[PATCH v1 3/3] common: Allow relocations on the top of the last bank

[Marek Vasut]

On 3/27/26 1:23 PM, Ilias Apalodimas wrote:

Hello Ilias,

>>> Add a Kconfig option and allow the common code to relocate U-Boot
>>> to the top of the last discovered bank.
>>
>> The commit message should really clarify the current pitfalls of
>> enabling this symbol, including the part where ethernet transfers above
>> 4 GiB used to work because of the packet buffer built into U-Boot, and
>> they will break because the buffer is now relocated above 4 GiB too.
> 
> Shall I just add your note from the RFC with a few adjustments? I.e
> 
> NOTE: This currently might break platforms. If the ethernet
>        controller cannot DMA above 4 GiB, and once U-Boot does
>        get relocated above 4 GiB, the packet buffer which is built
>        into the U-Boot binary is also relocated above 4 GiB.

This patch should not be applied in the first place, this DOES break 
things. I think when this patch is safe to be applied, the note will not 
be needed.

[...]
>>> +++ b/common/board_f.c
>>> @@ -321,6 +321,8 @@ __weak phys_addr_t board_get_usable_ram_top(phys_size_t total_size)
>>>                 */
>>>                return 0;
>>>    #endif
>>> +     if (IS_ENABLED(CONFIG_RELOCATE_LAST_BANK))
>>> +             fdtdec_setup_mem_ram_top();
>> Return value may need checking ?
> 
> sure, but should we panic ? Or print a message and silently keep the
> old reloc address?
Print a message and relocate below 4 GiB , for maximum compatibility maybe ?