[PATCH 3/8] cpufreq: cpufreq-cpu0: add dt node parsing on cooling need

[Eduardo Valentin <eduardo.valentin@ti.com>]

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 boolean
property 'needs-cooling'.

In case this boolean is present, the driver will
load a cpufreq cooling device in the system. The cpufreq-cpu0
driver is not capable of determining how the system should
be using the cooling device. This can be described using device
tree, to determine what needs to be done with the loaded
cpufreq cooling device, in case the system temperature is detected
to be high, with help of temperature sensors (check
Documentation/devicetree/bindings/thermal/thermal.txt).

Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
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
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
---
 .../devicetree/bindings/cpufreq/cpufreq-cpu0.txt   |  3 ++
 .../devicetree/bindings/thermal/thermal.txt        | 34 ++++++++++++++++++++++
 drivers/cpufreq/cpufreq-cpu0.c                     |  8 +++++
 3 files changed, 45 insertions(+)

diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
index 051f764..e8ff916 100644
--- a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
+++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
@@ -15,6 +15,8 @@ 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.
+- needs-cooling: The generic cpu cooling (freq clipping) is loaded by the
+generic cpufreq-cpu0 driver in case the device tree node has this boolean.
 
 Examples:
 
@@ -33,6 +35,7 @@ cpus {
 			198000  850000
 		>;
 		clock-latency = <61036>; /* two CLK32 periods */
+		needs-cooling;
 	};
 
 	cpu@1 {
diff --git a/Documentation/devicetree/bindings/thermal/thermal.txt b/Documentation/devicetree/bindings/thermal/thermal.txt
index 03751bb..ac0c7b9 100644
--- a/Documentation/devicetree/bindings/thermal/thermal.txt
+++ b/Documentation/devicetree/bindings/thermal/thermal.txt
@@ -97,3 +97,37 @@ thermal_zone {
                     };
             };
 };
+
+***************
+cpufreq-cooling
+***************
+
+The generic cpu cooling (freq clipping) can be loaded by the
+generic cpufreq-cpu0 driver in case the device tree node informs
+this need.
+
+In order to load the cpufreq cooling device, it is possible to
+inform that the cpu needs cooling by adding the boolean flag
+'needs-cooling' at the cpu0 phandle.
+
+Example:
+	cpus {
+		cpu@0 {
+			operating-points = <
+				/* kHz    uV */
+				800000  1313000
+				1008000 1375000
+			>;
+			needs-cooling; /* make sure we have cpufreq-cooling */
+		};
+	...
+	};
+
+The above will cause the cpufreq-cpu0 driver to understand that
+the cpu will need passive cooling and while probing that node it will
+also load the cpufreq cpu cooling device in that system.
+
+However, be advised that this flag will not describe what needs to
+be done or how the cpufreq cooling device will be used. In order to
+accomplish this, one needs to write a phandle for a thermal zone, as
+described in the section 'thermal_zone'.
diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
index ad1fde2..4a8747a 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 +272,9 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
 		goto out_free_table;
 	}
 
+	if (of_property_read_bool(np, "needs-cooling"))
+		cdev = cpufreq_cooling_register(cpu_present_mask);
+
 	of_node_put(np);
 	of_node_put(parent);
 	return 0;
@@ -283,6 +290,7 @@ 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