init: introduce soc and board hooks

Introduce soc and board hooks to replace arch specific code
and replace usages of SYS_INIT for platform initialization.

include/zephyr/platform/hooks.h introduces the hooks to be implemented
by boards and SoCs.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

arch/arc/core/prep_c.c

@@ -23,6 +23,7 @@
 #include <zephyr/arch/arc/cluster.h>
 #include <zephyr/kernel_structs.h>
 #include <kernel_internal.h>
+#include <zephyr/platform/hooks.h>
 
 /* XXX - keep for future use in full-featured cache APIs */
 #if 0
@@ -121,6 +122,10 @@ extern FUNC_NORETURN void z_cstart(void);
 
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
+
 #ifdef CONFIG_ISA_ARCV3
 	arc_cluster_scm_enable();
 #endif

arch/arm/core/cortex_a_r/prep_c.c

@@ -21,6 +21,7 @@
 #include <zephyr/linker/linker-defs.h>
 #include <zephyr/sys/barrier.h>
 #include <zephyr/arch/arm/cortex_a_r/lib_helpers.h>
+#include <zephyr/platform/hooks.h>
 
 #if defined(CONFIG_ARMV7_R) || defined(CONFIG_ARMV7_A)
 #include <cortex_a_r/stack.h>
@@ -147,6 +148,9 @@ extern FUNC_NORETURN void z_cstart(void);
  */
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
 	/* Initialize tpidruro with our struct _cpu instance address */
 	write_tpidruro((uintptr_t)&_kernel.cpus[0]);
 

arch/arm/core/cortex_m/prep_c.c

@@ -20,6 +20,7 @@
 #include <kernel_internal.h>
 #include <zephyr/linker/linker-defs.h>
 #include <zephyr/sys/barrier.h>
+#include <zephyr/platform/hooks.h>
 
 #if defined(__GNUC__)
 /*
@@ -181,6 +182,10 @@ extern FUNC_NORETURN void z_cstart(void);
  */
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
+
 	relocate_vector_table();
 #if defined(CONFIG_CPU_HAS_FPU)
 	z_arm_floating_point_init();

arch/arm64/core/prep_c.c

@@ -16,6 +16,7 @@
 
 #include <kernel_internal.h>
 #include <zephyr/linker/linker-defs.h>
+#include <zephyr/platform/hooks.h>
 
 extern void z_arm64_mm_init(bool is_primary_core);
 
@@ -30,6 +31,10 @@ __weak void z_arm64_mm_init(bool is_primary_core) { }
  */
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
+
 	/* Initialize tpidrro_el0 with our struct _cpu instance address */
 	write_tpidrro_el0((uintptr_t)&_kernel.cpus[0]);
 

arch/mips/core/prep_c.c

@@ -11,6 +11,7 @@
 
 #include <kernel_internal.h>
 #include <zephyr/irq.h>
+#include <zephyr/platform/hooks.h>
 
 static void interrupt_init(void)
 {
@@ -44,6 +45,9 @@ static void interrupt_init(void)
 
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
 	z_bss_zero();
 
 	interrupt_init();

arch/nios2/core/prep_c.c

@@ -21,6 +21,7 @@
 #include <zephyr/linker/linker-defs.h>
 #include <zephyr/kernel_structs.h>
 #include <kernel_internal.h>
+#include <zephyr/platform/hooks.h>
 
 /**
  * @brief Prepare to and run C code
@@ -30,6 +31,10 @@
 
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
+
 	z_bss_zero();
 	z_data_copy();
 	/* In most XIP scenarios we copy the exception code into RAM, so need

arch/riscv/core/prep_c.c

@@ -19,6 +19,7 @@
 #include <zephyr/toolchain.h>
 #include <zephyr/kernel_structs.h>
 #include <kernel_internal.h>
+#include <zephyr/platform/hooks.h>
 
 #if defined(CONFIG_RISCV_SOC_INTERRUPT_INIT)
 void soc_interrupt_init(void);
@@ -33,6 +34,10 @@ void soc_interrupt_init(void);
 
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
+
 	z_bss_zero();
 	z_data_copy();
 #if defined(CONFIG_RISCV_SOC_INTERRUPT_INIT)

arch/sparc/core/prep_c.c

@@ -10,6 +10,7 @@
  */
 
 #include <kernel_internal.h>
+#include <zephyr/platform/hooks.h>
 
 /**
  * @brief Prepare to and run C code
@@ -19,6 +20,9 @@
 
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
 	z_data_copy();
 	z_cstart();
 	CODE_UNREACHABLE;

arch/x86/core/prep_c.c

@@ -9,6 +9,7 @@
 #include <zephyr/arch/x86/multiboot.h>
 #include <zephyr/arch/x86/efi.h>
 #include <x86_mmu.h>
+#include <zephyr/platform/hooks.h>
 
 extern FUNC_NORETURN void z_cstart(void);
 extern void x86_64_irq_init(void);
@@ -25,6 +26,9 @@ FUNC_NORETURN void z_prep_c(void *arg)
 {
 	x86_boot_arg_t *cpu_arg = arg;
 
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
 	_kernel.cpus[0].nested = 0;
 
 #ifdef CONFIG_MMU

arch/xtensa/core/prep_c.c

@@ -5,6 +5,7 @@
  */
 #include <zephyr/kernel.h>
 #include <kernel_internal.h>
+#include <zephyr/platform/hooks.h>
 
 extern FUNC_NORETURN void z_cstart(void);
 
@@ -20,6 +21,9 @@ extern void soc_num_cpus_init(void);
  */
 void z_prep_c(void)
 {
+#if defined(CONFIG_SOC_PREP_HOOK)
+	soc_prep_hook();
+#endif
 #if CONFIG_SOC_HAS_RUNTIME_NUM_CPUS
 	soc_num_cpus_init();
 #endif

include/zephyr/platform/hooks.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2024 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef ZEPHYR_INCLUDE_PLATFORM_PLATFORM_H_
+#define ZEPHYR_INCLUDE_PLATFORM_PLATFORM_H_
+
+/**
+ * @file
+ * @brief Soc and Board hooks
+ *
+ * This header file contains function prototypes for the interfaces between
+ * zephyr architecture and initialization code and the SoC and board specific logic
+ * that resides under boards/ and soc/
+ *
+ * @note These are all standard soc and board interfaces that are exported from
+ * soc and board specific logic to OS internal logic.  These should never be accessed
+ * directly from application code but may be freely used within the OS.
+ */
+
+
+/**
+ * @brief SoC  hook executed at the beginning of the reset vector.
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific initialization.
+ */
+void soc_reset_hook(void);
+
+/**
+ * @brief SoC hook executed after the reset vector.
+ *
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific initialization.
+ */
+void soc_prep_hook(void);
+
+/*
+ * @brief SoC hook executed before the kernel and devices are initialized.
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific initialization.
+ */
+void soc_early_init_hook(void);
+
+/*
+ * @brief SoC hook executed after the kernel and devices are initialized.
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific initialization.
+ */
+void soc_late_init_hook(void);
+
+/*
+ * @brief Board hook executed before the kernel starts.
+ *
+ * This is called before the kernel has started. This hook
+ * is implemented by the board and can be used to perform any board-specific
+ * initialization.
+ */
+void board_early_init_hook(void);
+
+/*
+ * @brief Board hook executed after the kernel starts.
+
+ * This is called after the kernel has started, but before the main function is
+ * called. This hook is implemented by the board and can be used to perform
+ * any board-specific initialization.
+ */
+void board_late_init_hook(void);
+
+#endif

kernel/Kconfig

@@ -1027,3 +1027,4 @@ endmenu
 
 rsource "Kconfig.device"
 rsource "Kconfig.vm"
+rsource "Kconfig.init"

kernel/Kconfig.init

@@ -0,0 +1,45 @@
+# Kernel init hook options
+
+# Copyright (c) 2024 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+
+menu "SoC and Board Hooks"
+
+config SOC_RESET_HOOK
+	bool "Run early SoC reset hook"
+	help
+	  Run an early SoC reset hook.
+
+	  A custom hook soc_reset_hook() is executed at the beginning of the
+	  startup code (__start). soc_reset_hook() must be implemented by the SoC.
+
+config SOC_PREP_HOOK
+	bool "Run early SoC preparation hook"
+	help
+	  Run an early SoC preparation hook.
+
+	  A custom hook soc_prep_hook() is executed at the beginning of the
+	  c prep code (prep_c). soc_prep_hook() must be implemented by the SoC.
+
+config SOC_EARLY_INIT_HOOK
+	bool "Run early SoC hook"
+	help
+	  Run an early SoC initialization hook.
+
+config SOC_LATE_INIT_HOOK
+	bool "Run late SoC hook"
+	help
+	  Run a late SoC initialization hook.
+
+config BOARD_EARLY_INIT_HOOK
+	bool "Run early board hook"
+	help
+	  Run an early board initialization hook.
+
+config BOARD_LATE_INIT_HOOK
+	bool "Run late board hook"
+	help
+	  Run a late board initialization hook.
+
+endmenu

kernel/init.c

@@ -25,6 +25,7 @@
 #include <zephyr/device.h>
 #include <zephyr/init.h>
 #include <zephyr/linker/linker-defs.h>
+#include <zephyr/platform/hooks.h>
 #include <ksched.h>
 #include <kthread.h>
 #include <zephyr/sys/dlist.h>
@@ -516,6 +517,13 @@ static void bg_thread_main(void *unused1, void *unused2, void *unused3)
 	z_sys_post_kernel = true;
 
 	z_sys_init_run_level(INIT_LEVEL_POST_KERNEL);
+#if CONFIG_SOC_LATE_INIT_HOOK
+	soc_late_init_hook();
+#endif
+#if CONFIG_BOARD_LATE_INIT_HOOK
+	board_late_init_hook();
+#endif
+
 #if defined(CONFIG_STACK_POINTER_RANDOM) && (CONFIG_STACK_POINTER_RANDOM != 0)
 	z_stack_adjust_initialized = 1;
 #endif /* CONFIG_STACK_POINTER_RANDOM */
@@ -757,6 +765,12 @@ FUNC_NORETURN void z_cstart(void)
 	/* do any necessary initialization of static devices */
 	z_device_state_init();
 
+#if CONFIG_SOC_EARLY_INIT_HOOK
+	soc_early_init_hook();
+#endif
+#if CONFIG_BOARD_EARLY_INIT_HOOK
+	board_early_init_hook();
+#endif
 	/* perform basic hardware initialization */
 	z_sys_init_run_level(INIT_LEVEL_PRE_KERNEL_1);
 #if defined(CONFIG_SMP)