99,0X99,0X99
};

这个数组在上电时打出的数据时0xFF 为什么

只看该作者 · 2011-8-4 14:42

const修饰的变量一般被编译器存储在只读区，作为只读常量，我的编译器是arm-gcc-linux
在uboot中定义这样一个全局常量，但是这个数组是在什么时候初始化的，如果初始化的时候SDRAM
还没有做初始化，那么是不是就会出现异常数据，
系统的初始化过程是这样的
uboot的start.s中调用lowlevel_init进行初始化，lowlevel_init中对memap，pll dram等进行初始化
其代码如下：

void
lowlevel_init(void)
{

  /********************************************************************************************
* Remap vectors for RAM execution
********************************************************************************************/
  MEMMAP = 1;

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
/* move vectors to beginning of SRAM */
asm volatile("  mov r2, #0x40000000\n"
               "  mov r0, #0x00000000\n"
               "  ldmneia r0!, {r3-r10}\n"
               "  stmneia r2!, {r3-r10}\n"
               "  ldmneia r0, {r3-r9}\n"
               "  stmneia r2, {r3-r9}\n" : : :
      "r0","r2","r3","r4","r5","r6","r7","r8","r9","r10");
#else
  /* move vectors to beginning of SRAM */
  asm volatile("  mov r2, #0x40000000\n"
            "  mov r0, #0xa0000000\n"
            "  ldmneia r0!, {r3-r10}\n"
            "  stmneia r2!, {r3-r10}\n"
            "  ldmneia r0, {r3-r9}\n"
            "  stmneia r2, {r3-r9}\n" : : :
      "r0", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10");
#endif

  //initialize the exception vector mapping
  MEMMAP = MEM_MAP;

#if USE_USB
PCONP |= 0x80000000; /* Turn On USB PCLK */
#endif

  ConfigurePLL();

  /* Set system timers for each component */
#if (Fpclk / (Fcclk / 4)) == 1
PCLKSEL0 = 0x00000000; /* PCLK is 1/4 CCLK */
PCLKSEL1 = 0x00000000;
#endif
#if (Fpclk / (Fcclk / 4)) == 2
PCLKSEL0 = 0xAAAAAAAA; /* PCLK is 1/2 CCLK */
PCLKSEL1 = 0xAAAAAAAA;
#endif
#if (Fpclk / (Fcclk / 4)) == 4
PCLKSEL0 = 0x55555555; /* PCLK is the same as CCLK */
PCLKSEL1 = 0x55555555;
#endif

  /* Set memory accelerater module*/
//  MAMCR  = 0;
//  MAMTIM = 4;
  MAMCR  = 0;
  MAMTIM = 3;
  MAMCR  = 2;

  //Init GPIO
  GPIOinit();

  //initialize VIC
  VICinit();

  //initialize UART #0 to 38400, 8N1
  UART0init();

#ifndef USE_32_BIT_DATABUS
//initialize UART #1
UART1init();
#endif
//short delay
delayMs(10);

  /********************************************************************************************
* Initialize external memory interface (EMC)
********************************************************************************************/
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
ConfigureEMC();
#endif

      LcdInit();//gimag_0的数据在该函数中打出来，
}
、
1. 掉电1分钟后，在上电，打出的数据全部为0xFF
2. 快速的断电，上电，断电上电，打出数据，是正确的
3.在上电后，并且进入linux内核GUI以前进行热复位，通过HJTAG，打印，是正确的
4.在进入linux的GUI之后热复位，打印的是错误，且数据是随机的

问题会出在哪个部分？？