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 passing an arbitrary large level to setup_acpi_cpu_topology()
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 thread/core/cod/package then the package
id will be used for the missing levels.
Since arm64 machines can have 3 distinct topology levels, and the
scheduler only handles sockets/threads well today, we compromise
by collapsing into one of three diffrent configurations. These are
thread/socket, thread/cluster or cluster/socket depending on whether
the machine has threading and multisocket, threading in a single
socket, or doesn't have threading.
This code is loosely based on a combination of code from:
Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
John Garry <john.garry@xxxxxxxxxx>
Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
arch/arm64/kernel/topology.c | 68 +++++++++++++++++++++++++++++++++++++++++++-
include/linux/topology.h | 2 ++
2 files changed, 69 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 9147e5b6326d..8ee5cc5ba9bd 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>
@@ -304,6 +306,68 @@ 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 is_multisocket;
+ int cpu;
+ int topology_id;
+ /* set a large depth, to hit ACPI_PPTT_PHYSICAL_PACKAGE if one exists */
+ const int max_topo = 0xFF;
+
+ is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
+ is_multisocket = acpi_multisocket_count();
+ if (is_multisocket < 0)
+ return is_multisocket;
+
+ for_each_possible_cpu(cpu) {
+ topology_id = setup_acpi_cpu_topology(cpu, 0);
+ if (topology_id < 0)
+ return topology_id;
+
+ if ((is_threaded) && (is_multisocket > 1)) {
+ /* MT per core, and multiple sockets */
+ cpu_topology[cpu].thread_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, 1);
+ cpu_topology[cpu].core_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, 2);
+ cpu_topology[cpu].cluster_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, max_topo);
+ cpu_topology[cpu].package_id = topology_id;
+ } else if (is_threaded) {
+ /* mutltiple threads, but only a single socket */
+ cpu_topology[cpu].thread_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, 1);
+ cpu_topology[cpu].core_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, 2);
+ cpu_topology[cpu].cluster_id = topology_id;
+ cpu_topology[cpu].package_id = topology_id;
+ } else {
+ /* no threads, clusters behave like threads */
+ cpu_topology[cpu].thread_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, 1);
+ cpu_topology[cpu].core_id = topology_id;
+ cpu_topology[cpu].cluster_id = topology_id;
+ topology_id = setup_acpi_cpu_topology(cpu, max_topo);
+ cpu_topology[cpu].package_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)
{
reset_cpu_topology();
@@ -312,6 +376,8 @@ 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 4660749a7303..08bf736be7c1 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 setup_acpi_cpu_topology(unsigned int cpu, int level);
+int acpi_multisocket_count(void);
/* Conform to ACPI 2.0 SLIT distance definitions */
#define LOCAL_DISTANCE 10
--
2.13.5
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