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Linux: U-boot load address for MLO

ranchu
Guru 20755 points


Tool/software: Linux

Hello,

I am trying to load a standalone program from MLO running from nand flash.

By default MLO load address in code is 0x80008000 , and U-boot from git starts successfully with it.

I first needed to run a standalone which output is expected to loaded into 0x80000000 (uc/os) , so I changed the load address from 0x80008000  to 0x80000000 and the application started OK.

Then I just checked if u-boot can also run with the same MLO (which load into 0x80000000 ), and surprisingly it started without issues.

Can anyone explain this  ?

Thank you,

Ran 

  • 0
    Guru 13660 points

    Hi Ranchu,

    Since MLO copies the uboot or any code into known location in RAM like 0x80008000(or 0x80000000), MLO can also make sure the execution jumps to this location. As long as location is valid and as long as there are no overlaping reserved region(like arguments being passed to uboot from MLO). since if there is reserved region, it would corrupt this region, it should work.

  • 0 in reply to Dwarakesh Radhakrishnan
    Guru 20755 points
    Hi Dwarakesh,

    I forgot to mention that I didn't make any change in u-boot.bin after changing the MLO load address to 0x80000000.
    So what I don't yet understand:
    Wwhy with one application (uc/os) it should matter that the address shall be 0x80000000, and the other application (u-boot) doesn't matter if it is 0x80000000 or 0x80008000 (same bin file gets started in both!)

    Thank you!
    Ran
  • 0 in reply to ranchu
    Guru 13660 points
    Hi Ranchu,

    From where uboot is loaded is not required for uboot to know, unless some memory region is hardcoded in it for its usage and that memory region overlaps with the uboot loaded address. Which may not be the case.