linux-kernel - Re: [RFC 1/1] ARM: Drop !ARCH_MULTIPLATFORM dependency from Cortex A8/9 erratas

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Message-ID: <Y5OCTseqVQ+AcMqm@shell.armlinux.org.uk>
Date:   Fri, 9 Dec 2022 18:45:34 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Sebastian Reichel <sebastian.reichel@...labora.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [RFC 1/1] ARM: Drop !ARCH_MULTIPLATFORM dependency from Cortex
 A8/9 erratas

On Fri, Dec 09, 2022 at 07:20:00PM +0100, Sebastian Reichel wrote:
> All the erratas for more recent CPUs (Cortex A15/A12/A17) do not
> require !ARCH_MULTIPLATFORM, since there is runtime detection of
> effected CPUs in arch/arm/mm/proc-v7.S.
> 
> Errata config options for the older Cortex A8/A9 CPUs have the
> !ARCH_MULTIPLATFORM dependency, but the CPUs are also runtime
> detected. Since there is runtime detection, it should be fine
> to enable the erratas for a multi platform kernel.
> 
> Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> ---
> For me the most likely explanation that this has not yet happened is
> me missing an important detail, so I sent it as RFC. If you point it
> out I will try to document the reason.

IIRC, the reason these are marked with !ARCH_MULTIPLATFORM is for when
the kernel is running in the non-secure world - the accessed registers
may prevent platforms booting. However, it was a long time ago and I
don't remember clearly now.

-- 
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