Re: [External] [PATCH RFC v2 13/17] acpi: pptt: Add helper to find a cache from id

[yunhui cui]

Hi Drew,

On Thu, Jan 29, 2026 at 4:28 AM Drew Fustini <fustini@xxxxxxxxxx> wrote:
>
> Add function to find the pointer to an instance of acpi_pptt_cache.
>
> find_acpi_cache_from_id() is based on find_acpi_cache_level_from_id()
> from commit c4170570cc7f ("ACPI / PPTT: Find PPTT cache level by ID") in
> the morse/mpam/snapshot/v6.14-rc1 branch.
>
> TODO: find_acpi_cache_level_from_id() has changed since then so this
> function should be updated. In additon, there may be a simpler way for
> acpi_parse_rqsc() than adding this function to get a pointer to
> acpi_pptt_cache.
>
> Signed-off-by: Drew Fustini <fustini@xxxxxxxxxx>
> ---
>  drivers/acpi/pptt.c  | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h |  8 +++++++
>  2 files changed, 71 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index de5f8c018333..d1002673dc39 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -1063,3 +1063,66 @@ int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus)
>
>         return 0;
>  }
> +
> +/*
> + * find_acpi_cache_from_id() is adapted from find_acpi_cache_level_from_id()
> + * introduced by c4170570cc7f ("ACPI / PPTT: Find PPTT cache level by ID")
> + * in the morse/mpam/snapshot/v6.14-rc1 branch.
> + *
> + * TODO: find_acpi_cache_level_from_id() has changed since then so this
> + * function should be updated. In additon, there may be a simpler way for
> + * acpi_parse_rqsc() than adding this function to get a pointer to
> + * acpi_pptt_cache.
> + */
> +struct acpi_pptt_cache *find_acpi_cache_from_id(u32 cache_id)
> +{
> +       u32 acpi_cpu_id;
> +       acpi_status status;
> +       int level, cpu, num_levels;
> +       struct acpi_pptt_cache *cache;
> +       struct acpi_table_header *table;
> +       struct acpi_pptt_cache_v1 *cache_v1;
> +       struct acpi_pptt_processor *cpu_node;
> +
> +       status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> +       if (ACPI_FAILURE(status)) {
> +               acpi_pptt_warn_missing();
> +               return NULL;
> +       }
> +
> +       if (table->revision < 3) {
> +               acpi_put_table(table);
> +               return NULL;
> +       }
> +
> +       for_each_possible_cpu(cpu) {
> +               num_levels = 0;
> +               acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +
> +               cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> +               if (!cpu_node)
> +                       break;

break or continue?


> +               num_levels = acpi_count_levels(table, cpu_node, NULL);
> +
> +               for (level = 1; level <= num_levels; level++) {
> +                       cache = acpi_find_cache_node(table, acpi_cpu_id,
> +                                                    ACPI_PPTT_CACHE_TYPE_UNIFIED,
> +                                                    level, &cpu_node);
> +                       if (!cache)
> +                               continue;
> +
> +                       cache_v1 = ACPI_ADD_PTR(struct acpi_pptt_cache_v1,
> +                                               cache,
> +                                               sizeof(struct acpi_pptt_cache));
> +
> +                       if (cache->flags & ACPI_PPTT_CACHE_ID_VALID &&
> +                           cache_v1->cache_id == cache_id) {
> +                               acpi_put_table(table);
> +                               return cache;
> +                       }
> +               }
> +       }
> +
> +       acpi_put_table(table);
> +       return NULL;
> +}
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index fbf0c3a65f59..fee6a5059a46 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1546,6 +1546,7 @@ int find_acpi_cpu_topology_package(unsigned int cpu);
>  int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
>  void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus);
>  int find_acpi_cache_level_from_id(u32 cache_id);
> +struct acpi_pptt_cache *find_acpi_cache_from_id(u32 cache_id);
>  int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus);
>  #else
>  static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
> @@ -1570,10 +1571,17 @@ static inline int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
>  }
>  static inline void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id,
>                                                      cpumask_t *cpus) { }
> +
>  static inline int find_acpi_cache_level_from_id(u32 cache_id)
>  {
>         return -ENOENT;
>  }
> +
> +static inline struct acpi_pptt_cache *find_acpi_cache_from_id(u32 cache_id)
> +{
> +       return NULL;
> +}
> +
>  static inline int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id,
>                                                       cpumask_t *cpus)
>  {
>
> --
> 2.43.0
>

Thanks,
Yunhui