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

Marc Zyngier
2021-10-28T09:49:26Z

On Thu, 28 Oct 2021 10:20:53 +0100,
Bharat Gooty <bharat.gooty@broadcom.com> wrote:
>
> For GIC V3, once the LPI tables are programmed, we can not update it,
> unless we do a reset.

Please tell me something I don't know...

> 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.

Since July 2018, the Linux kernel is perfectly able to deal with this
without any extra support. It will communicate the reservation to the
secondary kernel, and the secondary kernel will happily use this.

> For these reasons, We allocate the LPI table memory in u-boot and
> reserve that memory.

What sort of antiquated kernel are you using? And even if you are
running something that predates the kernel changes, reserving the
memory in the DT serves the same purpose. Why the custom node
declaring the allocation?

And since your kernel is able to kexec, it obviously knows about the
reservation/pre-programming trick. This hardly makes any sense.

M.

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