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Original question:

[FAQ] AM263P4: Enabling XIP in AM263PX

AM263P4: Enabling XIP for SBL

Sebastien Chapeau
Intellectual 270 points
Part Number: AM263P4

Tool/software:

Hi

For our project I would like to enable XIP for the SBL.

Starting from the OSPI SBL example I can't seem to figure how to do this.

The reason behind this requirement to leave a maximum of space in RAM for the multicore application that will be loaded to execute next.

I think I can contain the "RAM" required by the SBL in TCMB but I'd like to leave at little as possible in OCM.

At the moment by project would build ok but the gen image fails

[110]Traceback (most recent call last):
[111] File "C:\ti\mcu_plus_sdk_am263px_10_00_00_35\source\security\security_common\tools\boot\signing\mcu_rom_image_gen.py", line 441, in <module>
[112] raise Exception(except_msg)
[113]Exception: SBL/HSM size should be less than 983000

Would you have a step by step guide on how to achieve this ?

Thanks a lot for you help.

Regards

Seb

  • 0
    Mastermind 7965 points
    Sebastien Chapeau said:
    For our project I would like to enable XIP for the SBL.

    I don't think that is possible. According to the following document: ROM Boot Flow in AM26x devices the SBL location is fixed in OCRAM at 0x70002000.

    You may reclaim this RAM in your application code by using it for variables only but of course you cannot place program code (.text) there.

  • 0 in reply to Kier
    Intellectual 270 points

    Hi

    I'm not sure how the SBL will be different from another application running in XIP.

    Effectively with the boot flow, the ROM Bootloader expect a starting point at 0x70002000 and some initialisation code will be copied into TCMA at address 0.

    If the main is in RAM but the rest of the .text "point" to flash wouldn't that work ?

    The concern here is the size of the bootloader whose code size is estimated at ~0x60000 + All its RAM requirements.

    The current ospi sbl example needs already ~91kB. Assuming all RAM requirements can be contained within TCM, that still leaves ~0.5MB "empty" after the application has been loaded.

    The application can reclaim some space using this area as shared memory or other stuff but it is quite a lot of space hence why the idea is to minimize this.

    Appreciate the boot flow need to be respected but would the principle described above work ?

    If yes, then would you be able to help on what is required and how to achieve this ?

    Looking forward to reading from you.

    Regards

    Seb

  • 0 in reply to Sebastien Chapeau
    Mastermind 7965 points
    Sebastien Chapeau said:
    If the main is in RAM but the rest of the .text "point" to flash wouldn't that work ?

    You could well be right. I guess I'll leave it to TI to answer.

  • 0
    TI__Genius 11736 points

    Hi Seb,

    As rightly pointed out by Kier, XIP for SBL is not possible. The SBL location is fixed in OCRAM and reserved, the best you can do here to save on memory is to reclaim the SBL reserved space in your application once the bootloader switches to the application. 

    Regards,
    Shaunak

  • 0 in reply to Shaunak Deshpande
    Intellectual 270 points

    Hi

    OK thanks or the clarification.

    I was also trying another venue to minimize the SBL footprint in OCM.

    Your help with this thread would be really appreciated :e2e.ti.com/.../5537231

    Regards

    Seb