cpufreq: arm_big_little: add vexpress SPC interface driver

The TC2(i.e. CA15_A7) Versatile Express has external Cortex M3 based
power controller which is responsible for CPU DVFS and SPC provides
the interface for the same.

This patch adds a tiny interface driver to check if OPPs are
initialised by SPC platform code and register the arm_big_little
cpufreq driver.

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

drivers/cpufreq/Kconfig.arm

@@ -224,3 +224,11 @@ config ARM_TEGRA_CPUFREQ
 	default y
 	help
 	  This adds the CPUFreq driver support for TEGRA SOCs.
+
+config ARM_VEXPRESS_SPC_CPUFREQ
+        tristate "Versatile Express SPC based CPUfreq driver"
+        select ARM_BIG_LITTLE_CPUFREQ
+        depends on ARCH_VEXPRESS_SPC
+        help
+          This add the CPUfreq driver support for Versatile Express
+	  big.LITTLE platforms using SPC for power management.

drivers/cpufreq/Makefile

@@ -74,6 +74,7 @@ obj-$(CONFIG_ARM_SA1100_CPUFREQ)	+= sa1100-cpufreq.o
 obj-$(CONFIG_ARM_SA1110_CPUFREQ)	+= sa1110-cpufreq.o
 obj-$(CONFIG_ARM_SPEAR_CPUFREQ)		+= spear-cpufreq.o
 obj-$(CONFIG_ARM_TEGRA_CPUFREQ)		+= tegra-cpufreq.o
+obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ)	+= vexpress-spc-cpufreq.o
 
 ##################################################################################
 # PowerPC platform drivers

drivers/cpufreq/vexpress-spc-cpufreq.c

@@ -0,0 +1,70 @@
+/*
+ * Versatile Express SPC CPUFreq Interface driver
+ *
+ * It provides necessary ops to arm_big_little cpufreq driver.
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ * Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
+ *
+ * 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/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_opp.h>
+#include <linux/types.h>
+
+#include "arm_big_little.h"
+
+static int ve_spc_init_opp_table(struct device *cpu_dev)
+{
+	/*
+	 * platform specific SPC code must initialise the opp table
+	 * so just check if the OPP count is non-zero
+	 */
+	return dev_pm_opp_get_opp_count(cpu_dev) <= 0;
+}
+
+static int ve_spc_get_transition_latency(struct device *cpu_dev)
+{
+	return 1000000; /* 1 ms */
+}
+
+static struct cpufreq_arm_bL_ops ve_spc_cpufreq_ops = {
+	.name	= "vexpress-spc",
+	.get_transition_latency = ve_spc_get_transition_latency,
+	.init_opp_table = ve_spc_init_opp_table,
+};
+
+static int ve_spc_cpufreq_probe(struct platform_device *pdev)
+{
+	return bL_cpufreq_register(&ve_spc_cpufreq_ops);
+}
+
+static int ve_spc_cpufreq_remove(struct platform_device *pdev)
+{
+	bL_cpufreq_unregister(&ve_spc_cpufreq_ops);
+	return 0;
+}
+
+static struct platform_driver ve_spc_cpufreq_platdrv = {
+	.driver = {
+		.name	= "vexpress-spc-cpufreq",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= ve_spc_cpufreq_probe,
+	.remove		= ve_spc_cpufreq_remove,
+};
+module_platform_driver(ve_spc_cpufreq_platdrv);
+
+MODULE_LICENSE("GPL");