[PATCH 1/4] powerpc/smp: Use cpu_to_chip_id() to find core siblings

[Oliver O'Halloran]

When building the CPU scheduler topology the kernel uses the ibm,chipid
property from the devicetree to group logical CPUs. Currently the DT
search for this property is open-coded in smp.c and this functionality
is a duplication of what's in cpu_to_chip_id() already. This patch
removes the existing search in favor of that.

It's worth mentioning that the semantics of the search are different
in cpu_to_chip_id(). When there is no ibm,chipid in the CPUs node it
will also search /cpus and / for the property, but this should not
effect the output topology.

Signed-off-by: Oliver O'Halloran <ooh...@gmail.com>
---
 arch/powerpc/kernel/smp.c | 37 +++++++++++--------------------------
 1 file changed, 11 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index dbcd22e09a2c..40f1f268be83 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -829,19 +829,11 @@ EXPORT_SYMBOL_GPL(cpu_first_thread_of_core);
 
 static void traverse_siblings_chip_id(int cpu, bool add, int chipid)
 {
-       const struct cpumask *mask;
-       struct device_node *np;
-       int i, plen;
-       const __be32 *prop;
+       const struct cpumask *mask = add ? cpu_online_mask : cpu_present_mask;
+       int i;
 
-       mask = add ? cpu_online_mask : cpu_present_mask;
        for_each_cpu(i, mask) {
-               np = of_get_cpu_node(i, NULL);
-               if (!np)
-                       continue;
-               prop = of_get_property(np, "ibm,chip-id", &plen);
-               if (prop && plen == sizeof(int) &&
-                   of_read_number(prop, 1) == chipid) {
+               if (cpu_to_chip_id(i) == chipid) {
                        if (add) {
                                cpumask_set_cpu(cpu, cpu_core_mask(i));
                                cpumask_set_cpu(i, cpu_core_mask(cpu));
@@ -850,7 +842,6 @@ static void traverse_siblings_chip_id(int cpu, bool add, 
int chipid)
                                cpumask_clear_cpu(i, cpu_core_mask(cpu));
                        }
                }
-               of_node_put(np);
        }
 }
 
@@ -880,21 +871,15 @@ static void traverse_core_siblings(int cpu, bool add)
 {
        struct device_node *l2_cache, *np;
        const struct cpumask *mask;
-       int i, chip, plen;
-       const __be32 *prop;
+       int chip_id;
+       int i;
 
-       /* First see if we have ibm,chip-id properties in cpu nodes */
-       np = of_get_cpu_node(cpu, NULL);
-       if (np) {
-               chip = -1;
-               prop = of_get_property(np, "ibm,chip-id", &plen);
-               if (prop && plen == sizeof(int))
-                       chip = of_read_number(prop, 1);
-               of_node_put(np);
-               if (chip >= 0) {
-                       traverse_siblings_chip_id(cpu, add, chip);
-                       return;
-               }
+       /* threads that share a chip-id are considered siblings */
+       chip_id = cpu_to_chip_id(cpu);
+
+       if (chip_id >= 0) {
+               traverse_siblings_chip_id(cpu, add, chip_id);
+               return;
        }
 
        l2_cache = cpu_to_l2cache(cpu);
-- 
2.9.4