From d666f161564f2d9608be7234399d2483c63e75db Mon Sep 17 00:00:00 2001
From: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>
Date: Wed, 11 Oct 2023 10:39:51 +0200
Subject: [PATCH] Add support for Zephyr's native test environment

Zephyr's native test environment is a setup
which allows building the embedded SW with the Zephyr OS
and HW models as a Linux executable.

When building for this target the Zephyr integration
will set METAL_PROCESSOR_HEADERS_ON_SYSTEM.

We need to provide appropriate headers
for this environment.
The "metal_cpu_yield()" call, which in other
architectures is handled as either a hint for the CPU to yield
to another thread or do nothing, and therefore
busy waiting, needs replacing with a call out to
the Zephyr API which will cause the CPU to waste 1 microsecond,
therefore enabling the other CPU in the system to ready
whatever we are waiting for in the meanwhile.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

(f) Add support for Zephyr's POSIX architecture

(f) Add support for Zephyr's native
---
 libmetal/lib/CMakeLists.txt               |  7 +++++-
 libmetal/lib/atomic.h                     |  4 ++++
 libmetal/lib/cpu.h                        |  4 ++++
 libmetal/lib/system/zephyr/CMakeLists.txt |  3 +++
 libmetal/lib/system/zephyr/cpu.h          | 26 +++++++++++++++++++++++
 5 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 libmetal/lib/system/zephyr/cpu.h

diff --git a/libmetal/lib/CMakeLists.txt b/libmetal/lib/CMakeLists.txt
index e9d5276..c8dd7d2 100644
--- a/libmetal/lib/CMakeLists.txt
+++ b/libmetal/lib/CMakeLists.txt
@@ -41,7 +41,9 @@ collect (PROJECT_LIB_SOURCES softirq.c)
 collect (PROJECT_LIB_SOURCES version.c)
 
 add_subdirectory (compiler)
-add_subdirectory (processor)
+if (NOT DEFINED METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+  add_subdirectory (processor)
+endif()
 add_subdirectory (system)
 
 collector_list (_inc_dirs PROJECT_INC_DIRS)
@@ -72,6 +74,9 @@ if (WITH_ZEPHYR)
   add_dependencies(metal offsets_h)
   zephyr_library_sources(${_sources})
   zephyr_include_directories(${CMAKE_CURRENT_BINARY_DIR}/include)
+  if (DEFINED METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+    zephyr_compile_definitions(METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+  endif()
 else (WITH_ZEPHYR)
   # Build a shared library if so configured.
   if (WITH_SHARED_LIB)
diff --git a/libmetal/lib/atomic.h b/libmetal/lib/atomic.h
index 44d6b9a..e0f387a 100644
--- a/libmetal/lib/atomic.h
+++ b/libmetal/lib/atomic.h
@@ -101,7 +101,11 @@ using std::atomic_signal_fence;
 #elif defined(__GNUC__)
 # include <metal/compiler/gcc/atomic.h>
 #else
+#if defined(METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+# include <metal/system/@PROJECT_SYSTEM@/atomic.h>
+#else
 # include <metal/processor/@PROJECT_PROCESSOR@/atomic.h>
 #endif
+#endif
 
 #endif /* __METAL_ATOMIC__H__ */
diff --git a/libmetal/lib/cpu.h b/libmetal/lib/cpu.h
index 9deade6..2a94cdb 100644
--- a/libmetal/lib/cpu.h
+++ b/libmetal/lib/cpu.h
@@ -12,6 +12,10 @@
 #ifndef __METAL_CPU__H__
 #define __METAL_CPU__H__
 
+#if defined(METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+# include <metal/system/@PROJECT_SYSTEM@/cpu.h>
+#else
 # include <metal/processor/@PROJECT_PROCESSOR@/cpu.h>
+#endif
 
 #endif /* __METAL_CPU__H__ */
diff --git a/libmetal/lib/system/zephyr/CMakeLists.txt b/libmetal/lib/system/zephyr/CMakeLists.txt
index 43cd1b6..6605b9a 100644
--- a/libmetal/lib/system/zephyr/CMakeLists.txt
+++ b/libmetal/lib/system/zephyr/CMakeLists.txt
@@ -8,6 +8,9 @@ collect (PROJECT_LIB_HEADERS log.h)
 collect (PROJECT_LIB_HEADERS mutex.h)
 collect (PROJECT_LIB_HEADERS sleep.h)
 collect (PROJECT_LIB_HEADERS sys.h)
+if (DEFINED METAL_PROCESSOR_HEADERS_ON_SYSTEM)
+  collect (PROJECT_LIB_HEADERS cpu.h)
+endif()
 
 collect (PROJECT_LIB_SOURCES alloc.c)
 collect (PROJECT_LIB_SOURCES condition.c)
diff --git a/libmetal/lib/system/zephyr/cpu.h b/libmetal/lib/system/zephyr/cpu.h
new file mode 100644
index 0000000..364557a
--- /dev/null
+++ b/libmetal/lib/system/zephyr/cpu.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/*
+ * @file	cpu.h
+ * @brief	Zephyr native test environment CPU specific primitives
+ */
+
+#ifndef __METAL_ZEPHYR_CPU__H__
+#define __METAL_ZEPHYR_CPU__H__
+
+#include <zephyr/kernel.h>
+
+static inline void metal_cpu_yield(void)
+{
+	/*
+	 * In Zephyr's native test environment let 1 microsecond pass
+	 *  to allow other threads to run
+	 */
+	k_busy_wait(1);
+};
+
+#endif /* __METAL_ZEPHYR_CPU__H__ */