Currently, the LoongArch CPU topology initialization code calculates
each core's package ID by dividing its physical ID by
loongson_sysconf.cores_per_package. This relies on the assumption that
cores_per_package counts in the same domain as physical IDs.

On Loongson 3B6000 (XB612B0V_1.2), cores_per_package matches the visible
core count -- 24 in this case. However, the physical IDs range from 0 to
31 in a noncontinuous fashion:

        $ cat /proc/cpuinfo | grep -i -F 'global_id'
        global_id               : 0
        global_id               : 1
        global_id               : 4
        global_id               : 5
        global_id               : 6
        global_id               : 7
        global_id               : 8
        global_id               : 9
        global_id               : 10
        global_id               : 11
        global_id               : 14
        global_id               : 15
        global_id               : 16
        global_id               : 17
        global_id               : 20
        global_id               : 21
        global_id               : 22
        global_id               : 23
        global_id               : 26
        global_id               : 27
        global_id               : 28
        global_id               : 29
        global_id               : 30
        global_id               : 31

Retrieve the exact package ID from ACPI PPTT when available, in the same
style as retrieving the core ID and thread ID in parse_acpi_topology().
Use this information in loongson_init_secondary() when PPTT readout is
successful. The original division logic is kept as a fallback.

Meanwhile, since some code paths like loongson3_cpufreq expect a
continuous integer sequence of package IDs in [0, MAX_PACKAGES) when
retrieving from cpu_data[], we also canonicalize the package ID to be
filled in parse_acpi_topology() to meet such an expectation.

Cc: stable@vger.kernel.org
Co-developed-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Rong Bao <rong.bao@csmantle.top>
---

v1 -> v2:
- Addressed and incorporated package ID canonicalization code suggested
  by Ruoyao
- Rebased onto present master

v1: https://lore.kernel.org/loongarch/e18efdbb.AXMAAIuqLC8AAAAAAAAAA-ma1qEAAYKJPtkAAAAAADNVAQBpc5ot@mailjet.com/

---
 arch/loongarch/kernel/acpi.c | 28 +++++++++++++++++++++++++++-
 arch/loongarch/kernel/smp.c  |  2 +-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/loongarch/kernel/acpi.c b/arch/loongarch/kernel/acpi.c
index 8f650c9ffecdecdac6bcb324123e222bd04dbcf2..9ad25c642dbc50485ad54a02ed818a34e639f219 100644
--- a/arch/loongarch/kernel/acpi.c
+++ b/arch/loongarch/kernel/acpi.c
@@ -202,9 +202,12 @@ static void __init acpi_process_madt(void)
 
 int pptt_enabled;
 
+static int acpi_package_ids[MAX_PACKAGES];
+static int acpi_nr_packages;
+
 int __init parse_acpi_topology(void)
 {
-	int cpu, topology_id;
+	int cpu, topology_id, i;
 
 	for_each_possible_cpu(cpu) {
 		topology_id = find_acpi_cpu_topology(cpu, 0);
@@ -222,6 +225,29 @@ int __init parse_acpi_topology(void)
 
 			cpu_data[cpu].core = topology_id;
 		}
+
+		topology_id = find_acpi_cpu_topology_package(cpu);
+		if (topology_id < 0) {
+			pr_warn("Invalid BIOS PPTT\n");
+			return -ENOENT;
+		}
+
+		for (i = 0; i < acpi_nr_packages; i++)
+			if (acpi_package_ids[i] == topology_id)
+				break;
+
+		if (i == acpi_nr_packages)
+			acpi_package_ids[acpi_nr_packages++] = topology_id;
+
+		cpu_data[cpu].package = topology_id;
+	}
+
+	for_each_possible_cpu(cpu) {
+		for (int i = 0; i < acpi_nr_packages; i++)
+			if (cpu_data[cpu].package == acpi_package_ids[i]) {
+				cpu_data[cpu].package = i;
+				break;
+			}
 	}
 
 	pptt_enabled = 1;
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 5d792256bbb99a41d0032add6b5ffacffb20b684..9d148b6e41b488daca71a970e1b75cc18638d564 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -426,7 +426,7 @@ void loongson_init_secondary(void)
 	numa_add_cpu(cpu);
 #endif
 	per_cpu(cpu_state, cpu) = CPU_ONLINE;
-	cpu_data[cpu].package =
+	cpu_data[cpu].package = pptt_enabled ? cpu_data[cpu].package :
 		     cpu_logical_map(cpu) / loongson_sysconf.cores_per_package;
 	cpu_data[cpu].core = pptt_enabled ? cpu_data[cpu].core :
 		     cpu_logical_map(cpu) % loongson_sysconf.cores_per_package;

base-commit: 87320be9f0d24fce67631b7eef919f0b79c3e45c
-- 
2.54.0