Re: [PATCH] arm64: tegra: Enable ramoops on Tegra210 and newer

[Thierry Reding]

On Mon, Jun 30, 2025 at 01:48:28PM -0500, Aaron Kling wrote:
> On Thu, May 29, 2025 at 3:53 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
> >
> > On 28/05/2025 19:35, Aaron Kling wrote:
> > >>>>
> > >>>> Friendly reminder to the Tegra maintainers about this question.
> > >>>>
> > >>> In lieu of a response from the Tegra subsystem maintainers, I can only
> > >>> hazard an assumption, Krzysztof. I presume the pstore carveout is
> > >>> bootloader controlled because various stages of the boot stack can
> > >>> dynamically allocate memory, and this became bootloader controlled to
> > >>> prevent any of those from overwriting pstore. I worry about hardcoding
> > >>> an address in the kernel dt, then finding out later that there's an
> > >>> in-use configuration that overwrites or corrupts that section of ram
> > >>> during boot. What are your thoughts on this? And is there any way for
> > >>> this patch to proceed?
> > >>
> > >> I haven't been able to find anything out about this yet. Generally it's
> > >> difficult to get the bootloaders updated for these devices. Tegra194 and
> > >> Tegra234 may be new enough to make an update eventually go into a
> > >> release, but for Tegra186 and older, I honestly wouldn't hold my
> > >> breath.
> > >>
> > >> Thierry
> > >
> > > Krzysztof, based on this response, is there any way or form that the
> > > Tegra186 part of this could be submitted? I can drop the newer
> > > platforms from this patch if Thierry can get a response to his other
> > > reply about how the bootloader could conform.
> > >
> > I don't NAK it. Eventually it is up to platform maintainer if they
> > accept known DTC warnings.
> >
> > Best regards,
> > Krzysztof
> 
> If the decision is up the the tegra maintainers, then Thierry, what's
> your thoughts now? What is in this patch should be compatible with
> existing l4t and android bootloaders. But it does add a few new dtb
> check lines.

I don't adding new DTC warnings, especially ones that we know up front
we can never get rid of. The memory one is a notable exception because
the system becomes unusable without it.

ramoops is not in that same category. While it's certainly nice to have,
I don't think it's critical enough to warrant that permanent exception.
Where possible I think we need to work to address issues souch as this
at the root and fix bootloaders to do the right thing.

For any cases where we can't fix the bootloaders, I think that's
something we have to live with. Having the support for this live in a
fork is a fair compromise, I think.

I know this is frustrating, and it's very painful for me personally
because I initially set out to redress a lot of these things and failed
to do so.

However I can't justify accepting endless amounts of quirks upstream,
all of which would set a bad precedent, just for the sake of things
being upstream.

Thierry

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