lib: system: create a new libmetal API metal_yield

Define metal_yield in sys.h files is more flexible to manage this
in libmetal, metal_yield would be managed at the OS level and
dispatched to metal_cpu_yield, metal_sleep_usec, or others.

Signed-off-by: Yongrong Wang <wangyongrong@xiaomi.com>

lib/system/freertos/sys.h

@@ -18,6 +18,7 @@
 #define __METAL_FREERTOS_SYS__H__
 
 #include <metal/errno.h>
+#include <metal/cpu.h>
 
 #ifdef XLNX_PLATFORM
 #include <metal/system/freertos/xlnx/sys.h>
@@ -33,6 +34,8 @@ extern "C" {
 #define METAL_MAX_DEVICE_REGIONS 1
 #endif
 
+#define metal_yield() metal_cpu_yield()
+
 /** Structure for FreeRTOS libmetal runtime state. */
 struct metal_state {
 

lib/system/freertos/template/sys.h

@@ -16,10 +16,14 @@
 #ifndef __METAL_FREERTOS_TEMPLATE_SYS__H__
 #define __METAL_FREERTOS_TEMPLATE_SYS__H__
 
+#include <metal/cpu.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#define metal_yield() metal_cpu_yield()
+
 #ifdef METAL_INTERNAL
 
 void sys_irq_enable(unsigned int vector);

lib/system/freertos/xlnx/sys.h

@@ -17,6 +17,8 @@
 #ifndef __METAL_FREERTOS_XLNX_SYS__H__
 #define __METAL_FREERTOS_XLNX_SYS__H__
 
+#include <metal/cpu.h>
+
 #include "xscugic.h"
 #include "FreeRTOS.h"
 
@@ -24,6 +26,8 @@
 extern "C" {
 #endif
 
+#define metal_yield() metal_cpu_yield()
+
 #if defined(SDT) && defined(PLATFORM_ZYNQ)
 #define XPAR_SCUGIC_0_DIST_BASEADDR XPAR_SCUGIC_DIST_BASEADDR
 #endif

lib/system/linux/sys.h

@@ -19,6 +19,7 @@
 #include <fcntl.h>
 #include <libgen.h>
 #include <limits.h>
+#include <metal/cpu.h>
 #include <metal/errno.h>
 #include <pthread.h>
 #include <stdio.h>
@@ -46,6 +47,8 @@ extern "C" {
 #define METAL_INVALID_VADDR     NULL
 #define MAX_PAGE_SIZES		32
 
+#define metal_yield() metal_cpu_yield()
+
 struct metal_device;
 
 /** Structure of shared page or hugepage sized data. */

lib/system/nuttx/sys.h

@@ -16,10 +16,14 @@
 #ifndef __METAL_NUTTX_SYS__H__
 #define __METAL_NUTTX_SYS__H__
 
+#include <metal/sleep.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#define metal_yield() metal_sleep_usec(1000)
+
 #define METAL_INIT_DEFAULTS				\
 {							\
 	.log_handler	= (metal_log_handler)syslog,	\

lib/system/zephyr/sys.h

@@ -16,6 +16,7 @@
 #ifndef __METAL_ZEPHYR_SYS__H__
 #define __METAL_ZEPHYR_SYS__H__
 
+#include <metal/cpu.h>
 #include <stdlib.h>
 #include <zephyr/kernel.h>
 
@@ -23,6 +24,8 @@
 extern "C" {
 #endif
 
+#define metal_yield() metal_cpu_yield()
+
 #define METAL_INIT_DEFAULTS				\
 {							\
 	.log_handler	= metal_zephyr_log_handler,	\