cpufreq: Add a generic cpufreq-cpu0 driver

It adds a generic cpufreq driver for CPU0 frequency management based on
clk, regulator, OPP and device tree support.  It can support both
uniprocessor (UP) and those symmetric multiprocessor (SMP) systems which
share clock and voltage across all CPUs.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: AnilKumar Ch <anilkumar@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt

+Generic CPU0 cpufreq driver
+
+It is a generic cpufreq driver for CPU0 frequency management.  It
+supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
+systems which share clock and voltage across all CPUs.
+
+Both required and optional properties listed below must be defined
+under node /cpus/cpu@0.
+
+Required properties:
+- operating-points: Refer to Documentation/devicetree/bindings/power/opp.txt
+  for details
+
+Optional properties:
+- clock-latency: Specify the possible maximum transition latency for clock,
+  in unit of nanoseconds.
+- voltage-tolerance: Specify the CPU voltage tolerance in percentage.
+
+Examples:
+
+cpus {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	cpu@0 {
+		compatible = "arm,cortex-a9";
+		reg = <0>;
+		next-level-cache = <&L2>;
+		operating-points = <
+			/* kHz    uV */
+			792000  1100000
+			396000  950000
+			198000  850000
+		>;
+		transition-latency = <61036>; /* two CLK32 periods */
+	};
+
+	cpu@1 {
+		compatible = "arm,cortex-a9";
+		reg = <1>;
+		next-level-cache = <&L2>;
+	};
+
+	cpu@2 {
+		compatible = "arm,cortex-a9";
+		reg = <2>;
+		next-level-cache = <&L2>;
+	};
+
+	cpu@3 {
+		compatible = "arm,cortex-a9";
+		reg = <3>;
+		next-level-cache = <&L2>;
+	};
+};

drivers/cpufreq/Kconfig

@@ -179,6 +179,17 @@ config CPU_FREQ_GOV_CONSERVATIVE
 
 	  If in doubt, say N.
 
+config GENERIC_CPUFREQ_CPU0
+	bool "Generic CPU0 cpufreq driver"
+	depends on HAVE_CLK && REGULATOR && PM_OPP && OF
+	select CPU_FREQ_TABLE
+	help
+	  This adds a generic cpufreq driver for CPU0 frequency management.
+	  It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
+	  systems which share clock and voltage across all CPUs.
+
+	  If in doubt, say N.
+
 menu "x86 CPU frequency scaling drivers"
 depends on X86
 source "drivers/cpufreq/Kconfig.x86"

drivers/cpufreq/Makefile

@@ -13,6 +13,8 @@ obj-$(CONFIG_CPU_FREQ_GOV_CONSERVATIVE)	+= cpufreq_conservative.o
 # CPUfreq cross-arch helpers
 obj-$(CONFIG_CPU_FREQ_TABLE)		+= freq_table.o
 
+obj-$(CONFIG_GENERIC_CPUFREQ_CPU0)	+= cpufreq-cpu0.o
+
 ##################################################################################
 # x86 drivers.
 # Link order matters. K8 is preferred to ACPI because of firmware bugs in early

drivers/cpufreq/cpufreq-cpu0.c

+/*
+ * Copyright (C) 2012 Freescale Semiconductor, Inc.
+ *
+ * The OPP code in function cpu0_set_target() is reused from
+ * drivers/cpufreq/omap-cpufreq.c
+ *
+ * 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.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/opp.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+static unsigned int transition_latency;
+static unsigned int voltage_tolerance; /* in percentage */
+
+static struct device *cpu_dev;
+static struct clk *cpu_clk;
+static struct regulator *cpu_reg;
+static struct cpufreq_frequency_table *freq_table;
+
+static int cpu0_verify_speed(struct cpufreq_policy *policy)
+{
+	return cpufreq_frequency_table_verify(policy, freq_table);
+}
+
+static unsigned int cpu0_get_speed(unsigned int cpu)
+{
+	return clk_get_rate(cpu_clk) / 1000;
+}
+
+static int cpu0_set_target(struct cpufreq_policy *policy,
+			   unsigned int target_freq, unsigned int relation)
+{
+	struct cpufreq_freqs freqs;
+	struct opp *opp;
+	unsigned long freq_Hz, volt = 0, volt_old = 0, tol = 0;
+	unsigned int index, cpu;
+	int ret;
+
+	ret = cpufreq_frequency_table_target(policy, freq_table, target_freq,
+					     relation, &index);
+	if (ret) {
+		pr_err("failed to match target freqency %d: %d\n",
+		       target_freq, ret);
+		return ret;
+	}
+
+	freq_Hz = clk_round_rate(cpu_clk, freq_table[index].frequency * 1000);
+	if (freq_Hz < 0)
+		freq_Hz = freq_table[index].frequency * 1000;
+	freqs.new = freq_Hz / 1000;
+	freqs.old = clk_get_rate(cpu_clk) / 1000;
+
+	if (freqs.old == freqs.new)
+		return 0;
+
+	for_each_online_cpu(cpu) {
+		freqs.cpu = cpu;
+		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+	}
+
+	if (cpu_reg) {
+		opp = opp_find_freq_ceil(cpu_dev, &freq_Hz);
+		if (IS_ERR(opp)) {
+			pr_err("failed to find OPP for %ld\n", freq_Hz);
+			return PTR_ERR(opp);
+		}
+		volt = opp_get_voltage(opp);
+		tol = volt * voltage_tolerance / 100;
+		volt_old = regulator_get_voltage(cpu_reg);
+	}
+
+	pr_debug("%u MHz, %ld mV --> %u MHz, %ld mV\n",
+		 freqs.old / 1000, volt_old ? volt_old / 1000 : -1,
+		 freqs.new / 1000, volt ? volt / 1000 : -1);
+
+	/* scaling up?  scale voltage before frequency */
+	if (cpu_reg && freqs.new > freqs.old) {
+		ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
+		if (ret) {
+			pr_err("failed to scale voltage up: %d\n", ret);
+			freqs.new = freqs.old;
+			return ret;
+		}
+	}
+
+	ret = clk_set_rate(cpu_clk, freqs.new * 1000);
+	if (ret) {
+		pr_err("failed to set clock rate: %d\n", ret);
+		if (cpu_reg)
+			regulator_set_voltage_tol(cpu_reg, volt_old, tol);
+		return ret;
+	}
+
+	/* scaling down?  scale voltage after frequency */
+	if (cpu_reg && freqs.new < freqs.old) {
+		ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
+		if (ret) {
+			pr_err("failed to scale voltage down: %d\n", ret);
+			clk_set_rate(cpu_clk, freqs.old * 1000);
+			freqs.new = freqs.old;
+			return ret;
+		}
+	}
+
+	for_each_online_cpu(cpu) {
+		freqs.cpu = cpu;
+		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+	}
+
+	return 0;
+}
+
+static int cpu0_cpufreq_init(struct cpufreq_policy *policy)
+{
+	int ret;
+
+	if (policy->cpu != 0)
+		return -EINVAL;
+
+	ret = cpufreq_frequency_table_cpuinfo(policy, freq_table);
+	if (ret) {
+		pr_err("invalid frequency table: %d\n", ret);
+		return ret;
+	}
+
+	policy->cpuinfo.transition_latency = transition_latency;
+	policy->cur = clk_get_rate(cpu_clk) / 1000;
+
+	/*
+	 * The driver only supports the SMP configuartion where all processors
+	 * share the clock and voltage and clock.  Use cpufreq affected_cpus
+	 * interface to have all CPUs scaled together.
+	 */
+	policy->shared_type = CPUFREQ_SHARED_TYPE_ANY;
+	cpumask_setall(policy->cpus);
+
+	cpufreq_frequency_table_get_attr(freq_table, policy->cpu);
+
+	return 0;
+}
+
+static int cpu0_cpufreq_exit(struct cpufreq_policy *policy)
+{
+	cpufreq_frequency_table_put_attr(policy->cpu);
+
+	return 0;
+}
+
+static struct freq_attr *cpu0_cpufreq_attr[] = {
+	&cpufreq_freq_attr_scaling_available_freqs,
+	NULL,
+};
+
+static struct cpufreq_driver cpu0_cpufreq_driver = {
+	.flags = CPUFREQ_STICKY,
+	.verify = cpu0_verify_speed,
+	.target = cpu0_set_target,
+	.get = cpu0_get_speed,
+	.init = cpu0_cpufreq_init,
+	.exit = cpu0_cpufreq_exit,
+	.name = "generic_cpu0",
+	.attr = cpu0_cpufreq_attr,
+};
+
+static int __devinit cpu0_cpufreq_driver_init(void)
+{
+	struct device_node *np;
+	int ret;
+
+	np = of_find_node_by_path("/cpus/cpu@0");
+	if (!np) {
+		pr_err("failed to find cpu0 node\n");
+		return -ENOENT;
+	}
+
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev) {
+		pr_err("failed to get cpu0 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;
+	}
+
+	cpu_reg = regulator_get(cpu_dev, "cpu0");
+	if (IS_ERR(cpu_reg)) {
+		pr_warn("failed to get cpu0 regulator\n");
+		cpu_reg = NULL;
+	}
+
+	ret = of_init_opp_table(cpu_dev);
+	if (ret) {
+		pr_err("failed to init OPP table: %d\n", ret);
+		goto out_put_node;
+	}
+
+	ret = opp_init_cpufreq_table(cpu_dev, &freq_table);
+	if (ret) {
+		pr_err("failed to init cpufreq table: %d\n", ret);
+		goto out_put_node;
+	}
+
+	of_property_read_u32(np, "voltage-tolerance", &voltage_tolerance);
+
+	if (of_property_read_u32(np, "clock-latency", &transition_latency))
+		transition_latency = CPUFREQ_ETERNAL;
+
+	if (cpu_reg) {
+		struct opp *opp;
+		unsigned long min_uV, max_uV;
+		int i;
+
+		/*
+		 * OPP is maintained in order of increasing frequency, and
+		 * freq_table initialised from OPP is therefore sorted in the
+		 * same order.
+		 */
+		for (i = 0; freq_table[i].frequency != CPUFREQ_TABLE_END; i++)
+			;
+		opp = opp_find_freq_exact(cpu_dev,
+				freq_table[0].frequency * 1000, true);
+		min_uV = opp_get_voltage(opp);
+		opp = opp_find_freq_exact(cpu_dev,
+				freq_table[i-1].frequency * 1000, true);
+		max_uV = opp_get_voltage(opp);
+		ret = regulator_set_voltage_time(cpu_reg, min_uV, max_uV);
+		if (ret > 0)
+			transition_latency += ret * 1000;
+	}
+
+	ret = cpufreq_register_driver(&cpu0_cpufreq_driver);
+	if (ret) {
+		pr_err("failed register driver: %d\n", ret);
+		goto out_free_table;
+	}
+
+	of_node_put(np);
+	return 0;
+
+out_free_table:
+	opp_free_cpufreq_table(cpu_dev, &freq_table);
+out_put_node:
+	of_node_put(np);
+	return ret;
+}
+late_initcall(cpu0_cpufreq_driver_init);
+
+MODULE_AUTHOR("Shawn Guo <shawn.guo@linaro.org>");
+MODULE_DESCRIPTION("Generic CPU0 cpufreq driver");
+MODULE_LICENSE("GPL");