arm64:add busy wait flag

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

arch/arm64/Kconfig

@@ -136,6 +136,17 @@ config ARCH_SINGLE_SECURITY_STATE
 		GIC or other ARM architecture feature will with different
 		configure
 
+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

@@ -207,6 +207,12 @@ 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;
+  *address = 1;
+  up_flush_dcache((uintptr_t)address, sizeof(address));
+#endif
+
   arm64_start_cpu(cpu);
 
   return 0;

arch/arm64/src/common/arm64_head.S

@@ -144,6 +144,16 @@ real_start:
     cmp    x1, #0
     beq    primary_core
 
+    /* Wait until cpu0 notify */
+
+#ifdef CONFIG_ARM64_SMP_BUSY_WAIT
+    ldr    x2, =CONFIG_ARM64_SMP_BUSY_WAIT_FLAG_ADDR
+1:
+    ldr    x3, [x2, #0]
+    cmp    x3, #0
+    beq    1b
+#endif
+
     /* we can now load our stack pointer value and move on */
 
     ldr    x24, =g_cpu_idlestackalloc