ACPI / PPTT: Find PPTT cache level by ID

ANBZ: #1644

cherry-picked from https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git

The MPAM table identifies caches by id, but the driver also wants to know
the cache level, without having to wait for whichever core has that cache
to come online.

Add a helper that walks every possible cache, until it finds the one
identified by id, then return the level.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: Shawn Wang <shawnwang@linux.alibaba.com>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

drivers/acpi/pptt.c

@@ -1010,3 +1010,76 @@ 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
+ * and 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;
+		num_levels = acpi_count_levels(table, cpu_node);
+
+		for (level = 0; 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;
+}

include/linux/acpi.h

@@ -1362,6 +1362,7 @@ int find_acpi_cpu_topology(unsigned int cpu, int level);
 int find_acpi_cpu_topology_package(unsigned int cpu);
 int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
 int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
+int find_acpi_cache_level_from_id(u32 cache_id);
 u32 acpi_pptt_count_containers(void);
 int acpi_pptt_for_each_container(acpi_pptt_cpu_callback_t callback, void *arg);
 void acpi_pptt_get_child_cpus(struct acpi_pptt_processor *parent_node, cpumask_t *cpus);
@@ -1390,6 +1391,10 @@ static inline u32 acpi_pptt_count_containers(void)
 {
 	return 0;
 }
+static inline int find_acpi_cache_level_from_id(u32 cache_id)
+{
+	return -EINVAL;
+}
 static inline int
 acpi_pptt_for_each_container(acpi_pptt_cpu_callback_t *callback, void *arg)
 {