linux-kernel - [PATCH v2 2/2] arm64: topology: Use PPTT to determine if PE is a thread

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Message-Id: <20190614223158.49575-3-jeremy.linton@arm.com>
Date:   Fri, 14 Jun 2019 17:31:58 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, will.deacon@....com, rjw@...ysocki.net,
        sudeep.holla@....com, lenb@...nel.org,
        Jeremy Linton <jeremy.linton@....com>
Subject: [PATCH v2 2/2] arm64: topology: Use PPTT to determine if PE is a thread

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@....com>
---
 arch/arm64/kernel/topology.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 0825c4a856e3..cbbedb53cf06 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -346,11 +346,9 @@ void remove_cpu_topology(unsigned int cpu)
  */
 static int __init parse_acpi_topology(void)
 {
-	bool is_threaded;
+	int is_threaded;
 	int cpu, topology_id;
 
-	is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
-
 	for_each_possible_cpu(cpu) {
 		int i, cache_id;
 
@@ -358,6 +356,10 @@ static int __init parse_acpi_topology(void)
 		if (topology_id < 0)
 			return topology_id;
 
+		is_threaded = acpi_pptt_cpu_is_thread(cpu);
+		if (is_threaded < 0)
+			is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
+
 		if (is_threaded) {
 			cpu_topology[cpu].thread_id = topology_id;
 			topology_id = find_acpi_cpu_topology(cpu, 1);
-- 
2.21.0