cpufreq: exynos: Use device tree to determine if cpufreq cooling should be registered

With thermal subsystem rework it is necessary to tune current cpufreq code
to use cpu frequency change as a potential cooling device.

Now the cpu cooling device is registered only when proper nodes and properties
are available in device tree. Lack of them, however, will not prevent
cpufreq for normal operation.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/cpufreq/exynos-cpufreq.c

@@ -18,10 +18,13 @@
 #include <linux/cpufreq.h>
 #include <linux/platform_device.h>
 #include <linux/of.h>
+#include <linux/cpu_cooling.h>
+#include <linux/cpu.h>
 
 #include "exynos-cpufreq.h"
 
 static struct exynos_dvfs_info *exynos_info;
+static struct thermal_cooling_device *cdev;
 static struct regulator *arm_regulator;
 static unsigned int locking_frequency;
 
@@ -156,6 +159,7 @@ static struct cpufreq_driver exynos_driver = {
 
 static int exynos_cpufreq_probe(struct platform_device *pdev)
 {
+	struct device_node *cpus, *np;
 	int ret = -EINVAL;
 
 	exynos_info = kzalloc(sizeof(*exynos_info), GFP_KERNEL);
@@ -198,9 +202,36 @@ static int exynos_cpufreq_probe(struct platform_device *pdev)
 	/* Done here as we want to capture boot frequency */
 	locking_frequency = clk_get_rate(exynos_info->cpu_clk) / 1000;
 
-	if (!cpufreq_register_driver(&exynos_driver))
-		return 0;
+	ret = cpufreq_register_driver(&exynos_driver);
+	if (ret)
+		goto err_cpufreq_reg;
 
+	cpus = of_find_node_by_path("/cpus");
+	if (!cpus) {
+		pr_err("failed to find cpus node\n");
+		return 0;
+	}
+
+	np = of_get_next_child(cpus, NULL);
+	if (!np) {
+		pr_err("failed to find cpus child node\n");
+		of_node_put(cpus);
+		return 0;
+	}
+
+	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);
+	of_node_put(cpus);
+
+	return 0;
+
+err_cpufreq_reg:
 	dev_err(&pdev->dev, "failed to register cpufreq driver\n");
 	regulator_put(arm_regulator);
 err_vdd_arm: