@@ -910,3 +910,76 @@ int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
ACPI_PPTT_ACPI_IDENTICAL);
}
+
+/**
+ * find_acpi_cache_level_from_id() - Get the level of the specified cache
+ * @cache_id: The id field of the unified cache
+ *
+ * Determine the level relative to any CPU for the unified cache identified by
+ * cache_id. This allows the property to be found even if the CPUs are offline.
+ *
+ * The returned level can be used to group unified caches that are peers.
+ *
+ * The PPTT table must be rev 3 or later,
+ *
+ * If one CPUs L2 is shared with another as L3, this function will return
+ * an unpredictable value.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, or the cache cannot be found.
+ * Otherwise returns a value which represents the level of the specified cache.
+ */
+int find_acpi_cache_level_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 -ENOENT;
+ }
+
+ if (table->revision < 3) {
+ acpi_put_table(table);
+ return -ENOENT;
+ }
+
+ /*
+ * If we found the cache first, we'd still need to walk from each CPU
+ * to find the level...
+ */
+ for_each_possible_cpu(cpu) {
+ acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+ cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
+ if (!cpu_node)
+ break;
+ acpi_count_levels(table, cpu_node, &num_levels, NULL);
+
+ /* Start at 1 for L1 */
+ 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 level;
+ }
+ }
+ }
+
+ acpi_put_table(table);
+ return -ENOENT;
+}
@@ -1542,6 +1542,7 @@ int find_acpi_cpu_topology_cluster(unsigned int cpu);
int find_acpi_cpu_topology_package(unsigned int cpu);
int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
int acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus);
+int find_acpi_cache_level_from_id(u32 cache_id);
#else
static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
{
@@ -1568,6 +1569,10 @@ static inline int acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id,
{
return -EINVAL;
}
+static inline int find_acpi_cache_level_from_id(u32 cache_id)
+{
+ return -EINVAL;
+}
#endif
void acpi_arch_init(void);
The MPAM table identifies caches by id. The MPAM driver also wants to know the cache level to determine if the platform is of the shape that can be managed via resctrl. Cacheinfo has this information, but only for CPUs that are online. Waiting for all CPUs to come online is a problem for platforms where CPUs are brought online late by user-space. Add a helper that walks every possible cache, until it finds the one identified by cache-id, then return the level. acpi_count_levels() expects its levels parameter to be initialised to zero as it passes it to acpi_find_cache_level() as starting_level. The existing callers do this. Document it. Signed-off-by: James Morse <james.morse@arm.com> --- drivers/acpi/pptt.c | 73 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/acpi.h | 5 +++ 2 files changed, 78 insertions(+)