sched: Support for extracting EAS energy costs from DT

This patch implements support for extracting energy cost data from DT.
The data should conform to the DT bindings for energy cost data needed
by EAS (energy aware scheduling).

Signed-off-by: Robin Randhawa <robin.randhawa@arm.com>

3 files changed, 161 insertions, 1 deletions

diff --git a/include/linux/sched_energy.h b/include/linux/sched_energy.h
new file mode 100644
index 000000000000..a3f1627ac609
--- /dev/null
+++ b/include/linux/sched_energy.h
@@ -0,0 +1,36 @@
+#ifndef _LINUX_SCHED_ENERGY_H
+#define _LINUX_SCHED_ENERGY_H
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+/*
+ * There doesn't seem to be an NR_CPUS style max number of sched domain
+ * levels so here's an arbitrary constant one for the moment.
+ *
+ * The levels alluded to here correspond to entries in struct
+ * sched_domain_topology_level that are meant to be populated by arch
+ * specific code (topology.c).
+ */
+#define NR_SD_LEVELS 8
+
+#define SD_LEVEL0   0
+#define SD_LEVEL1   1
+#define SD_LEVEL2   2
+#define SD_LEVEL3   3
+#define SD_LEVEL4   4
+#define SD_LEVEL5   5
+#define SD_LEVEL6   6
+#define SD_LEVEL7   7
+
+/*
+ * Convenience macro for iterating through said sd levels.
+ */
+#define for_each_possible_sd_level(level)		    \
+	for (level = 0; level < NR_SD_LEVELS; level++)
+
+extern struct sched_group_energy *sge_array[NR_CPUS][NR_SD_LEVELS];
+
+void init_sched_energy_costs(void);
+
+#endif
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 67687973ce80..a541b5ce1dcc 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -12,7 +12,7 @@ CFLAGS_core.o := $(PROFILING) -fno-omit-frame-pointer
 endif
 
 obj-y += core.o loadavg.o clock.o cputime.o
-obj-y += idle_task.o fair.o rt.o deadline.o stop_task.o
+obj-y += idle_task.o fair.o rt.o deadline.o stop_task.o energy.o
 obj-y += wait.o completion.o idle.o
 obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o
 obj-$(CONFIG_SCHED_AUTOGROUP) += auto_group.o
diff --git a/kernel/sched/energy.c b/kernel/sched/energy.c
new file mode 100644
index 000000000000..b0656b7a93e3
--- /dev/null
+++ b/kernel/sched/energy.c
@@ -0,0 +1,124 @@
+/*
+ * Obtain energy cost data from DT and populate relevant scheduler data
+ * structures.
+ *
+ * Copyright (C) 2015 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#define pr_fmt(fmt) "sched-energy: " fmt
+
+#define DEBUG
+
+#include <linux/gfp.h>
+#include <linux/of.h>
+#include <linux/printk.h>
+#include <linux/sched.h>
+#include <linux/sched_energy.h>
+#include <linux/stddef.h>
+
+struct sched_group_energy *sge_array[NR_CPUS][NR_SD_LEVELS];
+
+static void free_resources(void)
+{
+	int cpu, sd_level;
+	struct sched_group_energy *sge;
+
+	for_each_possible_cpu(cpu) {
+		for_each_possible_sd_level(sd_level) {
+			sge = sge_array[cpu][sd_level];
+			if (sge) {
+				kfree(sge->cap_states);
+				kfree(sge->idle_states);
+				kfree(sge);
+			}
+		}
+	}
+}
+
+void init_sched_energy_costs(void)
+{
+	struct device_node *cn, *cp;
+	struct capacity_state *cap_states;
+	struct idle_state *idle_states;
+	struct sched_group_energy *sge;
+	const struct property *prop;
+	int sd_level, i, nstates, cpu;
+	const __be32 *val;
+
+	for_each_possible_cpu(cpu) {
+		cn = of_get_cpu_node(cpu, NULL);
+		if (!cn) {
+			pr_warn("CPU device node missing for CPU %d\n", cpu);
+			return;
+		}
+
+		if (!of_find_property(cn, "sched-energy-costs", NULL)) {
+			pr_warn("CPU device node has no sched-energy-costs\n");
+			return;
+		}
+
+		for_each_possible_sd_level(sd_level) {
+			cp = of_parse_phandle(cn, "sched-energy-costs", sd_level);
+			if (!cp)
+				break;
+
+			prop = of_find_property(cp, "busy-cost-data", NULL);
+			if (!prop || !prop->value) {
+				pr_warn("No busy-cost data, skipping sched_energy init\n");
+				goto out;
+			}
+
+			sge = kcalloc(1, sizeof(struct sched_group_energy),
+				      GFP_NOWAIT);
+
+			nstates = (prop->length / sizeof(u32)) / 2;
+			cap_states = kcalloc(nstates,
+					     sizeof(struct capacity_state),
+					     GFP_NOWAIT);
+
+			for (i = 0, val = prop->value; i < nstates; i++) {
+				cap_states[i].cap = be32_to_cpup(val++);
+				cap_states[i].power = be32_to_cpup(val++);
+			}
+
+			sge->nr_cap_states = nstates;
+			sge->cap_states = cap_states;
+
+			prop = of_find_property(cp, "idle-cost-data", NULL);
+			if (!prop || !prop->value) {
+				pr_warn("No idle-cost data, skipping sched_energy init\n");
+				goto out;
+			}
+
+			nstates = (prop->length / sizeof(u32));
+			idle_states = kcalloc(nstates,
+					      sizeof(struct idle_state),
+					      GFP_NOWAIT);
+
+			for (i = 0, val = prop->value; i < nstates; i++)
+				idle_states[i].power = be32_to_cpup(val++);
+
+			sge->nr_idle_states = nstates;
+			sge->idle_states = idle_states;
+
+			sge_array[cpu][sd_level] = sge;
+		}
+	}
+
+	pr_info("Sched-energy-costs installed from DT\n");
+	return;
+
+out:
+	free_resources();
+}