i.MX8MP SPL failures due to memory corruption/overflow?

[Michael Nazzareno Trimarchi]

Hi

On Wed, Mar 15, 2023 at 3:13 PM Frieder Schrempf
<frieder.schrempf at kontron.de> wrote:
>
> Hi,
>
> I'm trying to bring up a new board based on the i.MX8MP and I have an
> issue I'm hoping someone can help solving.
>
> I'm seeing failures in the early SPL code, usually in the DDR
> initialization. Often they look like:
>
>   U-Boot SPL 2023.04-rc3 (Mar 07 2023 - 14:32:34 +0000)
>   Training FAILED
>   Failed to initialize DDR RAM!
>   ### ERROR ### Please RESET the board ###
>
> But sometimes ddr_init() doesn't even return an error and only the
> get_ram_size() afterwards which tries to allocate the memory fails.
>

In my experience you don't have space inside the cpu internal memory. It means
that you overlap some stack with the code. Change the printf means
move a bit. So you have
problem but depends what you are going to destroy

Michael

> The strange thing is that the issues appear or disappear
> deterministically on the binary level. This means I sometimes get a
> U-Boot binary which runs just fine in 100% of cases. Then I change for
> example one of the following:
>
> * Adding a single printf() somewhere in the boards spl.c
> * Using the same binary but booting from SD card instead of USB loader
> * Using the same source but switching from the OS cross compiler to the
> one from Yocto/OE
>
> And afterwards I get 100% failure rate with an error as described above.
>
> My suspicion is that there is some memory corruption/conflict. My SPL is
> quite large and I wonder if it exceeds some limit.
>
> SPL is loaded to 0x920000 and CONFIG_SPL_STACK is set to 0x960000, which
> leaves 256 KiB in between for the SPL. But all i.MX8MP boards seem to
> set CONFIG_SPL_MAX_SIZE=0x26000 (152 KiB) for some reason. My
> u-boot-spl-ddr.bin currently has around 193 KiB but I don't get any
> warning about exceeding the SPL_MAX_SIZE.
>
> My questions:
>
> * Why is CONFIG_SPL_MAX_SIZE set to 152 KiB?
> * Why is there no warning in my case?
> * Any other ideas or pointers?
>
> Thanks for your help!
>
> Best regards
> Frieder



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Michael Nazzareno Trimarchi
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