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Message-ID: <5926591f-81aa-4953-9d80-bc85d3ce754f@arm.com>
Date: Wed, 19 Nov 2025 10:28:57 -0600
From: Jeremy Linton <jeremy.linton@....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,
dave.martin@....com, david@...hat.com, dfustini@...libre.com,
fenghuay@...dia.com, gregkh@...uxfoundation.org, gshan@...hat.com,
guohanjun@...wei.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,
rafael@...nel.org, robh@...nel.org, rohit.mathew@....com,
scott@...amperecomputing.com, sdonthineni@...dia.com, sudeep.holla@....com,
tan.shaopeng@...itsu.com, will@...nel.org, xhao@...ux.alibaba.com
Subject: Re: [PATCH v5 03/34] ACPI / PPTT: Add acpi_pptt_cache_v1_full to use
pptt cache as one structure
On 11/17/25 10:59 AM, 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.
To me, reading the code its a lot clearer that there is a version
difference in the subtable this way.
Reviewed-by: Jeremy Linton <jeremy.linton@....com>
>
> 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;
> +};
> +
> static struct acpi_subtable_header *fetch_pptt_subtable(struct acpi_table_header *table_hdr,
> u32 pptt_ref)
> {
> @@ -56,6 +75,18 @@ static struct acpi_pptt_cache *fetch_pptt_cache(struct acpi_table_header *table_
> return (struct acpi_pptt_cache *)fetch_pptt_subtable(table_hdr, pptt_ref);
> }
>
> +static struct acpi_pptt_cache_v1_full *upgrade_pptt_cache(struct acpi_pptt_cache *cache)
> +{
> + if (cache->header.length < sizeof(struct acpi_pptt_cache_v1_full))
> + return NULL;
> +
> + /* No use for v1 if the only additional field is invalid */
> + if (!(cache->flags & ACPI_PPTT_CACHE_ID_VALID))
> + return NULL;
> +
> + return (struct acpi_pptt_cache_v1_full *)cache;
> +}
> +
> static struct acpi_subtable_header *acpi_get_pptt_resource(struct acpi_table_header *table_hdr,
> struct acpi_pptt_processor *node,
> int resource)
> @@ -111,7 +142,7 @@ static unsigned int acpi_pptt_walk_cache(struct acpi_table_header *table_hdr,
> if (res->type != ACPI_PPTT_TYPE_CACHE)
> return 0;
>
> - cache = (struct acpi_pptt_cache *) res;
> + cache = (struct acpi_pptt_cache *)res;
> while (cache) {
> local_level++;
>
> @@ -355,7 +386,6 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *ta
> * @this_leaf: Kernel cache info structure being updated
> * @found_cache: The PPTT node describing this cache instance
> * @cpu_node: A unique reference to describe this cache instance
> - * @revision: The revision of the PPTT table
> *
> * The ACPI spec implies that the fields in the cache structures are used to
> * extend and correct the information probed from the hardware. Lets only
> @@ -365,10 +395,9 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *ta
> */
> static void update_cache_properties(struct cacheinfo *this_leaf,
> struct acpi_pptt_cache *found_cache,
> - struct acpi_pptt_processor *cpu_node,
> - u8 revision)
> + struct acpi_pptt_processor *cpu_node)
> {
> - struct acpi_pptt_cache_v1* found_cache_v1;
> + struct acpi_pptt_cache_v1_full *found_cache_v1;
>
> this_leaf->fw_token = cpu_node;
> if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
> @@ -418,9 +447,8 @@ static void update_cache_properties(struct cacheinfo *this_leaf,
> found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID)
> this_leaf->type = CACHE_TYPE_UNIFIED;
>
> - if (revision >= 3 && (found_cache->flags & ACPI_PPTT_CACHE_ID_VALID)) {
> - found_cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> - found_cache, sizeof(struct acpi_pptt_cache));
> + found_cache_v1 = upgrade_pptt_cache(found_cache);
> + if (found_cache_v1) {
> this_leaf->id = found_cache_v1->cache_id;
> this_leaf->attributes |= CACHE_ID;
> }
> @@ -445,8 +473,7 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
> pr_debug("found = %p %p\n", found_cache, cpu_node);
> if (found_cache)
> update_cache_properties(this_leaf, found_cache,
> - ACPI_TO_POINTER(ACPI_PTR_DIFF(cpu_node, table)),
> - table->revision);
> + ACPI_TO_POINTER(ACPI_PTR_DIFF(cpu_node, table)));
>
> index++;
> }
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