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Altera_Forum's avatar
Altera_Forum
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15 years ago

Boot_link_offset

Hi all,

I'm trying to configure linux kernel (with MMU) for my demo board...but it is not clear to me the meaning of BOOT_LINK_OFFSET in kernel configuration....

What exactly does it mean???

Hope someone can explain...

Thanks

Carlo

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    I answer to myself...hope can help other people...

    from nioswiki

    The zImage load address is ( your sdram base address + link address offset ).

    The boot loader will uncompress the code to the beginning of sdram. If the uncompressed code is bigger than the default 5M, the two area will overlap and corrupt.

    The compressed image offset should be adjusted to a higher value when the kernel image is big, eg, large files in romfs dir.

    You can change this value to about 2/3 of the size of your sdram, eg, 20M out fo 32M. I suggest 2/3 because the gzip compression ratio is about 1:2. The zImage boot loader does not relocate/move itself.

    In other words zImage start at sdram base address + link address offset then uncompress itself starting from sdram base address...the 2 regions must not overlap

    If there is any additional info please post on this thread..

    Carlo