cacheinfo: Allow early detection and population of cache attributes

Some architecture/platforms may need to setup cache properties very
early in the boot along with other cpu topologies so that all these
information can be used to build sched_domains which is used by the
scheduler.

Allow detect_cache_attributes to be called quite early during the boot.

Link: https://lore.kernel.org/r/20220704101605.1318280-7-sudeep.holla@arm.com
Tested-by: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/base/cacheinfo.c

@@ -193,14 +193,8 @@ static int cache_setup_of_node(unsigned int cpu)
 {
 	struct device_node *np;
 	struct cacheinfo *this_leaf;
-	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
 	unsigned int index = 0;
 
-	/* skip if fw_token is already populated */
-	if (this_cpu_ci->info_list->fw_token) {
-		return 0;
-	}
-
 	np = of_cpu_device_node_get(cpu);
 	if (!np) {
 		pr_err("Failed to find cpu%d device node\n", cpu);
@@ -236,6 +230,18 @@ int __weak cache_setup_acpi(unsigned int cpu)
 
 unsigned int coherency_max_size;
 
+static int cache_setup_properties(unsigned int cpu)
+{
+	int ret = 0;
+
+	if (of_have_populated_dt())
+		ret = cache_setup_of_node(cpu);
+	else if (!acpi_disabled)
+		ret = cache_setup_acpi(cpu);
+
+	return ret;
+}
+
 static int cache_shared_cpu_map_setup(unsigned int cpu)
 {
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
@@ -246,21 +252,21 @@ static int cache_shared_cpu_map_setup(unsigned int cpu)
 	if (this_cpu_ci->cpu_map_populated)
 		return 0;
 
-	if (of_have_populated_dt())
+	/*
-		ret = cache_setup_of_node(cpu);
+	 * skip setting up cache properties if LLC is valid, just need
-	else if (!acpi_disabled)
+	 * to update the shared cpu_map if the cache attributes were
-		ret = cache_setup_acpi(cpu);
+	 * populated early before all the cpus are brought online
-
+	 */
-	if (ret)
+	if (!last_level_cache_is_valid(cpu)) {
-		return ret;
+		ret = cache_setup_properties(cpu);
+		if (ret)
+			return ret;
+	}
 
 	for (index = 0; index < cache_leaves(cpu); index++) {
 		unsigned int i;
 
 		this_leaf = per_cpu_cacheinfo_idx(cpu, index);
-		/* skip if shared_cpu_map is already populated */
-		if (!cpumask_empty(&this_leaf->shared_cpu_map))
-			continue;
 
 		cpumask_set_cpu(cpu, &this_leaf->shared_cpu_map);
 		for_each_online_cpu(i) {
@@ -330,17 +336,28 @@ int __weak populate_cache_leaves(unsigned int cpu)
 	return -ENOENT;
 }
 
-static int detect_cache_attributes(unsigned int cpu)
+int detect_cache_attributes(unsigned int cpu)
 {
 	int ret;
 
+	/* Since early detection of the cacheinfo is allowed via this
+	 * function and this also gets called as CPU hotplug callbacks via
+	 * cacheinfo_cpu_online, the initialisation can be skipped and only
+	 * CPU maps can be updated as the CPU online status would be update
+	 * if called via cacheinfo_cpu_online path.
+	 */
+	if (per_cpu_cacheinfo(cpu))
+		goto update_cpu_map;
+
 	if (init_cache_level(cpu) || !cache_leaves(cpu))
 		return -ENOENT;
 
 	per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
 					 sizeof(struct cacheinfo), GFP_KERNEL);
-	if (per_cpu_cacheinfo(cpu) == NULL)
+	if (per_cpu_cacheinfo(cpu) == NULL) {
+		cache_leaves(cpu) = 0;
 		return -ENOMEM;
+	}
 
 	/*
 	 * populate_cache_leaves() may completely setup the cache leaves and
@@ -349,6 +366,8 @@ static int detect_cache_attributes(unsigned int cpu)
 	ret = populate_cache_leaves(cpu);
 	if (ret)
 		goto free_ci;
+
+update_cpu_map:
 	/*
 	 * For systems using DT for cache hierarchy, fw_token
 	 * and shared_cpu_map will be set up here only if they are

include/linux/cacheinfo.h

@@ -84,6 +84,7 @@ int populate_cache_leaves(unsigned int cpu);
 int cache_setup_acpi(unsigned int cpu);
 bool last_level_cache_is_valid(unsigned int cpu);
 bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y);
+int detect_cache_attributes(unsigned int cpu);
 #ifndef CONFIG_ACPI_PPTT
 /*
  * acpi_find_last_cache_level is only called on ACPI enabled