1 files changed, 77 insertions, 1 deletions

diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index 4caca71c906f..50e95d894e35 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/arch/arm/common/bL_switcher.c
@@ -289,18 +289,94 @@ int bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
 }
 EXPORT_SYMBOL_GPL(bL_switch_request);
 
+/*
+ * Activation and configuration code.
+ */
+
+static cpumask_t bL_switcher_removed_logical_cpus;
+
+static void __init bL_switcher_restore_cpus(void)
+{
+        int i;
+
+        for_each_cpu(i, &bL_switcher_removed_logical_cpus)
+                cpu_up(i);
+}
+
+static int __init bL_switcher_halve_cpus(void)
+{
+        int cpu, cluster, i, ret;
+        cpumask_t cluster_mask[2], common_mask;
+
+        cpumask_clear(&bL_switcher_removed_logical_cpus);
+        cpumask_clear(&cluster_mask[0]);
+        cpumask_clear(&cluster_mask[1]);
+
+        for_each_online_cpu(i) {
+                cpu = cpu_logical_map(i) & 0xff;
+                cluster = (cpu_logical_map(i) >> 8) & 0xff;
+                if (cluster >= 2) {
+                        pr_err("%s: only dual cluster systems are supported\n", __func__);
+                        return -EINVAL;
+                }
+                cpumask_set_cpu(cpu, &cluster_mask[cluster]);
+        }
+
+        if (!cpumask_and(&common_mask, &cluster_mask[0], &cluster_mask[1])) {
+                pr_err("%s: no common set of CPUs\n", __func__);
+                return -EINVAL;
+        }
+
+        for_each_online_cpu(i) {
+                cpu = cpu_logical_map(i) & 0xff;
+                cluster = (cpu_logical_map(i) >> 8) & 0xff;
+
+                if (cpumask_test_cpu(cpu, &common_mask)) {
+                        /*
+                         * We keep only those logical CPUs which number
+                         * is equal to their physical CPU number. This is
+                         * not perfect but good enough for now.
+                         */
+                        if (cpu == i)
+                                continue;
+                }
+
+                ret = cpu_down(i);
+                if (ret) {
+                        bL_switcher_restore_cpus();
+                        return ret;
+                }
+                cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
+        }
+
+        return 0;
+}
+
 static int __init bL_switcher_init(void)
 {
-        int cpu;
+        int cpu, ret;
 
         pr_info("big.LITTLE switcher initializing\n");
 
+        if (MAX_NR_CLUSTERS != 2) {
+                pr_err("%s: only dual cluster systems are supported\n", __func__);
+                return -EINVAL;
+        }
+
+        cpu_hotplug_driver_lock();
+        ret = bL_switcher_halve_cpus();
+        if (ret) {
+                cpu_hotplug_driver_unlock();
+                return ret;
+        }
+
         for_each_online_cpu(cpu) {
                 struct bL_thread *t = &bL_threads[cpu];
                 init_waitqueue_head(&t->wq);
                 t->wanted_cluster = -1;
                 t->task = bL_switcher_thread_create(cpu, t);
         }
+        cpu_hotplug_driver_unlock();
 
         pr_info("big.LITTLE switcher initialized\n");
         return 0;