linux-kernel - Re: [PATCH] arm64: errata: Enable the AC03_CPU

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Message-ID: <Zs0OelXKn_-6jtqN@linux.dev>
Date: Mon, 26 Aug 2024 16:23:38 -0700
From: Oliver Upton <oliver.upton@...ux.dev>
To: D Scott Phillips <scott@...amperecomputing.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>,
	Anshuman Khandual <anshuman.khandual@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	Besar Wicaksono <bwicaksono@...dia.com>,
	Easwar Hariharan <eahariha@...ux.microsoft.com>,
	Rob Herring <robh@...nel.org>,
	Andre Przywara <andre.przywara@....com>,
	linux-kernel@...r.kernel.org, patches@...erecomputing.com
Subject: Re: [PATCH] arm64: errata: Enable the AC03_CPU_38 workaround for
 ampere1a

Hi D Scott,

On Mon, Aug 26, 2024 at 02:59:33PM -0700, D Scott Phillips wrote:
> The ampere1a cpu is affected by erratum AC04_CPU_10 which is the same
> bug as AC03_CPU38. Add ampere1a to the AC03_CPU_38 workaround midr list.
> 
> Signed-off-by: D Scott Phillips <scott@...amperecomputing.com>
> ---
>  Documentation/arch/arm64/silicon-errata.rst | 2 ++
>  arch/arm64/Kconfig                          | 2 +-
>  arch/arm64/include/asm/cputype.h            | 2 ++
>  arch/arm64/kernel/cpu_errata.c              | 1 +
>  4 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
> index 50327c05be8d1..39c52385f11fb 100644
> --- a/Documentation/arch/arm64/silicon-errata.rst
> +++ b/Documentation/arch/arm64/silicon-errata.rst
> @@ -55,6 +55,8 @@ stable kernels.
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Ampere         | AmpereOne       | AC03_CPU_38     | AMPERE_ERRATUM_AC03_CPU_38  |
>  +----------------+-----------------+-----------------+-----------------------------+
> +| Ampere         | AmpereOne AC04  | AC04_CPU_10     | AMPERE_ERRATUM_AC03_CPU_38  |
> ++----------------+-----------------+-----------------+-----------------------------+

We tend to stick the marketing term for a part in the second column so
it is more recognizable for the user. Is this a placeholder for something
different from "ampere1a"?

> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index f6b6b45073571..748aa536446ae 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -773,6 +773,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>  		.desc = "AmpereOne erratum AC03_CPU_38",
>  		.capability = ARM64_WORKAROUND_AMPERE_AC03_CPU_38,
>  		ERRATA_MIDR_ALL_VERSIONS(MIDR_AMPERE1),
> +		ERRATA_MIDR_ALL_VERSIONS(MIDR_AMPERE1A),

This will break the workaround on AC03, since the second macro reassigns
::midr_range.

You'll want to use ERRATA_MIDR_RANGE_LIST() instead w/ an array of
affected MIDRs.

-- 
Thanks,
Oliver