debug: debug_stream: log per-core utilization from idle thread load

Keep the per-thread stack and cpu LOG_DBG print and add a separate
LOG_INF that fires only for the Zephyr idle thread. The info-level
print reports per-core CPU utilization calculated as the inverse of
the idle thread load percentage.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

Author: kv2019i

src/debug/debug_stream/debug_stream_thread_info.c

@@ -7,6 +7,7 @@
 #include <rtos/alloc.h>
 #include <ipc/topology.h>
 #include <stdio.h>
+#include <string.h>
 #include <soc.h>
 #include <adsp_debug_window.h>
 
@@ -225,6 +226,10 @@ static void thread_info_cb(const struct k_thread *cthread, void *user_data)
 		tinfo->name, tinfo->stack_usage * 100U / 255,
 		tinfo->cpu_usage * 100U / 255);
 
+	if (name && strncmp(name, "idle", 4) == 0)
+		LOG_INF("core %u utilization %u%%", ud->core,
+			100U - tinfo->cpu_usage * 100U / 255);
+
 	ud->thread_count++;
 }