[RFC/PATCH 10/12] cpufreq: Add a cpufreq-krait based on cpufreq-cpu0

[Stephen Boyd]

Krait processors have individual clocks for each CPU that can
scale independently from one another. cpufreq-cpu0 is fairly
close to this, but assumes that there is only one clock for all
CPUs. Add a driver to support the Krait configuration.

TODO: Merge into cpufreq-cpu0? Or make generic?

Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
---
 drivers/cpufreq/Kconfig         |  13 +++
 drivers/cpufreq/Makefile        |   1 +
 drivers/cpufreq/cpufreq-krait.c | 190 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 204 insertions(+)
 create mode 100644 drivers/cpufreq/cpufreq-krait.c

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index ffe350f86bca..e9826c85a777 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -196,6 +196,19 @@ config GENERIC_CPUFREQ_CPU0
 
 	  If in doubt, say N.
 
+config GENERIC_CPUFREQ_KRAIT
+	tristate "Krait cpufreq driver"
+	depends on HAVE_CLK && OF
+	# if CPU_THERMAL is on and THERMAL=m, CPU0 cannot be =y:
+	depends on !CPU_THERMAL || THERMAL
+	select PM_OPP
+	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"
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 738c8b7b17dc..f5c9f68dcc0f 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_CPU_FREQ_GOV_CONSERVATIVE)	+= cpufreq_conservative.o
 obj-$(CONFIG_CPU_FREQ_GOV_COMMON)		+= cpufreq_governor.o
 
 obj-$(CONFIG_GENERIC_CPUFREQ_CPU0)	+= cpufreq-cpu0.o
+obj-$(CONFIG_CPUFREQ_KRAIT)		+= cpufreq-krait.o
 
 ##################################################################################
 # x86 drivers.
diff --git a/drivers/cpufreq/cpufreq-krait.c b/drivers/cpufreq/cpufreq-krait.c
new file mode 100644
index 000000000000..7b38b9c948e5
--- /dev/null
+++ b/drivers/cpufreq/cpufreq-krait.c
@@ -0,0 +1,190 @@
+/*
+ * Copyright (C) 2012 Freescale Semiconductor, Inc.
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * The OPP code in function krait_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.
+ */
+
+#include <linux/clk.h>
+#include <linux/cpu.h>
+#include <linux/cpu_cooling.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pm_opp.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/thermal.h>
+
+static unsigned int transition_latency;
+
+static struct device *cpu_dev;
+static DEFINE_PER_CPU(struct clk *, krait_cpu_clks);
+static struct cpufreq_frequency_table *freq_table;
+static struct thermal_cooling_device *cdev;
+
+static int krait_set_target(struct cpufreq_policy *policy, unsigned int index)
+{
+	unsigned long volt = 0, volt_old = 0;
+	unsigned int old_freq, new_freq;
+	long freq_Hz, freq_exact;
+	int ret;
+	struct clk *cpu_clk;
+
+	cpu_clk = per_cpu(krait_cpu_clks, policy->cpu);
+
+	freq_Hz = clk_round_rate(cpu_clk, freq_table[index].frequency * 1000);
+	if (freq_Hz <= 0)
+		freq_Hz = freq_table[index].frequency * 1000;
+
+	freq_exact = freq_Hz;
+	new_freq = freq_Hz / 1000;
+	old_freq = clk_get_rate(cpu_clk) / 1000;
+
+	pr_debug("%u MHz, %ld mV --> %u MHz, %ld mV\n",
+		 old_freq / 1000, volt_old ? volt_old / 1000 : -1,
+		 new_freq / 1000, volt ? volt / 1000 : -1);
+
+	ret = clk_set_rate(cpu_clk, freq_exact);
+	if (ret)
+		pr_err("failed to set clock rate: %d\n", ret);
+
+	return ret;
+}
+
+static int krait_cpufreq_init(struct cpufreq_policy *policy)
+{
+	int ret;
+
+	policy->clk = per_cpu(krait_cpu_clks, policy->cpu);
+
+	ret = cpufreq_table_validate_and_show(policy, freq_table);
+	if (ret) {
+		pr_err("%s: invalid frequency table: %d\n", __func__, ret);
+		return ret;
+	}
+
+	policy->cpuinfo.transition_latency = transition_latency;
+
+	return 0;
+}
+
+static struct cpufreq_driver krait_cpufreq_driver = {
+	.flags = CPUFREQ_STICKY,
+	.verify = cpufreq_generic_frequency_table_verify,
+	.target_index = krait_set_target,
+	.get = cpufreq_generic_get,
+	.init = krait_cpufreq_init,
+	.name = "generic_krait",
+	.attr = cpufreq_generic_attr,
+};
+
+static int krait_cpufreq_probe(struct platform_device *pdev)
+{
+	struct device_node *np;
+	int ret;
+	unsigned int cpu;
+	struct device *dev;
+	struct clk *clk;
+
+	cpu_dev = get_cpu_device(0);
+	if (!cpu_dev) {
+		pr_err("failed to get krait device\n");
+		return -ENODEV;
+	}
+
+	np = of_node_get(cpu_dev->of_node);
+	if (!np) {
+		pr_err("failed to find krait node\n");
+		return -ENOENT;
+	}
+
+	for_each_possible_cpu(cpu) {
+		dev = get_cpu_device(cpu);
+		if (!dev) {
+			pr_err("failed to get krait device\n");
+			ret = -ENOENT;
+			goto out_put_node;
+		}
+		per_cpu(krait_cpu_clks, cpu) = clk = devm_clk_get(dev, NULL);
+		if (IS_ERR(clk)) {
+			ret = PTR_ERR(clk);
+			goto out_put_node;
+		}
+	}
+
+	ret = of_init_opp_table(cpu_dev);
+	if (ret) {
+		pr_err("failed to init OPP table: %d\n", ret);
+		goto out_put_node;
+	}
+
+	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
+	if (ret) {
+		pr_err("failed to init cpufreq table: %d\n", ret);
+		goto out_put_node;
+	}
+
+	if (of_property_read_u32(np, "clock-latency", &transition_latency))
+		transition_latency = CPUFREQ_ETERNAL;
+
+	ret = cpufreq_register_driver(&krait_cpufreq_driver);
+	if (ret) {
+		pr_err("failed register driver: %d\n", ret);
+		goto out_free_table;
+	}
+	of_node_put(np);
+
+	/*
+	 * For now, just loading the cooling device;
+	 * thermal DT code takes care of matching them.
+	 */
+	for_each_possible_cpu(cpu) {
+		dev = get_cpu_device(cpu);
+		np = of_node_get(dev->of_node);
+		if (of_find_property(np, "#cooling-cells", NULL)) {
+			cdev = of_cpufreq_cooling_register(np, cpumask_of(cpu));
+			if (IS_ERR(cdev))
+				pr_err("running cpufreq without cooling device: %ld\n",
+				       PTR_ERR(cdev));
+		}
+		of_node_put(np);
+	}
+
+	return 0;
+
+out_free_table:
+	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
+out_put_node:
+	of_node_put(np);
+	return ret;
+}
+
+static int krait_cpufreq_remove(struct platform_device *pdev)
+{
+	cpufreq_cooling_unregister(cdev);
+	cpufreq_unregister_driver(&krait_cpufreq_driver);
+	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
+
+	return 0;
+}
+
+static struct platform_driver krait_cpufreq_platdrv = {
+	.driver = {
+		.name	= "cpufreq-krait",
+		.owner	= THIS_MODULE,
+	},
+	.probe		= krait_cpufreq_probe,
+	.remove		= krait_cpufreq_remove,
+};
+module_platform_driver(krait_cpufreq_platdrv);
+
+MODULE_DESCRIPTION("Krait CPUfreq driver");
+MODULE_LICENSE("GPL v2");
-- 
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