[PATCH 1/4] ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens
jeremy.linton at arm.com
Tue Mar 26 15:39:35 PDT 2019
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.
Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
drivers/acpi/pptt.c | 26 ++++++++++++++++++++++++++
include/linux/acpi.h | 5 +++++
2 files changed, 31 insertions(+)
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 065c4fc245d1..472c95ec816b 100644
@@ -660,3 +660,29 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
+ * find_acpi_cpu_topology_hetero_id() - Determine a unique implementation
+ * @cpu: Kernel logical cpu number
+ * Determine a unique heterogeneous ID for the given CPU. CPUs with the same
+ * implementation should have matching IDs. Since this is a tree we can only
+ * detect implementations where the heterogeneous flag is the parent to all
+ * matching cores. AKA if a two socket machine has two different core types
+ * in each socket this will end up being represented as four unique core types
+ * rather than two.
+ * The returned ID 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.
+ * 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,
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index d5dcebd7aad3..1444fb042898 100644
@@ -1309,6 +1309,7 @@ static inline int lpit_read_residency_count_address(u64 *address)
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);
static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
@@ -1319,6 +1320,10 @@ static inline int find_acpi_cpu_topology_package(unsigned int cpu)
+static 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)
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