Re: [PATCH] arm64: errata: Enable the AC03_CPU_38 workaround for ampere1a

[Oliver Upton <oliver.upton@linux.dev>]

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@os.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