linux-kernel - Re: [PATCH v5 03/34] ACPI / PPTT: Add acpi_pptt_cache_v1

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Message-ID: <88795f32-bfb7-4bec-b1fb-752b3e72ffbb@nvidia.com>
Date: Mon, 17 Nov 2025 20:03:34 -0800
From: Fenghua Yu <fenghuay@...dia.com>
To: Ben Horgan <ben.horgan@....com>, james.morse@....com
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
 baolin.wang@...ux.alibaba.com, bobo.shaobowang@...wei.com,
 carl@...amperecomputing.com, catalin.marinas@....com, dakr@...nel.org,
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 jeremy.linton@....com, jonathan.cameron@...wei.com, kobak@...dia.com,
 lcherian@...vell.com, lenb@...nel.org, linux-acpi@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 lpieralisi@...nel.org, peternewman@...gle.com, quic_jiles@...cinc.com,
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Subject: Re: [PATCH v5 03/34] ACPI / PPTT: Add acpi_pptt_cache_v1_full to use
 pptt cache as one structure

Hi, Ben,

On 11/17/25 08:59, Ben Horgan wrote:
> In actbl2.h, acpi_pptt_cache describes the fields in the original
> Cache Type Structure. In PPTT table version 3 a new field was added at the
> end, cache_id. This is described in acpi_pptt_cache_v1 but rather than
> including all v1 fields it just includes this one.
> 
> In lieu of this being fixed in acpica, introduce acpi_pptt_cache_v1_full to
> contain all the fields of the Cache Type Structure . Update the existing
> code to use this new struct. This simplifies the code and removes a
> non-standard use of ACPI_ADD_PTR.
> 
> Signed-off-by: Ben Horgan <ben.horgan@....com>
> ---
> I have opened a pull request to acpica to update acpi_pptt_cache_v1 to
> include all fields. https://github.com/acpica/acpica/pull/1059
> 
> Change since v4:
> Use fields directly in acpi_pptt_cache_v1_full
> Delay the casting
> 
> Changes since v3:
> New patch
> ---
>   drivers/acpi/pptt.c | 47 +++++++++++++++++++++++++++++++++++----------
>   1 file changed, 37 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 2856254e29d7..53fde9bd8140 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -21,6 +21,25 @@
>   #include <linux/cacheinfo.h>
>   #include <acpi/processor.h>
>   
> +/*
> + * The acpi_pptt_cache_v1 in actbl2.h, which is imported from acpica,
> + * only contains the cache_id field rather than all the fields of the
> + * Cache Type Structure. Use this alternative structure until it is
> + * resolved in acpica.
> + */
> +struct acpi_pptt_cache_v1_full {
> +	struct acpi_subtable_header header;
> +	u16 reserved;
> +	u32 flags;
> +	u32 next_level_of_cache;
> +	u32 size;
> +	u32 number_of_sets;
> +	u8 associativity;
> +	u8 attributes;
> +	u16 line_size;
> +	u32 cache_id;
> +};

Should "__packed" be added to this table?

Should this table be defined in include/acpi/actbl2.h? Seems defining 
the two cache tables separately in two places are not natural?

Thanks.

-Fenghua