cpufreq: trace frequency limits change

systrace used for tracing for Android systems has carried a patch for
many years in the Android tree that traces when the cpufreq limits
change. With the help of this information, systrace can know when the
policy limits change and can visually display the data. Lets add
upstream support for the same.

Signed-off-by: Ruchi Kandoi <[e-mail]>
Signed-off-by: Joel Fernandes (Google) <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Acked-by: Steven Rostedt (VMware) <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

Documentation/trace/events-power.rst

···
 
   cpu_idle		"state=%lu cpu_id=%lu"
   cpu_frequency		"state=%lu cpu_id=%lu"
+  cpu_frequency_limits	"min=%lu max=%lu cpu_id=%lu"
 
 A suspend event is used to indicate the system going in and out of the
 suspend mode:

drivers/cpufreq/cpufreq.c

···
 
 	policy->min = new_policy->min;
 	policy->max = new_policy->max;
+	trace_cpu_frequency_limits(policy);
 
 	policy->cached_target_freq = UINT_MAX;
 

include/trace/events/power.h

···
 #if !defined(_TRACE_POWER_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_POWER_H
 
+#include <linux/cpufreq.h>
 #include <linux/ktime.h>
 #include <linux/pm_qos.h>
 #include <linux/tracepoint.h>
···
 	TP_PROTO(unsigned int frequency, unsigned int cpu_id),
 
 	TP_ARGS(frequency, cpu_id)
+);
+
+TRACE_EVENT(cpu_frequency_limits,
+
+	TP_PROTO(struct cpufreq_policy *policy),
+
+	TP_ARGS(policy),
+
+	TP_STRUCT__entry(
+		__field(u32, min_freq)
+		__field(u32, max_freq)
+		__field(u32, cpu_id)
+	),
+
+	TP_fast_assign(
+		__entry->min_freq = policy->min;
+		__entry->max_freq = policy->max;
+		__entry->cpu_id = policy->cpu;
+	),
+
+	TP_printk("min=%lu max=%lu cpu_id=%lu",
+		  (unsigned long)__entry->min_freq,
+		  (unsigned long)__entry->max_freq,
+		  (unsigned long)__entry->cpu_id)
 );
 
 TRACE_EVENT(device_pm_callback_start,