ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens

to #25688970

commit 56855a99f3d0d1e9f1f4e24f5851f9bf14c83296 upstream

ACPI 6.3 adds a flag to indicate that child nodes are all
identical cores. This is useful to authoritatively determine
if a set of (possibly offline) cores are identical or not.

Since the flag doesn't give us a unique id we can generate
one and use it to create bitmaps of sibling nodes, or simply
in a loop to determine if a subset of cores are identical.
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: NHanjun Guo <hanjun.guo@linaro.org>
Reviewed-by: NSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: NJeremy Linton <jeremy.linton@arm.com>
Signed-off-by: NWill Deacon <will@kernel.org>
Signed-off-by: Nluanshi <zhangliguang@linux.alibaba.com>
Acked-by: Nzou cao <zoucao@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

drivers/acpi/pptt.c

@@ -735,3 +735,29 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
 	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
 					  ACPI_PPTT_PHYSICAL_PACKAGE);
 }
+
+/**
+ * find_acpi_cpu_topology_hetero_id() - Get a core architecture tag
+ * @cpu: Kernel logical CPU number
+ *
+ * Determine a unique heterogeneous tag for the given CPU. CPUs with the same
+ * implementation should have matching tags.
+ *
+ * The returned tag can be used to group peers with identical implementation.
+ *
+ * The search terminates when a level is found with the identical implementation
+ * flag set or we reach a root node.
+ *
+ * Due to limitations in the PPTT data structure, there may be rare situations
+ * where two cores in a heterogeneous machine may be identical, but won't have
+ * the same tag.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, or the CPU cannot be found.
+ * Otherwise returns a value which represents a group of identical cores
+ * similar to this CPU.
+ */
+int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
+{
+	return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
+					  ACPI_PPTT_ACPI_IDENTICAL);
+}

include/linux/acpi.h

@@ -1303,6 +1303,7 @@ static inline int lpit_read_residency_count_address(u64 *address)
 int acpi_pptt_cpu_is_thread(unsigned int cpu);
 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);
 #else
 static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
@@ -1317,6 +1318,10 @@ static inline int find_acpi_cpu_topology_package(unsigned int cpu)
 {
 	return -EINVAL;
 }
+static inline int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
+{
+	return -EINVAL;
+}
 static inline int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
 {
 	return -EINVAL;