1 files changed, 66 insertions, 0 deletions
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index ef39b176dc00..da49b56a1ef2 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -932,3 +932,69 @@ void acpi_pptt_get_cpus_from_container(u32 acpi_cpu_id, cpumask_t *cpus)
 				     entry->length);
 	}
 }
+
+/**
+ * find_acpi_cache_level_from_id() - Get the level of the specified cache
+ * @cache_id: The id field of the cache
+ *
+ * Determine the level relative to any CPU for the 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 caches that are peers.
+ *
+ * The PPTT table must be rev 3 or later.
+ *
+ * If one CPU's L2 is shared with another CPU as L3, this function will return
+ * an unpredictable value.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, the revision isn't supported 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)
+{
+	int cpu;
+	struct acpi_table_header *table;
+
+	table = acpi_get_pptt();
+	if (!table)
+		return -ENOENT;
+
+	if (table->revision < 3)
+		return -ENOENT;
+
+	for_each_possible_cpu(cpu) {
+		bool empty;
+		int level = 1;
+		u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+		struct acpi_pptt_cache *cache;
+		struct acpi_pptt_processor *cpu_node;
+
+		cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
+		if (!cpu_node)
+			continue;
+
+		do {
+			int cache_type[] = {CACHE_TYPE_INST, CACHE_TYPE_DATA, CACHE_TYPE_UNIFIED};
+
+			empty = true;
+			for (int i = 0; i < ARRAY_SIZE(cache_type); i++) {
+				struct acpi_pptt_cache_v1_full *cache_v1;
+
+				cache = acpi_find_cache_node(table, acpi_cpu_id, cache_type[i],
+							     level, &cpu_node);
+				if (!cache)
+					continue;
+
+				empty = false;
+
+				cache_v1 = upgrade_pptt_cache(cache);
+				if (cache_v1 && cache_v1->cache_id == cache_id)
+					return level;
+			}
+			level++;
+		} while (!empty);
+	}
+
+	return -ENOENT;
+}