[PATCH 1/5] powerpc/smp: use cpu_to_chip_id() to find siblings

[Oliver O'Halloran]

To determine which logical CPUs are on the same core the kernel uses the
ibm,chipid property from the device tree node associated with that cpu.
The lookup for this this information is currently open coded in both
traverse_siblings() and traverse_siblings_chip_id(). This patch replaces
these manual lookups with the existing cpu_to_chip_id() function.

Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
 arch/powerpc/kernel/smp.c | 39 +++++++++++++--------------------------
 1 file changed, 13 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 893bd7f79be6..dfe0e1d9cd06 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -613,19 +613,11 @@ 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));
@@ -634,7 +626,6 @@ static void traverse_siblings_chip_id(int cpu, bool add, int chipid)
 				cpumask_clear_cpu(i, cpu_core_mask(cpu));
 			}
 		}
-		of_node_put(np);
 	}
 }
 
@@ -664,23 +655,19 @@ 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 (same die) */
+	chip_id = cpu_to_chip_id(cpu);
+
+	if (chip_id >= 0) {
+		traverse_siblings_chip_id(cpu, add, chip_id);
+		return;
 	}
 
+	/* if the chip-id fails then threads which share L2 cache are */
+
 	l2_cache = cpu_to_l2cache(cpu);
 	mask = add ? cpu_online_mask : cpu_present_mask;
 	for_each_cpu(i, mask) {
-- 
2.9.3