Re: [PATCH v2 16/18] hw/arm/fsl-imx8mp: Add boot ROM

[Bernhard Beschow <shentey@gmail.com>]

Am 25. Februar 2025 14:29:15 UTC schrieb Peter Maydell <peter.maydell@linaro.org>:
>On Sun, 23 Feb 2025 at 11:47, Bernhard Beschow <shentey@gmail.com> wrote:
>>
>> On a real device, the boot ROM contains the very first instructions the CPU
>> executes. Also, U-Boot calls into the ROM to determine the boot device. While
>> we're not actually implementing this here, let's create the infrastructure and
>> add a dummy ROM with all zeros. This allows for implementing a ROM later without
>> touching the source code and even allows for users to provide their own ROMs.
>>
>> The imx8mp-boot.rom was created with
>> `dd if=/dev/zero of=imx8mp-boot.rom bs=1 count=258048`.
>>
>> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
>
>Hi; I've thought about this a bit, and I think we should just
>postpone having code to load a rom blob until we have an
>actual rom blob that's not all zeroes. This makes this
>board the same as e.g. imx7 which also doesn't try to load
>a ROM blob. You can create a memory region for the ROM,
>like imx7; just don't load anything into it, and that's
>exactly the same as if there was an all-zeroes file that
>got loaded.
>
>This doesn't prevent users from experimenting with providing
>their own ROM code, because they can do that with the
>generic loader (passing it either an ELF file set up to
>load to the ROM area or else a binary blob plus the
>start address of 0).
>
>That way we aren't carrying code we aren't using and an
>awkward binary blob in git; we can add those when we need
>them.

Yes, makes sense.

Best regards,
Bernhard

>
>thanks
>-- PMM