powerpc: Use ibm, chip-id property to compute cpu_core_mask if available

Some systems have an ibm,chip-id property in the cpu nodes in the
device tree.  On these systems, we now use that to compute the
cpu_core_mask (i.e. the set of core siblings) rather than looking
at cache properties.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Tested-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 45 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 0cc69d5deac9..009900dd8f25 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -609,6 +609,33 @@ int cpu_first_thread_of_core(int core)
 }
 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;
+
+        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 (add) {
+                                cpumask_set_cpu(cpu, cpu_core_mask(i));
+                                cpumask_set_cpu(i, cpu_core_mask(cpu));
+                        } else {
+                                cpumask_clear_cpu(cpu, cpu_core_mask(i));
+                                cpumask_clear_cpu(i, cpu_core_mask(cpu));
+                        }
+                }
+                of_node_put(np);
+        }
+}
+
 /* Must be called when no change can occur to cpu_present_mask,
  * i.e. during cpu online or offline.
  */
@@ -633,14 +660,29 @@ static struct device_node *cpu_to_l2cache(int cpu)
 
 static void traverse_core_siblings(int cpu, bool add)
 {
-        struct device_node *l2_cache;
+        struct device_node *l2_cache, *np;
         const struct cpumask *mask;
-        int i;
+        int i, chip, plen;
+        const __be32 *prop;
+
+        /* 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;
+                }
+        }
 
         l2_cache = cpu_to_l2cache(cpu);
         mask = add ? cpu_online_mask : cpu_present_mask;
         for_each_cpu(i, mask) {
-                struct device_node *np = cpu_to_l2cache(i);
+                np = cpu_to_l2cache(i);
                 if (!np)
                         continue;
                 if (np == l2_cache) {