cacheinfo: Add support to check if last level cache(LLC) is valid or shared

It is useful to have helper to check if the given two CPUs share last
level cache. We can do that check by comparing fw_token or by comparing
the cache ID. Currently we check just for fw_token as the cache ID is
optional.

This helper can be used to build the llc_sibling during arch specific
topology parsing and feeding information to the sched_domains. This also
helps to get rid of llc_id in the CPU topology as it is sort of duplicate
information.

Also add helper to check if the llc information in cacheinfo is valid
or not.

Link: https://lore.kernel.org/r/20220704101605.1318280-6-sudeep.holla@arm.comTested-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

@@ -47,6 +47,32 @@ static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
 	return sib_leaf->fw_token == this_leaf->fw_token;
 }
 
+bool last_level_cache_is_valid(unsigned int cpu)
+{
+	struct cacheinfo *llc;
+
+	if (!cache_leaves(cpu))
+		return false;
+
+	llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1);
+
+	return !!llc->fw_token;
+}
+
+bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y)
+{
+	struct cacheinfo *llc_x, *llc_y;
+
+	if (!last_level_cache_is_valid(cpu_x) ||
+	    !last_level_cache_is_valid(cpu_y))
+		return false;
+
+	llc_x = per_cpu_cacheinfo_idx(cpu_x, cache_leaves(cpu_x) - 1);
+	llc_y = per_cpu_cacheinfo_idx(cpu_y, cache_leaves(cpu_y) - 1);
+
+	return cache_leaves_are_shared(llc_x, llc_y);
+}
+
 #ifdef CONFIG_OF
 /* OF properties to query for a given cache type */
 struct cache_type_info {

include/linux/cacheinfo.h

@@ -82,6 +82,8 @@ struct cpu_cacheinfo *get_cpu_cacheinfo(unsigned int cpu);
 int init_cache_level(unsigned int cpu);
 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);
 #ifndef CONFIG_ACPI_PPTT
 /*
  * acpi_find_last_cache_level is only called on ACPI enabled