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

[Ilias Apalodimas]

On Sat, 28 Mar 2026 at 08:44, Marek Vasut <marek.vasut at mailbox.org> wrote:
>
> 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.

The patch obviously will not get applied. I was referring to the note
in the commit message only.
I'll just add it with slight changes in the commit

>
> [...]
> >>> +++ 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 ?

Yea that's what I currently have on my local branch

Cheers
/Ilias