powerpc: Make core sibling information available to userspace

Implement the notion of "core siblings" for powerpc.  This makes
/sys/devices/system/cpu/cpu*/topology/core_siblings present sensible
values, indicating online CPUs which share an L2 cache.

BenH: Made cpu_to_l2cache() use of_find_node_by_phandle() instead
of IBM-specific open coded search

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 3c4d07e5e06a..f7a2f81b5b7d 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -63,10 +63,12 @@ struct thread_info *secondary_ti;
 cpumask_t cpu_possible_map = CPU_MASK_NONE;
 cpumask_t cpu_online_map = CPU_MASK_NONE;
 DEFINE_PER_CPU(cpumask_t, cpu_sibling_map) = CPU_MASK_NONE;
+DEFINE_PER_CPU(cpumask_t, cpu_core_map) = CPU_MASK_NONE;
 
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL(cpu_possible_map);
 EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);
+EXPORT_PER_CPU_SYMBOL(cpu_core_map);
 
 /* SMP operations for this machine */
 struct smp_ops_t *smp_ops;
@@ -230,6 +232,7 @@ void __devinit smp_prepare_boot_cpu(void)
 
         cpu_set(boot_cpuid, cpu_online_map);
         cpu_set(boot_cpuid, per_cpu(cpu_sibling_map, boot_cpuid));
+        cpu_set(boot_cpuid, per_cpu(cpu_core_map, boot_cpuid));
 #ifdef CONFIG_PPC64
         paca[boot_cpuid].__current = current;
 #endif
@@ -377,11 +380,36 @@ int __cpuinit __cpu_up(unsigned int cpu)
         return 0;
 }
 
+/* Must be called when no change can occur to cpu_present_map,
+ * i.e. during cpu online or offline.
+ */
+static struct device_node *cpu_to_l2cache(int cpu)
+{
+        struct device_node *np;
+        const phandle *php;
+        phandle ph;
+
+        if (!cpu_present(cpu))
+                return NULL;
+
+        np = of_get_cpu_node(cpu, NULL);
+        if (np == NULL)
+                return NULL;
+
+        php = of_get_property(np, "l2-cache", NULL);
+        if (php == NULL)
+                return NULL;
+        ph = *php;
+        of_node_put(np);
+
+        return of_find_node_by_phandle(ph);
+}
 
 /* Activate a secondary processor. */
 int __devinit start_secondary(void *unused)
 {
         unsigned int cpu = smp_processor_id();
+        struct device_node *l2_cache;
         int i, base;
 
         atomic_inc(&init_mm.mm_count);
@@ -410,7 +438,26 @@ int __devinit start_secondary(void *unused)
                         continue;
                 cpu_set(cpu, per_cpu(cpu_sibling_map, base + i));
                 cpu_set(base + i, per_cpu(cpu_sibling_map, cpu));
+
+                /* cpu_core_map should be a superset of
+                 * cpu_sibling_map even if we don't have cache
+                 * information, so update the former here, too.
+                 */
+                cpu_set(cpu, per_cpu(cpu_core_map, base +i));
+                cpu_set(base + i, per_cpu(cpu_core_map, cpu));
         }
+        l2_cache = cpu_to_l2cache(cpu);
+        for_each_online_cpu(i) {
+                struct device_node *np = cpu_to_l2cache(i);
+                if (!np)
+                        continue;
+                if (np == l2_cache) {
+                        cpu_set(cpu, per_cpu(cpu_core_map, i));
+                        cpu_set(i, per_cpu(cpu_core_map, cpu));
+                }
+                of_node_put(np);
+        }
+        of_node_put(l2_cache);
         ipi_call_unlock();
 
         local_irq_enable();
@@ -448,6 +495,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 #ifdef CONFIG_HOTPLUG_CPU
 int __cpu_disable(void)
 {
+        struct device_node *l2_cache;
         int cpu = smp_processor_id();
         int base, i;
         int err;
@@ -464,7 +512,23 @@ int __cpu_disable(void)
         for (i = 0; i < threads_per_core; i++) {
                 cpu_clear(cpu, per_cpu(cpu_sibling_map, base + i));
                 cpu_clear(base + i, per_cpu(cpu_sibling_map, cpu));
+                cpu_clear(cpu, per_cpu(cpu_core_map, base +i));
+                cpu_clear(base + i, per_cpu(cpu_core_map, cpu));
+        }
+
+        l2_cache = cpu_to_l2cache(cpu);
+        for_each_present_cpu(i) {
+                struct device_node *np = cpu_to_l2cache(i);
+                if (!np)
+                        continue;
+                if (np == l2_cache) {
+                        cpu_clear(cpu, per_cpu(cpu_core_map, i));
+                        cpu_clear(i, per_cpu(cpu_core_map, cpu));
+                }
+                of_node_put(np);
         }
+        of_node_put(l2_cache);
+
 
         return 0;
 }