UBootCrashAfterRelocation < DULG

%SECTION0{name=UBootCrashAfterRelocation}% U-Boot crashes after relocation to RAM

   Question:: I have ported U-Boot to a custom board. It starts OK, but crashes or
    hangs after relocating itself to RAM. Why?
 
   Answer:: Your SDRAM initialization is bad, and the system crashes when it
    tries to fetch instructions from RAM. Note that simple read and write
    accesses may still work, it's the *burst* mode that is failing.  This only
    shows up when caches are enabled because cache is the primary (or only) user
    of burst operations in U-Boot. In Linux, burst accesses may also result from
    DMA. For example, it is typical that a system may crash under heavy network load
    if the Ethernet controller uses DMA to memory.
    <p></p>
    %X% It is *NOT* sufficient to program the memory controller of your CPU;
    each SDRAM chip also requires a specific initialization sequence which you
    must adhere to *to the letter* - check with the chip manufacturer's
    manual.
    <p></p>
    It has been observed that some operating systems like pSOS+ or <nop>VxWorks
    do not stress the memory subsystem
    as much as Linux or other UNIX systems like <nop>LynxOS do,
    so just because your board appears to work running another OS
    does not mean it is 100% OK.
    <p></p>
    Standard memory tests are not effective in identifying this type of problem because
    they do not cause stressful cache burst read/write operations.
    <p></p>
    With this caveat in mind, reportedly this program has found memory problems before:
    http://pyropus.ca/software/memtester/

   Argument:: But my board ran fine with bootloader XYZ and/or operating system ABC.

   Answer:: Double-check your configuration that you claim runs properly...
   <p></p>
      1 Are you *sure* the SDRAM is initialized using the same init sequence and values?
      1 Are you *sure* the memory controlling registers are set the same?
      1 Are you *sure* your other configuration uses caches and/or DMA?  If it doesn't,
         it isn't a valid comparison.
14.2.3. Source object has EABI version 4, but target has EABI version 0		1. Abstract		14.2.5. Warning - bad CRC, using default environment
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