thermal: cpu_cooling: check for the readiness of cpufreq layer

In this patch, the cpu_cooling code checks for the usability of cpufreq
layer before proceeding with the CPU cooling device registration. The
main reason is: CPU cooling device is not usable if cpufreq cannot
switch frequencies.

Similar checks are spread in thermal drivers. Thus, the advantage now
is to have the check in a single place: cpu cooling device registration.
For this reason, this patch also updates the existing drivers that
depend on CPU cooling to simply propagate the error code of the cpu
cooling registration call. Therefore, in case cpufreq is not ready, the
thermal drivers will still return -EPROBE_DEFER, in an attempt to try
again when cpufreq layer gets ready.

Cc: devicetree@vger.kernel.org
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/cpu_cooling.c

@@ -443,6 +443,11 @@ __cpufreq_cooling_register(struct device_node *np,
 	int ret = 0, i;
 	struct cpufreq_policy policy;
 
+	if (!cpufreq_frequency_get_table(cpumask_first(clip_cpus))) {
+		pr_debug("%s: CPUFreq table not found\n", __func__);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
 	/* Verify that all the clip cpus have same freq_min, freq_max limit */
 	for_each_cpu(i, clip_cpus) {
 		/* continue if cpufreq policy not found and not return error */