linux-kernel - [Question] vendor-specific cpu enable-method

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Date:   Thu, 13 Sep 2018 10:23:35 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [Question] vendor-specific cpu enable-method

Hello.

Sorry if I am asking a stupid question.

For arm64, there are only 2 cpu methods, psci and spin-table.

Why do we still allow vendor-specific methods upstreamed
for arm 32bit ports?

To me, it looks like SoC vendors continue inventing
different (but similar) ways to do the same thing.

It is a historical reason for old platforms.

However, if I look at Documentation/devicetree/bindings/arm/cpus.txt
enable-method properties are still increasing.

psci is available in arch/arm/kernel/psci_smp.c,
but not all SoCs support the security extension.
Is there a simpler one like spin-table available for arm32?

If we force generic methods like psci or spin-table
for new platforms, we can stop proliferated smp code.
(Of course, we are just shifting the complexity
from the kernel to firmware.)

Am I missing something?

-- 
Best Regards
Masahiro Yamada