[RFC PATCH 01/14] cpufreq: cpufreq-cpu0: add dt node parsing for 'cooling-zones'

[Eduardo Valentin]

This patch changes the cpufreq-cpu0 driver to consider if
a cpu needs cooling (with cpufreq). In case the cooling is needed,
it can be flagged at the cpu0 device tree node, with the list
of zones property 'cooling-zones'.

In case this list of zones is 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@xxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: Grant Likely <grant.likely@xxxxxxxxxx>
Cc: Rob Herring <rob.herring@xxxxxxxxxxx>
Cc: cpufreq@xxxxxxxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: devicetree-discuss@xxxxxxxxxxxxxxxx
Signed-off-by: Eduardo Valentin <eduardo.valentin@xxxxxx>
---
 Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt |  4 ++++
 drivers/cpufreq/cpufreq-cpu0.c                             | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
index 051f764..add50f7 100644
--- a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
+++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
@@ -15,6 +15,9 @@ 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-zones: A list of thermal zones phandles. The generic cpu
+  cooling (freq clipping) is loaded by the generic cpufreq-cpu0 driver
+  in case the device tree node has this list.
 
 Examples:
 
@@ -33,6 +36,7 @@ cpus {
 			198000  850000
 		>;
 		clock-latency = <61036>; /* two CLK32 periods */
+		cooling-zones = <&cpu_thermal>;
 	};
 
 	cpu@1 {
diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
index ad1fde2..ede6487 100644
--- a/drivers/cpufreq/cpufreq-cpu0.c
+++ b/drivers/cpufreq/cpufreq-cpu0.c
@@ -20,6 +20,9 @@
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
+#include <linux/thermal.h>
+#include <linux/cpu_cooling.h>
+#include <linux/cpumask.h>
 
 static unsigned int transition_latency;
 static unsigned int voltage_tolerance; /* in percentage */
@@ -28,6 +31,7 @@ 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 int cpu0_verify_speed(struct cpufreq_policy *policy)
 {
@@ -268,6 +272,13 @@ 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-zones", NULL))
+		cdev = cpufreq_cooling_register(cpu_present_mask);
+
 	of_node_put(np);
 	of_node_put(parent);
 	return 0;
@@ -283,6 +294,7 @@ out_put_parent:
 
 static int cpu0_cpufreq_remove(struct platform_device *pdev)
 {
+	cpufreq_cooling_unregister(cdev);
 	cpufreq_unregister_driver(&cpu0_cpufreq_driver);
 	opp_free_cpufreq_table(cpu_dev, &freq_table);
 
-- 
1.8.2.1.342.gfa7285d

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