Re: [PATCH u-boot-mvebu 2/3] arm: mvebu: a37xx: Map CCI-400 and AP BootROM address space

["Marek Behún" <marek.behun@nic.cz>]

On Tue, 15 Feb 2022 00:28:34 +0100
Pali Rohár <pali@kernel.org> wrote:

> In function build_mem_map() prepares also mapping for CCI-400 and
                            * prepare
> AP BootROM address space.
> 
> A53 AP BootROM by default starts at address 0xfff00000 and is 16 kB long.

RVBAR_EL3 register has value 0xffff0000. The BootROM is 16 KiB long but
the window is 1 MiB long, so the content repeats every 4 KiB.

> CCI-400 in new TF-A version starts at address 0xfe000000 and is 64 kB long.
> 
> Physical addresses are read directly from mvebu registers, so if TF-A
> remaps it in future then it would not cause any issue.

As we talked about in private conversation, I still don't think we
should do this unless it is needed.

CCI may be needed to be mapped if ever there is some driver that needs
to interact with it.

BootROM is never needed by the U-Boot code.

I really don't think that we should map these in production U-Boot
binaries for everyone, when the intention is "for debugging
purposes only". In the last 4 years there were 2 people (me, and you
:)) who were interested in BootROM. In the next 10 years there will be
maybe 2 more. So I really don't think the windows should be mapped for
everyone.

Maybe you can map them if some debug option is enabled in menuconfig?

Marek