cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue

big LITTLE is ARM's new Architecture focussing power/performance needs of modern
world. More information about big LITTLE can be found here:

http://www.arm.com/products/processors/technologies/biglittleprocessing.php
http://lwn.net/Articles/481055/

In order to keep cpufreq support for all big LITTLE platforms simple/generic,
this patch tries to add a generic cpufreq driver layer for all big LITTLE
platforms.

The driver is divided into two parts:
- Core driver: Generic and shared across all big LITTLE SoC's
- Glue drivers: Per platform drivers providing ops to the core driver

This patch adds in a generic glue driver which would extract information from
Device Tree.

Future SoC's can either reuse the DT glue or write their own depending on the
need.

Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 92 insertions, 0 deletions

diff --git a/drivers/cpufreq/arm_big_little_dt.c b/drivers/cpufreq/arm_big_little_dt.c
new file mode 100644
index 0000000..452ff46
--- /dev/null
+++ b/drivers/cpufreq/arm_big_little_dt.c
@@ -0,0 +1,92 @@
+/*
+ * Generic big.LITTLE CPUFreq Interface driver
+ *
+ * It provides necessary ops to arm_big_little cpufreq driver and gets
+ * Frequency information from Device Tree. Freq table in DT must be in KHz.
+ *
+ * Copyright (C) 2013 Linaro.
+ * Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * 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 "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpufreq.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/opp.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include "arm_big_little.h"
+
+static int dt_init_opp_table(struct device *cpu_dev)
+{
+	struct device_node *np = NULL;
+	int count = 0, ret;
+
+	for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+		if (count++ != cpu_dev->id)
+			continue;
+		if (!of_get_property(np, "operating-points", NULL))
+			return -ENODATA;
+
+		cpu_dev->of_node = np;
+
+		ret = of_init_opp_table(cpu_dev);
+		if (ret)
+			return ret;
+
+		return 0;
+	}
+
+	return -ENODEV;
+}
+
+static int dt_get_transition_latency(struct device *cpu_dev)
+{
+	struct device_node *np = NULL;
+	u32 transition_latency = CPUFREQ_ETERNAL;
+	int count = 0;
+
+	for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+		if (count++ != cpu_dev->id)
+			continue;
+
+		of_property_read_u32(np, "clock-latency", &transition_latency);
+		return 0;
+	}
+
+	return -ENODEV;
+}
+
+static struct cpufreq_arm_bL_ops dt_bL_ops = {
+	.name	= "dt-bl",
+	.get_transition_latency = dt_get_transition_latency,
+	.init_opp_table = dt_init_opp_table,
+};
+
+static int generic_bL_init(void)
+{
+	return bL_cpufreq_register(&dt_bL_ops);
+}
+module_init(generic_bL_init);
+
+static void generic_bL_exit(void)
+{
+	return bL_cpufreq_unregister(&dt_bL_ops);
+}
+module_exit(generic_bL_exit);
+
+MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
+MODULE_DESCRIPTION("Generic ARM big LITTLE cpufreq driver via DT");
+MODULE_LICENSE("GPL");