sched: Hook SCHED_USAGE from existing tracing hook

On older architectures, we don't have the
architecture-independent/scheduler-internal hooks (which require
USE_SWITCH) but there is a hook shared by the tracing layer we can use.

This is sort of a layering violation (stat tracking is a core feature,
tracing is supposed to be optional), but simple and lightweight.  And
eventually it will go away as these architectures migrate.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>

kernel/Kconfig

@@ -379,7 +379,7 @@ config INSTRUMENT_THREAD_SWITCHING
 
 config SCHED_THREAD_USAGE
 	bool "Collect thread runtime usage"
-	depends on USE_SWITCH
+	select INSTRUMENT_THREAD_SWITCHING if !USE_SWITCH
 	help
 	  Alternate implementation of thread runtime cycle usage
 

kernel/sched.c

@@ -1737,6 +1737,11 @@ int z_sched_wait(struct k_spinlock *lock, k_spinlock_key_t key,
 
 #ifdef CONFIG_SCHED_THREAD_USAGE
 
+/* Need one of these for this to work */
+#if !defined(CONFIG_USE_SWITCH) && !defined(CONFIG_INSTRUMENT_THREAD_SWITCHING)
+#error "No data backend configured for CONFIG_SCHED_THREAD_USAGE"
+#endif
+
 static struct k_spinlock usage_lock;
 
 static uint32_t usage_now(void)

kernel/thread.c

@@ -1006,6 +1006,10 @@ static inline k_ticks_t z_vrfy_k_thread_timeout_expires_ticks(
 #ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
 void z_thread_mark_switched_in(void)
 {
+#if defined(CONFIG_SCHED_THREAD_USAGE) && !defined(CONFIG_USE_SWITCH)
+	z_sched_usage_start(_current);
+#endif
+
 #ifdef CONFIG_TRACING
 	SYS_PORT_TRACING_FUNC(k_thread, switched_in);
 #endif
@@ -1025,6 +1029,10 @@ void z_thread_mark_switched_in(void)
 
 void z_thread_mark_switched_out(void)
 {
+#if defined(CONFIG_SCHED_THREAD_USAGE) && !defined(CONFIG_USE_SWITCH)
+	z_sched_usage_stop();
+#endif
+
 #ifdef CONFIG_THREAD_RUNTIME_STATS
 #ifdef CONFIG_THREAD_RUNTIME_STATS_USE_TIMING_FUNCTIONS
 	timing_t now;