2 files changed, 75 insertions, 12 deletions

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 8200deaa14f6..28d2be00ed89 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -126,6 +126,75 @@ void store_cpu_topology(unsigned int cpuid)
 		cpu_topology[cpuid].socket_id, mpidr);
 }
 
+
+#ifdef CONFIG_SCHED_HMP
+
+static const char * const little_cores[] = {
+	"arm,cortex-a7",
+	NULL,
+};
+
+static bool is_little_cpu(struct device_node *cn)
+{
+	const char * const *lc;
+	for (lc = little_cores; *lc; lc++)
+		if (of_device_is_compatible(cn, *lc))
+			return true;
+	return false;
+}
+
+void __init arch_get_fast_and_slow_cpus(struct cpumask *fast,
+					struct cpumask *slow)
+{
+	struct device_node *cn = NULL;
+	int cpu = 0;
+
+	cpumask_clear(fast);
+	cpumask_clear(slow);
+
+	/*
+	 * Use the config options if they are given. This helps testing
+	 * HMP scheduling on systems without a big.LITTLE architecture.
+	 */
+	if (strlen(CONFIG_HMP_FAST_CPU_MASK) && strlen(CONFIG_HMP_SLOW_CPU_MASK)) {
+		if (cpulist_parse(CONFIG_HMP_FAST_CPU_MASK, fast))
+			WARN(1, "Failed to parse HMP fast cpu mask!\n");
+		if (cpulist_parse(CONFIG_HMP_SLOW_CPU_MASK, slow))
+			WARN(1, "Failed to parse HMP slow cpu mask!\n");
+		return;
+	}
+
+	/*
+	 * Else, parse device tree for little cores.
+	 */
+	while ((cn = of_find_node_by_type(cn, "cpu"))) {
+
+		if (cpu >= num_possible_cpus())
+			break;
+
+		if (is_little_cpu(cn))
+			cpumask_set_cpu(cpu, slow);
+		else
+			cpumask_set_cpu(cpu, fast);
+
+		cpu++;
+	}
+
+	if (!cpumask_empty(fast) && !cpumask_empty(slow))
+		return;
+
+	/*
+	 * We didn't find both big and little cores so let's call all cores
+	 * fast as this will keep the system running, with all cores being
+	 * treated equal.
+	 */
+	cpumask_setall(fast);
+	cpumask_clear(slow);
+}
+
+#endif /* CONFIG_SCHED_HMP */
+
+
 /*
  * init_cpu_topology is called at boot when only one cpu is running
  * which prevent simultaneous write access to cpu_topology array
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f705a87ac7b5..e05636144c62 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3084,25 +3084,19 @@ done:
 
 #ifdef CONFIG_SCHED_HMP
 /* Heterogenous multiprocessor (HMP) optimizations
- * We need to know which cpus that are fast and slow. Ideally, this
- * information would be provided by the platform in some way. For now it is
- * set in the kernel config. */
+ * We need to know which cpus that are fast and slow. */
 static struct cpumask hmp_fast_cpu_mask;
 static struct cpumask hmp_slow_cpu_mask;
 
-/* Setup fast and slow cpumasks.
- * This should be setup based on device tree somehow. */
+extern void __init arch_get_fast_and_slow_cpus(struct cpumask *fast,
+					       struct cpumask *slow);
+
+/* Setup fast and slow cpumasks. */
 static int __init hmp_cpu_mask_setup(void)
 {
 	char buf[64];
 
-	cpumask_clear(&hmp_fast_cpu_mask);
-	cpumask_clear(&hmp_slow_cpu_mask);
-
-	if (cpulist_parse(CONFIG_HMP_FAST_CPU_MASK, &hmp_fast_cpu_mask))
-		WARN(1, "Failed to parse HMP fast cpu mask!\n");
-	if (cpulist_parse(CONFIG_HMP_SLOW_CPU_MASK, &hmp_slow_cpu_mask))
-		WARN(1, "Failed to parse HMP slow cpu mask!\n");
+	arch_get_fast_and_slow_cpus(&hmp_fast_cpu_mask, &hmp_slow_cpu_mask);
 
 	printk(KERN_DEBUG "Initializing HMP scheduler:\n");
 	cpulist_scnprintf(buf, 64, &hmp_fast_cpu_mask);