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Subject[PATCH 4.19 70/81] arm64: topology: Use PPTT to determine if PE is a thread
Date
From: Jeremy Linton <jeremy.linton@arm.com>

Commit 98dc19902a0b2e5348e43d6a2c39a0a7d0fc639e upstream.

ACPI 6.3 adds a thread flag to represent if a CPU/PE is
actually a thread. Given that the MPIDR_MT bit may not
represent this information consistently on homogeneous machines
we should prefer the PPTT flag if its available.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Robert Richter <rrichter@marvell.com>
[will: made acpi_cpu_is_threaded() return 'bool']
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/kernel/topology.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 0825c4a856e33..6106c49f84bc8 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -340,17 +340,28 @@ void remove_cpu_topology(unsigned int cpu)
}

#ifdef CONFIG_ACPI
+static bool __init acpi_cpu_is_threaded(int cpu)
+{
+ int is_threaded = acpi_pptt_cpu_is_thread(cpu);
+
+ /*
+ * if the PPTT doesn't have thread information, assume a homogeneous
+ * machine and return the current CPU's thread state.
+ */
+ if (is_threaded < 0)
+ is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
+
+ return !!is_threaded;
+}
+
/*
* Propagate the topology information of the processor_topology_node tree to the
* cpu_topology array.
*/
static int __init parse_acpi_topology(void)
{
- bool is_threaded;
int cpu, topology_id;

- is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
-
for_each_possible_cpu(cpu) {
int i, cache_id;

@@ -358,7 +369,7 @@ static int __init parse_acpi_topology(void)
if (topology_id < 0)
return topology_id;

- if (is_threaded) {
+ if (acpi_cpu_is_threaded(cpu)) {
cpu_topology[cpu].thread_id = topology_id;
topology_id = find_acpi_cpu_topology(cpu, 1);
cpu_topology[cpu].core_id = topology_id;
--
2.20.1


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