cpufreq: scmi: Fix OPP addition failure with a dummy clock provider

Commit dd461cd918 ("opp: Allow dev_pm_opp_get_opp_table() to return
-EPROBE_DEFER") handles -EPROBE_DEFER for the clock/interconnects within
_allocate_opp_table() which is called from dev_pm_opp_add and it
now propagates the error back to the caller.

SCMI performance domain re-used clock bindings to keep it simple. However
with the above mentioned change, if clock property is present in a device
node, opps fails to get added with below errors until clk_get succeeds.

 cpu0: failed to add opp 450000000Hz
 cpu0: failed to add opps to the device
 ....(errors on cpu1-cpu4)
 cpu5: failed to add opp 450000000Hz
 cpu5: failed to add opps to the device

So, in order to fix the issue, we need to register dummy clock provider.
With the dummy clock provider, clk_get returns NULL(no errors!), then opp
core proceeds to add OPPs for the CPUs.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Fixes: dd461cd918 ("opp: Allow dev_pm_opp_get_opp_table() to return -EPROBE_DEFER")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/scmi-cpufreq.c

@@ -8,6 +8,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/clk-provider.h>
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/cpumask.h>
@@ -228,12 +229,17 @@ static struct cpufreq_driver scmi_cpufreq_driver = {
 static int scmi_cpufreq_probe(struct scmi_device *sdev)
 {
 	int ret;
+	struct device *dev = &sdev->dev;
 
 	handle = sdev->handle;
 
 	if (!handle || !handle->perf_ops)
 		return -ENODEV;
 
+	/* dummy clock provider as needed by OPP if clocks property is used */
+	if (of_find_property(dev->of_node, "#clock-cells", NULL))
+		devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get, NULL);
+
 	ret = cpufreq_register_driver(&scmi_cpufreq_driver);
 	if (ret) {
 		dev_err(&sdev->dev, "%s: registering cpufreq failed, err: %d\n",