arm64: remove busy wait flag

Replace CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR with global variable g_smp_busy_wait_flag for
SMP CPU synchronization. This improves flexibility over fixed memory addresses and aligns
with standard kernel variable patterns for multi-core startup.

Signed-off-by: hujun5 <hujun5@xiaomi.com>

arch/arm64/Kconfig

@@ -217,17 +217,6 @@ config ARM64_TBI
 	bool "Top Byte Ignore support"
 	default n
 
-config ARM64_SMP_BUSY_WAIT
-	bool "Busy wait when SMP boot"
-	default n
-	depends on SMP
-	---help---
-		Enables busy wait when SMP boot
-
-config ARM64_SMP_BUSY_WAIT_FLAG_ADDR
-	hex "Busy wait flag address"
-	depends on ARM64_SMP_BUSY_WAIT
-
 config ARCH_HAVE_EL3
 	bool
 	default n

arch/arm64/src/common/arm64_cpustart.c

@@ -76,6 +76,8 @@ uint64_t *const g_cpu_int_stacktop[CONFIG_SMP_NCPUS] =
 #endif /* CONFIG_SMP_NCPUS > 1 */
 };
 
+uint32_t g_smp_busy_wait_flag;
+
 #ifdef CONFIG_ARM64_DECODEFIQ
 uint64_t *const g_cpu_int_fiq_stacktop[CONFIG_SMP_NCPUS] =
 {
@@ -198,8 +200,8 @@ int up_cpu_start(int cpu)
   sched_note_cpu_start(this_task(), cpu);
 #endif
 
-#ifdef CONFIG_ARM64_SMP_BUSY_WAIT
-  uint32_t *address = (uint32_t *)CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR;
+#ifdef CONFIG_SMP
+  uint32_t *address = &g_smp_busy_wait_flag;
   *address = 1;
   up_flush_dcache((uintptr_t)address, (uintptr_t)address + sizeof(address));
 #endif

arch/arm64/src/common/arm64_head.S

@@ -143,13 +143,11 @@ real_start:
 
     /* Wait until cpu0 notify */
 
-#ifdef CONFIG_ARM64_SMP_BUSY_WAIT
-    ldr    x2, =CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR
+    ldr    x2, =g_smp_busy_wait_flag
 1:
-    ldr    x3, [x2, #0]
-    cmp    x3, #0
+    ldr    w3, [x2, #0]
+    cmp    w3, #0
     beq    1b
-#endif
 
     /* we can now load our stack pointer value and move on */
 

boards/arm64/fvp-v8r/fvp-armv8r/configs/nsh_smp/defconfig

@@ -14,8 +14,6 @@ CONFIG_ARCH_CHIP_FVP_ARMV8R=y
 CONFIG_ARCH_CHIP_FVP_R82=y
 CONFIG_ARCH_EARLY_PRINT=y
 CONFIG_ARCH_INTERRUPTSTACK=4096
-CONFIG_ARM64_SMP_BUSY_WAIT=y
-CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR=0x4000000
 CONFIG_ARM64_STRING_FUNCTION=y
 CONFIG_BUILTIN=y
 CONFIG_DEBUG_ASSERTIONS=y

boards/arm64/fvp-v8r/fvp-armv8r/configs/pnsh_smp/defconfig

@@ -18,8 +18,6 @@ CONFIG_ARCH_INTERRUPTSTACK=4096
 CONFIG_ARCH_KERNEL_STACK=y
 CONFIG_ARCH_KERNEL_STACKSIZE=8192
 CONFIG_ARCH_USE_MPU=y
-CONFIG_ARM64_SMP_BUSY_WAIT=y
-CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR=0x400000
 CONFIG_ARM64_STRING_FUNCTION=y
 CONFIG_BUILD_PROTECTED=y
 CONFIG_BUILTIN=y

boards/arm64/fvp-v8r/fvp-armv8r/scripts/dramboot.ld

@@ -59,9 +59,6 @@ SECTIONS
 
   .bss : {                     /* BSS */
        _sbss = . ;
-#if defined(CONFIG_SMP) && defined(CONFIG_ARM64_SMP_BUSY_WAIT)
-       . = . + 0x4;          /* Busy Wait Flag */
-#endif
        *(.bss*)
        . = ALIGN(4096);
        _ebss = .;