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Message-ID: <20251118144013.000050c2@huawei.com>
Date: Tue, 18 Nov 2025 14:40:13 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <james.morse@....com>, <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>,
	<jeremy.linton@....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 Mon, 17 Nov 2025 16:59:42 +0000
Ben Horgan <ben.horgan@....com> 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>
Hi Ben,

I'd like the change to land in ACPICA but if it doesn't this might need
a future rework to avoid long term duplication.  For now with the __packed
marking and a few formatting niggles (see inline) tidied up.

Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.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;

Unrelated change..

>  	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);

extra space after =

> +	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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