arm64: topology: Add support for topology DT bindings

Add support for parsing the explicit topology bindings to discover the
topology of the system.

Since it is not currently clear how to map multi-level clusters for the
scheduler all leaf clusters are presented to the scheduler at the same
level. This should be enough to provide good support for current systems.

Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 130 insertions, 0 deletions

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index c88970b1b86..83d6919d4e0 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -79,6 +79,121 @@ static unsigned long *__cpu_capacity;
 #define cpu_capacity(cpu)	__cpu_capacity[cpu]
 
 static unsigned long middle_capacity = 1;
+static int cluster_id;
+
+static int __init get_cpu_for_node(struct device_node *node)
+{
+	struct device_node *cpu_node;
+	int cpu;
+
+	cpu_node = of_parse_phandle(node, "cpu", 0);
+	if (!cpu_node) {
+		pr_crit("%s: Unable to parse CPU phandle\n", node->full_name);
+		return -1;
+	}
+
+	for_each_possible_cpu(cpu) {
+		if (of_get_cpu_node(cpu, NULL) == cpu_node)
+			return cpu;
+	}
+
+	pr_crit("Unable to find CPU node for %s\n", cpu_node->full_name);
+	return -1;
+}
+
+static void __init parse_core(struct device_node *core, int core_id)
+{
+	char name[10];
+	bool leaf = true;
+	int i, cpu;
+	struct device_node *t;
+
+	i = 0;
+	do {
+		snprintf(name, sizeof(name), "thread%d", i);
+		t = of_get_child_by_name(core, name);
+		if (t) {
+			leaf = false;
+			cpu = get_cpu_for_node(t);
+			if (cpu) {
+				pr_info("CPU%d: socket %d core %d thread %d\n",
+					cpu, cluster_id, core_id, i);
+				cpu_topology[cpu].socket_id = cluster_id;
+				cpu_topology[cpu].core_id = core_id;
+				cpu_topology[cpu].thread_id = i;
+			} else {
+				pr_err("%s: Can't get CPU for thread\n",
+				       t->full_name);
+			}
+		}
+		i++;
+	} while (t);
+
+	cpu = get_cpu_for_node(core);
+	if (cpu >= 0) {
+		if (!leaf) {
+			pr_err("%s: Core has both threads and CPU\n",
+			       core->full_name);
+			return;
+		}
+
+		pr_info("CPU%d: socket %d core %d\n",
+			cpu, cluster_id, core_id);
+		cpu_topology[cpu].socket_id = cluster_id;
+		cpu_topology[cpu].core_id = core_id;
+	} else if (leaf) {
+		pr_err("%s: Can't get CPU for leaf core\n", core->full_name);
+	}
+}
+
+static void __init parse_cluster(struct device_node *cluster)
+{
+	char name[10];
+	bool leaf = true;
+	bool has_cores = false;
+	struct device_node *c;
+	int core_id = 0;
+	int i;
+
+	/*
+	 * First check for child clusters; we currently ignore any
+	 * information about the nesting of clusters and present the
+	 * scheduler with a flat list of them.
+	 */
+	i = 0;
+	do {
+		snprintf(name, sizeof(name), "cluster%d", i);
+		c = of_get_child_by_name(cluster, name);
+		if (c) {
+			parse_cluster(c);
+			leaf = false;
+		}
+		i++;
+	} while (c);
+
+	/* Now check for cores */
+	i = 0;
+	do {
+		snprintf(name, sizeof(name), "core%d", i);
+		c = of_get_child_by_name(cluster, name);
+		if (c) {
+			has_cores = true;
+
+			if (leaf)
+				parse_core(c, core_id++);
+			else
+				pr_err("%s: Non-leaf cluster with core %s\n",
+				       cluster->full_name, name);
+		}
+		i++;
+	} while (c);
+
+	if (leaf && !has_cores)
+		pr_warn("%s: empty cluster\n", cluster->full_name);
+
+	if (leaf)
+		cluster_id++;
+}
 
 /*
  * Iterate all CPUs' descriptor in DT and compute the efficiency
@@ -100,6 +215,21 @@ static void __init parse_dt_topology(void)
 	alloc_size = nr_cpu_ids * sizeof(*__cpu_capacity);
 	__cpu_capacity = kzalloc(alloc_size, GFP_NOWAIT);
 
+	cn = of_find_node_by_path("/cpus");
+	if (!cn) {
+		pr_err("No CPU information found in DT\n");
+		return;
+	}
+
+	/*
+	 * If topology is provided as a cpu-map it is essentially a
+	 * root cluster.
+	 */
+	cn = of_find_node_by_name(cn, "cpu-map");
+	if (!cn)
+		return;
+	parse_cluster(cn);
+
 	for_each_possible_cpu(cpu) {
 		const u32 *rate;
 		int len;