[PATCH v5 8/9] arm64: topology: Enable ACPI/PPTT based CPU topology.

[Jeremy Linton]

Propagate the topology information from the PPTT tree to the
cpu_topology array. We can get the thread id, core_id and
cluster_id by assuming certain levels of the PPTT tree correspond
to those concepts. The package_id is flagged in the tree and can be
found by calling find_acpi_cpu_topology_package() which terminates
its search when it finds an ACPI node flagged as the physical
package. If the tree doesn't contain enough levels to represent
all of the requested levels then the root node will be returned
for all subsequent levels.

Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
---
 arch/arm64/kernel/topology.c | 47 +++++++++++++++++++++++++++++++++++++++++++-
 include/linux/topology.h     |  2 ++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 74a8a5173a35..198714aca9e8 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -11,6 +11,7 @@
  * for more details.
  */
 
+#include <linux/acpi.h>
 #include <linux/arch_topology.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
@@ -22,6 +23,7 @@
 #include <linux/sched.h>
 #include <linux/sched/topology.h>
 #include <linux/slab.h>
+#include <linux/smp.h>
 #include <linux/string.h>
 
 #include <asm/cpu.h>
@@ -300,6 +302,47 @@ static void __init reset_cpu_topology(void)
 	}
 }
 
+#ifdef CONFIG_ACPI
+/*
+ * Propagate the topology information of the processor_topology_node tree to the
+ * cpu_topology array.
+ */
+static int __init parse_acpi_topology(void)
+{
+	u64 is_threaded;
+	int cpu;
+	int topology_id;
+
+	is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
+
+	for_each_possible_cpu(cpu) {
+		topology_id = find_acpi_cpu_topology(cpu, 0);
+		if (topology_id < 0)
+			return topology_id;
+
+		if (is_threaded) {
+			cpu_topology[cpu].thread_id = topology_id;
+			topology_id = find_acpi_cpu_topology(cpu, 1);
+			cpu_topology[cpu].core_id   = topology_id;
+			topology_id = find_acpi_cpu_topology_package(cpu);
+			cpu_topology[cpu].physical_id = topology_id;
+		} else {
+			cpu_topology[cpu].thread_id  = -1;
+			cpu_topology[cpu].core_id    = topology_id;
+			topology_id = find_acpi_cpu_topology_package(cpu);
+			cpu_topology[cpu].physical_id = topology_id;
+		}
+	}
+	return 0;
+}
+
+#else
+static int __init parse_acpi_topology(void)
+{
+	/*ACPI kernels should be built with PPTT support*/
+	return -EINVAL;
+}
+#endif
 
 void __init init_cpu_topology(void)
 {
@@ -309,6 +352,8 @@ void __init init_cpu_topology(void)
 	 * Discard anything that was parsed if we hit an error so we
 	 * don't use partial information.
 	 */
-	if (of_have_populated_dt() && parse_dt_topology())
+	if ((!acpi_disabled) && parse_acpi_topology())
+		reset_cpu_topology();
+	else if (of_have_populated_dt() && parse_dt_topology())
 		reset_cpu_topology();
 }
diff --git a/include/linux/topology.h b/include/linux/topology.h
index cb0775e1ee4b..170ce87edd88 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -43,6 +43,8 @@
 		if (nr_cpus_node(node))
 
 int arch_update_cpu_topology(void);
+int find_acpi_cpu_topology(unsigned int cpu, int level);
+int find_acpi_cpu_topology_package(unsigned int cpu);
 
 /* Conform to ACPI 2.0 SLIT distance definitions */
 #define LOCAL_DISTANCE		10
-- 
2.13.5