Re: [PATCH 0/2] arch: arm: gic-v3-its: stop abusing the device tree

Marc Zyngier
2021-10-28T14:42:56Z

On Thu, 28 Oct 2021 12:21:59 +0100,
Michael Walle <michael@walle.cc> wrote:
>
> Am 2021-10-28 11:20, schrieb Bharat Gooty:
> > On Thu, Oct 28, 2021 at 2:33 PM Marc Zyngier <maz@kernel.org> wrote:
>
> > For GIC V3, once the LPI tables are programmed, we can not update it,
> > unless we do a reset.
> > For the kexec kernel, where the reboot does not happen, in this case,
> > during the new kernel boot, the new LPI tables address will not be
> > updated.
>
> kexec.. this should have really gone into both the commit message _and_
> the kconfig menu. In fact, it is really just a workaround for the kexec
> case. If I understand it correctly, the kernel is able to communicate
> the reserved memory area, but only if you have EFI support. So, as a
> workaround, the bootloader can pre-allocate the memory and put it in
> the device tree, which is then passed from the old to the new kernel
> and the reservation is preserved. Correct, Marc?

See my reply to Bharat. Either you use EFI, or you reserve the memory
and program the RDs. In either of these two cases, kexec will just work.

> But all of this doesn't need any new device tree node.

Exactly. The whole syscon stuff is a point hack that makes no sense,
and which isn't parsed by any upstream SW.

M.

--
Without deviation from the norm, progress is not possible.