arch: xtensa: Add hifi_owner for lazy switching

Adds a customized _cpu_arch structure for Xtensa so that it contains
a pointer to the thread that 'owns' the hifi register set for use
with lazy save/restore.

Signed-off-by: Peter Mitsis <[email protected]>

Author: peter-mitsis

include/zephyr/arch/structs.h

@@ -31,6 +31,8 @@
 #include <zephyr/arch/arm/structs.h>
 #elif defined(CONFIG_X86) && !defined(CONFIG_X86_64)
 #include <zephyr/arch/x86/ia32/structs.h>
+#elif defined(CONFIG_XTENSA)
+#include <zephyr/arch/xtensa/structs.h>
 #else
 
 /* Default definitions when no architecture specific definitions exist. */

include/zephyr/arch/xtensa/structs.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_XTENSA_STRUCTS_H_
+#define ZEPHYR_INCLUDE_XTENSA_STRUCTS_H_
+
+/* Per CPU architecture specifics */
+struct _cpu_arch {
+#if defined(CONFIG_XTENSA_LAZY_HIFI_SHARING)
+	atomic_ptr_val_t hifi_owner; /* Owner of HiFi */
+#if CONFIG_MP_MAX_NUM_CPUS > 1
+	atomic_ptr_val_t save_hifi;  /* Save HiFi on IPI if match hifi_owner */
+#endif
+#elif defined(__cplusplus)
+	/* Ensure this struct does not have a size of 0 which is not allowed in C++. */
+	uint8_t dummy;
+#endif
+};
+
+#endif /* ZEPHYR_INCLUDE_XTENSA_STRUCTS_H_ */