1 files changed, 183 insertions, 4 deletions

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 7758f7ff131b..d0e5fe5fbf22 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -19,14 +19,36 @@
 #include <linux/nodemask.h>
 #include <linux/of.h>
 #include <linux/sched.h>
+#include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/sched_energy.h>
 
 #include <asm/cputype.h>
 #include <asm/topology.h>
 
+/*
+ * cpu power table
+ * This per cpu data structure describes the relative capacity of each core.
+ * On a heteregenous system, cores don't have the same computation capacity
+ * and we reflect that difference in the cpu_power field so the scheduler can
+ * take this difference into account during load balance. A per cpu structure
+ * is preferred because each CPU updates its own cpu_power field during the
+ * load balance except for idle cores. One idle core is selected to run the
+ * rebalance_domains for all idle cores and the cpu_power can be updated
+ * during this sequence.
+ */
 static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
 
+unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
+{
+	return per_cpu(cpu_scale, cpu);
+}
+
+static void set_power_scale(unsigned int cpu, unsigned long power)
+{
+	per_cpu(cpu_scale, cpu) = power;
+}
+
 unsigned long scale_cpu_capacity(struct sched_domain *sd, int cpu)
 {
 #ifdef CONFIG_CPU_FREQ
@@ -181,6 +203,46 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
 	return 0;
 }
 
+struct cpu_efficiency {
+	const char *compatible;
+	unsigned long efficiency;
+};
+
+/*
+ * Table of relative efficiency of each processors
+ * The efficiency value must fit in 20bit and the final
+ * cpu_scale value must be in the range
+ *   0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
+ * in order to return at most 1 when DIV_ROUND_CLOSEST
+ * is used to compute the capacity of a CPU.
+ * Processors that are not defined in the table,
+ * use the default SCHED_CAPACITY_SCALE value for cpu_scale.
+ */
+static const struct cpu_efficiency table_efficiency[] = {
+	{ NULL, },
+};
+
+static unsigned long *__cpu_capacity;
+#define cpu_capacity(cpu)	__cpu_capacity[cpu]
+
+static unsigned long middle_capacity = 1;
+
+static DEFINE_PER_CPU(unsigned long, cpu_efficiency) = SCHED_CAPACITY_SCALE;
+
+unsigned long arch_get_cpu_efficiency(int cpu)
+{
+	return per_cpu(cpu_efficiency, cpu);
+}
+EXPORT_SYMBOL(arch_get_cpu_efficiency);
+
+/*
+ * Iterate all CPUs' descriptor in DT and compute the efficiency
+ * (as per table_efficiency). Also calculate a middle efficiency
+ * as close as possible to  (max{eff_i} - min{eff_i}) / 2
+ * This is later used to scale the cpu_power field such that an
+ * 'average' CPU is of middle power. Also see the comments near
+ * table_efficiency[] and update_cpu_power().
+ */
 static int __init parse_dt_topology(void)
 {
 	struct device_node *cn, *map;
@@ -220,6 +282,107 @@ out:
 	return ret;
 }
 
+static void __init parse_dt_cpu_power(void)
+{
+	const struct cpu_efficiency *cpu_eff;
+	struct device_node *cn;
+	unsigned long min_capacity = ULONG_MAX;
+	unsigned long max_capacity = 0;
+	unsigned long capacity = 0;
+	int cpu;
+
+	__cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
+				 GFP_NOWAIT);
+
+	for_each_possible_cpu(cpu) {
+		const u32 *rate;
+		int len;
+		u32 efficiency;
+
+		/* Too early to use cpu->of_node */
+		cn = of_get_cpu_node(cpu, NULL);
+		if (!cn) {
+			pr_err("Missing device node for CPU %d\n", cpu);
+			continue;
+		}
+
+		/*
+		 * The CPU efficiency value passed from the device tree
+		 * overrides the value defined in the table_efficiency[]
+		 */
+		if (of_property_read_u32(cn, "efficiency", &efficiency) < 0) {
+
+			for (cpu_eff = table_efficiency;
+					cpu_eff->compatible; cpu_eff++)
+
+				if (of_device_is_compatible(cn,
+						cpu_eff->compatible))
+					break;
+
+			if (cpu_eff->compatible == NULL) {
+				pr_warn("%s: Unknown CPU type\n",
+						cn->full_name);
+				continue;
+			}
+
+			efficiency = cpu_eff->efficiency;
+		}
+
+		per_cpu(cpu_efficiency, cpu) = efficiency;
+
+		rate = of_get_property(cn, "clock-frequency", &len);
+		if (!rate || len != 4) {
+			pr_err("%s: Missing clock-frequency property\n",
+				cn->full_name);
+			continue;
+		}
+
+		capacity = ((be32_to_cpup(rate)) >> 20) * efficiency;
+
+		/* Save min capacity of the system */
+		if (capacity < min_capacity)
+			min_capacity = capacity;
+
+		/* Save max capacity of the system */
+		if (capacity > max_capacity)
+			max_capacity = capacity;
+
+		cpu_capacity(cpu) = capacity;
+	}
+
+	/* If min and max capacities are equal we bypass the update of the
+	 * cpu_scale because all CPUs have the same capacity. Otherwise, we
+	 * compute a middle_capacity factor that will ensure that the capacity
+	 * of an 'average' CPU of the system will be as close as possible to
+	 * SCHED_CAPACITY_SCALE, which is the default value, but with the
+	 * constraint explained near table_efficiency[].
+	 */
+	if (min_capacity == max_capacity)
+		return;
+	else if (4 * max_capacity < (3 * (max_capacity + min_capacity)))
+		middle_capacity = (min_capacity + max_capacity)
+				>> (SCHED_CAPACITY_SHIFT+1);
+	else
+		middle_capacity = ((max_capacity / 3)
+				>> (SCHED_CAPACITY_SHIFT-1)) + 1;
+}
+
+/*
+ * Look for a customed capacity of a CPU in the cpu_topo_data table during the
+ * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
+ * function returns directly for SMP system.
+ */
+static void update_cpu_power(unsigned int cpu)
+{
+	if (!cpu_capacity(cpu))
+		return;
+
+	set_power_scale(cpu, cpu_capacity(cpu) / middle_capacity);
+
+	pr_info("CPU%u: update cpu_power %lu\n",
+		cpu, arch_scale_freq_power(NULL, cpu));
+}
+
 /*
  * cpu topology table
  */
@@ -281,14 +444,14 @@ static void update_cpu_capacity(unsigned int cpu)
 {
 	unsigned long capacity = SCHED_CAPACITY_SCALE;
 
-	if (cpu_core_energy(cpu)) {
+	if (sched_energy_aware && cpu_core_energy(cpu)) {
 		int max_cap_idx = cpu_core_energy(cpu)->nr_cap_states - 1;
 		capacity = cpu_core_energy(cpu)->cap_states[max_cap_idx].cap;
 	}
 
 	set_capacity_scale(cpu, capacity);
 
-	pr_info("CPU%d: update cpu_capacity %lu\n",
+	pr_debug("CPU%d: update cpu_capacity %lu\n",
 		cpu, arch_scale_cpu_capacity(NULL, cpu));
 }
 
@@ -353,6 +516,7 @@ void store_cpu_topology(unsigned int cpuid)
 
 topology_populated:
 	update_siblings_masks(cpuid);
+	update_cpu_power(cpuid);
 	update_cpu_capacity(cpuid);
 }
 
@@ -374,18 +538,33 @@ static void __init reset_cpu_topology(void)
 	}
 }
 
+static void __init reset_cpu_power(void)
+{
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu)
+		set_power_scale(cpu, SCHED_CAPACITY_SCALE);
+}
+
 void __init init_cpu_topology(void)
 {
+	int cpu;
+
 	reset_cpu_topology();
 
 	/*
 	 * Discard anything that was parsed if we hit an error so we
 	 * don't use partial information.
 	 */
-	if (of_have_populated_dt() && parse_dt_topology())
+	if (of_have_populated_dt() && parse_dt_topology()) {
 		reset_cpu_topology();
-	else
+	} else {
 		set_sched_topology(arm64_topology);
+		for_each_possible_cpu(cpu)
+			update_siblings_masks(cpu);
+	}
 
+	reset_cpu_power();
+	parse_dt_cpu_power();
 	init_sched_energy_costs();
 }