summaryrefslogtreecommitdiff
path: root/drivers/acpi
diff options
context:
space:
mode:
authorJeremy Linton <jeremy.linton@arm.com>2019-06-27 00:37:16 +0300
committerWill Deacon <will@kernel.org>2019-06-27 18:53:18 +0300
commit56855a99f3d0d1e9f1f4e24f5851f9bf14c83296 (patch)
tree32211f461b703b6145dd9348caf70d6aa6d0c6e3 /drivers/acpi
parented2b664fcc8073c09394393756df3fc86977bbac (diff)
downloadlinux-56855a99f3d0d1e9f1f4e24f5851f9bf14c83296.tar.xz
ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens
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: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Hanjun Guo <hanjun.guo@linaro.org> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/pptt.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 05344413f199..1e7ac0bd0d3a 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -683,3 +683,29 @@ 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);
+}