[nrf fromtree] arch/arm/cortex_m: support for bridge to the next image S2RAM resume routines

arch/arm/core/cortex_m/reset.S

@@ -35,6 +35,10 @@ GTEXT(z_arm_init_arch_hw_at_boot)
 #if defined(CONFIG_PM_S2RAM)
 GTEXT(arch_pm_s2ram_resume)
 #endif
+#if defined(CONFIG_SOC_EARLY_RESET_HOOK)
+GTEXT(soc_early_reset_hook)
+#endif
+
 
 /*
  * PACBTI Mask for CONTROL register:
@@ -100,18 +104,11 @@ SECTION_SUBSEC_FUNC(TEXT,_reset_section,__start)
 
 #endif /* CONFIG_INIT_ARCH_HW_AT_BOOT */
 
+#if defined(CONFIG_SOC_EARLY_RESET_HOOK)
+    /* Call custom code that executes before any stack is set up or RAM memory is accessed */
+    bl soc_early_reset_hook
+#endif
 #if defined(CONFIG_PM_S2RAM)
-#if DT_NODE_EXISTS(DT_NODELABEL(pm_s2ram_stack)) &&\
-	DT_NODE_HAS_COMPAT(DT_NODELABEL(pm_s2ram_stack), zephyr_memory_region)
-    /* In certain scenarios, the interrupt stack is actually not safe to overwrite.
-     * For example, when MCUboot is used, the bootloader's "z_interrupt_stack" and the
-     * loaded image's "z_interrupt_stacks" are NOT at the same address, and writing to
-     * the former would corrupt unrelated data from the loaded image. To support such
-     * scenarios, if the Device Tree provides a specially named "zephyr,memory-region",
-     * use it as the stack to run arch_pm_s2ram_resume instead of the interrupt stack.
-     */
-    ldr r0, =DT_REG_ADDR(DT_NODELABEL(pm_s2ram_stack)) + DT_REG_SIZE(DT_NODELABEL(pm_s2ram_stack))
-#else
     /*
      * Temporarily set MSP to interrupt stack so that arch_pm_s2ram_resume can
      * use stack for calling pm_s2ram_mark_check_and_clear.
@@ -124,7 +121,6 @@ SECTION_SUBSEC_FUNC(TEXT,_reset_section,__start)
      * a short while, there is no change in behavior in either of the paths.
      */
     ldr r0, =z_interrupt_stacks + CONFIG_ISR_STACK_SIZE + MPU_GUARD_ALIGN_AND_SIZE
-#endif
     msr msp, r0
 
     bl arch_pm_s2ram_resume

include/zephyr/platform/hooks.h

@@ -19,6 +19,19 @@
  * directly from application code but may be freely used within the OS.
  */
 
+#ifdef CONFIG_SOC_EARLY_RESET_HOOK
+/**
+ * @brief SoC hook executed before data RAM initialization, at the beginning
+ * of the reset vector.
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific initialization. Refer to :kconfig:option:`SOC_EARLY_RESET_HOOK`
+ * and relevant architecture zephyr-rtos startup implementation for more details.
+ */
+void soc_early_reset_hook(void);
+#else
+#define soc_early_reset_hook() do { } while (0)
+#endif
 
 /**
  * @brief SoC  hook executed at the beginning of the reset vector.

kernel/Kconfig.init

@@ -6,6 +6,28 @@
 
 menu "SoC and Board Hooks"
 
+config SOC_EARLY_RESET_HOOK
+	bool "Run SoC-specific early reset hook"
+	help
+	  Run a SoC-specific hook early in the reset/startup code (__start).
+	  A custom hook soc_early_reset_hook() will be executed at the beginning
+	  of the architecture-specific startup code, after hardware has been
+	  configured (as required by CONFIG_INIT_ARCH_HW_AT_BOOT) but before
+	  architecture's own resume logic.
+
+	  Returning from this hook is not mandatory: it can be used to implement
+	  special logic to resume execution in some scenarios (for example, when
+	  a bootloader is used).
+
+	  The stack pointer register should be considered as not initialized upon
+	  call to this hook. In particular, this means that the hook is NOT allowed
+	  to "push" any data using this stack pointer value. However, the hook may
+	  use an implementation-specific area as stack if desired; in such case,
+	  the original value of the stack pointer needs not to be "restored" before
+	  returning control to the hook's caller.
+
+	  Additional constraints may be imposed on the hook by the architecture.
+
 config SOC_RESET_HOOK
 	bool "Run early SoC reset hook"
 	help

subsys/pm/Kconfig

@@ -41,11 +41,6 @@ config PM_S2RAM
 	  When enabled on Cortex-M, and a 'zephyr,memory-region' compatible node with nodelabel
 	  'pm_s2ram' is defined in DT, _cpu_context symbol (located in arch/arm/core/cortex_m/pm_s2ram.c)
 	  is placed in linker section given by 'zephyr,memory-region' property of aforementioned node.
-	  Additionally on Cortex-M, if a 'zephyr,memory-region' compatible node with nodelabel
-	  'pm_s2ram_stack' is defined in DT, this region will be used as a temporary program stack
-	  for the S2RAM resume logic. The assembly reset handling code itself makes a single push of
-	  the return address, but the SoC-specific function (pm_s2ram_mark_check_and_clear) must be
-	  analyzed to determine the required stack size.
 
 config PM_S2RAM_CUSTOM_MARKING
 	bool "Use custom marking functions"