cpufreq: cpufreq-cpu0: add dt node parsing for cooling device properties

This patch changes the cpufreq-cpu0 driver to consider if
a cpu needs cooling (with cpufreq). In case the cooling is needed,
the cpu0 device tree node needs to be properly configured
with cooling device properties.

In case these properties are present,, the driver will
load a cpufreq cooling device in the system. The cpufreq-cpu0
driver is not interested in determining how the system should
be using the cooling device. The driver is responsible
only of loading the cooling device.

Describing how the cooling device will be used can be
accomplished by setting up a thermal zone that references
and is composed by the cpufreq cooling device.

Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: cpufreq@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: devicetree-discuss@lists.ozlabs.org
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>

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

@@ -15,6 +15,10 @@ 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.
+- #cooling-cells:
+- cooling-min-level:
+- cooling-max-level:
+     Please refer to Documentation/devicetree/bindings/thermal/thermal.txt.
 
 Examples:
 
@@ -33,6 +37,9 @@ cpus {
 			198000  850000
 		>;
 		clock-latency = <61036>; /* two CLK32 periods */
+		#cooling-cells = <2>;
+		cooling-min-level = <0>;
+		cooling-max-level = <2>;
 	};
 
 	cpu@1 {

drivers/cpufreq/Kconfig

@@ -181,7 +181,7 @@ config CPU_FREQ_GOV_CONSERVATIVE
 
 config GENERIC_CPUFREQ_CPU0
 	tristate "Generic CPU0 cpufreq driver"
-	depends on HAVE_CLK && REGULATOR && PM_OPP && OF
+	depends on HAVE_CLK && REGULATOR && PM_OPP && OF && THERMAL && CPU_THERMAL
 	help
 	  This adds a generic cpufreq driver for CPU0 frequency management.
 	  It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)

drivers/cpufreq/cpufreq-cpu0.c

@@ -13,7 +13,9 @@
 
 #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>
@@ -21,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
+#include <linux/thermal.h>
 
 static unsigned int transition_latency;
 static unsigned int voltage_tolerance; /* in percentage */
@@ -29,6 +32,7 @@ static struct device *cpu_dev;
 static struct clk *cpu_clk;
 static struct regulator *cpu_reg;
 static struct cpufreq_frequency_table *freq_table;
+static struct thermal_cooling_device *cdev;
 
 static unsigned int cpu0_get_speed(unsigned int cpu)
 {
@@ -201,6 +205,17 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
 		goto out_free_table;
 	}
 
+	/*
+	 * For now, just loading the cooling device;
+	 * thermal DT code takes care of matching them.
+	 */
+	if (of_find_property(np, "#cooling-cells", NULL)) {
+		cdev = of_cpufreq_cooling_register(np, cpu_present_mask);
+		if (IS_ERR(cdev))
+			pr_err("running cpufreq without cooling device: %ld\n",
+			       PTR_ERR(cdev));
+	}
+
 	of_node_put(np);
 	return 0;
 
@@ -213,6 +228,7 @@ out_put_node:
 
 static int cpu0_cpufreq_remove(struct platform_device *pdev)
 {
+	cpufreq_cooling_unregister(cdev);
 	cpufreq_unregister_driver(&cpu0_cpufreq_driver);
 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);