cpufreq / highbank: add support for highbank cpufreq

Highbank processors depend on the external ECME to perform voltage
management based on a requested frequency. Communication between the
A9 cores and the ECME happens over the pl320 IPC channel.

Signed-off-by: Mark Langsdorf <mark.langsdorf@calxeda.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/arm/boot/dts/highbank.dts

@@ -37,6 +37,16 @@ cpu@900 {
 			next-level-cache = <&L2>;
 			clocks = <&a9pll>;
 			clock-names = "cpu";
+			operating-points = <
+				/* kHz    ignored */
+				 1300000  1000000
+				 1200000  1000000
+				 1100000  1000000
+				  800000  1000000
+				  400000  1000000
+				  200000  1000000
+			>;
+			clock-latency = <100000>;
 		};
 
 		cpu@901 {

arch/arm/mach-highbank/Kconfig

@@ -1,5 +1,7 @@
 config ARCH_HIGHBANK
 	bool "Calxeda ECX-1000/2000 (Highbank/Midway)" if ARCH_MULTI_V7
+	select ARCH_HAS_CPUFREQ
+	select ARCH_HAS_OPP
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select ARM_AMBA
 	select ARM_GIC

drivers/cpufreq/Kconfig.arm

@@ -83,3 +83,18 @@ config ARM_SPEAR_CPUFREQ
 	default y
 	help
 	  This adds the CPUFreq driver support for SPEAr SOCs.
+
+config ARM_HIGHBANK_CPUFREQ
+	tristate "Calxeda Highbank-based"
+	depends on ARCH_HIGHBANK
+	select CPU_FREQ_TABLE
+	select GENERIC_CPUFREQ_CPU0
+	select PM_OPP
+	select REGULATOR
+
+	default m
+	help
+	  This adds the CPUFreq driver for Calxeda Highbank SoC
+	  based boards.
+
+	  If in doubt, say N.

drivers/cpufreq/Makefile

@@ -53,6 +53,7 @@ obj-$(CONFIG_ARM_EXYNOS4X12_CPUFREQ)	+= exynos4x12-cpufreq.o
 obj-$(CONFIG_ARM_EXYNOS5250_CPUFREQ)	+= exynos5250-cpufreq.o
 obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ)	+= omap-cpufreq.o
 obj-$(CONFIG_ARM_SPEAR_CPUFREQ)		+= spear-cpufreq.o
+obj-$(CONFIG_ARM_HIGHBANK_CPUFREQ)	+= highbank-cpufreq.o
 
 ##################################################################################
 # PowerPC platform drivers

drivers/cpufreq/cpufreq-cpu0.c

@@ -182,7 +182,11 @@ static int cpu0_cpufreq_driver_init(void)
 	struct device_node *np;
 	int ret;
 
-	np = of_find_node_by_path("/cpus/cpu@0");
+	for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+		if (of_get_property(np, "operating-points", NULL))
+			break;
+	}
+
 	if (!np) {
 		pr_err("failed to find cpu0 node\n");
 		return -ENOENT;

drivers/cpufreq/highbank-cpufreq.c

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2012 Calxeda, Inc.
+ *
+ * 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 driver provides the clk notifier callbacks that are used when
+ * the cpufreq-cpu0 driver changes to frequency to alert the highbank
+ * EnergyCore Management Engine (ECME) about the need to change
+ * voltage. The ECME interfaces with the actual voltage regulators.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/mailbox.h>
+
+#define HB_CPUFREQ_CHANGE_NOTE	0x80000001
+#define HB_CPUFREQ_IPC_LEN	7
+#define HB_CPUFREQ_VOLT_RETRIES	15
+
+static int hb_voltage_change(unsigned int freq)
+{
+	int i;
+	u32 msg[HB_CPUFREQ_IPC_LEN];
+
+	msg[0] = HB_CPUFREQ_CHANGE_NOTE;
+	msg[1] = freq / 1000000;
+	for (i = 2; i < HB_CPUFREQ_IPC_LEN; i++)
+		msg[i] = 0;
+
+	return pl320_ipc_transmit(msg);
+}
+
+static int hb_cpufreq_clk_notify(struct notifier_block *nb,
+				unsigned long action, void *hclk)
+{
+	struct clk_notifier_data *clk_data = hclk;
+	int i = 0;
+
+	if (action == PRE_RATE_CHANGE) {
+		if (clk_data->new_rate > clk_data->old_rate)
+			while (hb_voltage_change(clk_data->new_rate))
+				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
+					return NOTIFY_BAD;
+	} else if (action == POST_RATE_CHANGE) {
+		if (clk_data->new_rate < clk_data->old_rate)
+			while (hb_voltage_change(clk_data->new_rate))
+				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
+					return NOTIFY_BAD;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block hb_cpufreq_clk_nb = {
+	.notifier_call = hb_cpufreq_clk_notify,
+};
+
+static int hb_cpufreq_driver_init(void)
+{
+	struct device *cpu_dev;
+	struct clk *cpu_clk;
+	struct device_node *np;
+	int ret;
+
+	if (!of_machine_is_compatible("calxeda,highbank"))
+		return -ENODEV;
+
+	for_each_child_of_node(of_find_node_by_path("/cpus"), np)
+		if (of_get_property(np, "operating-points", NULL))
+			break;
+
+	if (!np) {
+		pr_err("failed to find highbank cpufreq node\n");
+		return -ENOENT;
+	}
+
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev) {
+		pr_err("failed to get highbank cpufreq device\n");
+		ret = -ENODEV;
+		goto out_put_node;
+	}
+
+	cpu_dev->of_node = np;
+
+	cpu_clk = clk_get(cpu_dev, NULL);
+	if (IS_ERR(cpu_clk)) {
+		ret = PTR_ERR(cpu_clk);
+		pr_err("failed to get cpu0 clock: %d\n", ret);
+		goto out_put_node;
+	}
+
+	ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
+	if (ret) {
+		pr_err("failed to register clk notifier: %d\n", ret);
+		goto out_put_node;
+	}
+
+out_put_node:
+	of_node_put(np);
+	return ret;
+}
+module_init(hb_cpufreq_driver_init);
+
+MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
+MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
+MODULE_LICENSE("GPL");