[PATCH] [RFC] lmb: Optionally limit available memory to 4 GiB on limited systems

[Ilias Apalodimas]

On Wed, 3 Jun 2026 at 14:12, Marek Vasut <marek.vasut at mailbox.org> wrote:
>
> On 6/3/26 12:37 PM, Ilias Apalodimas wrote:
>
> Hello Ilias,
>
> >>> diff --git a/lib/Kconfig b/lib/Kconfig
> >>> index 77ebc79e1db..29911068a69 100644
> >>> --- a/lib/Kconfig
> >>> +++ b/lib/Kconfig
> >>> @@ -1295,6 +1295,14 @@ config SPL_LMB_ARCH_MEM_MAP
> >>>          memory map. Enable this config in such scenarios which allow
> >>>          architectures and boards to define their own memory map.
> >>>
> >>> +config LMB_LIMIT_DMA_BELOW_4G
> >
> > This seems the right idea for now, but is it really 4G or ram_top?
> I think the LMB configuration should in fact be board (or SoC) specific,
> because RPi has problems already at 1 GiB, other hardware might have
> problems at 4 GiB, etc. But this config option is the generic "make it
> work somehow" flip switch.

yea agree on that. I was just commenting on the Kconfig name
Cheers
/Ilias