x86: coreboot: Control I/O port 0xb2 writing via device tree

Writing 0xcb to I/O port 0xb2 (Advanced Power Management Control) causes
U-Boot to hang on QEMU q35 target. We introduce a config option in the
device tree "u-boot,no-apm-finalize" under /config node if we don't want
to do that.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/coreboot/coreboot.c

@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <fdtdec.h>
 #include <netdev.h>
 #include <asm/io.h>
 #include <asm/msr.h>
@@ -74,9 +75,14 @@ void board_final_cleanup(void)
 		mtrr_close(&state);
 	}
 
-	/* Issue SMI to Coreboot to lock down ME and registers */
-	printf("Finalizing Coreboot\n");
-	outb(0xcb, 0xb2);
+	if (!fdtdec_get_config_bool(gd->fdt_blob, "u-boot,no-apm-finalize")) {
+		/*
+		 * Issue SMI to coreboot to lock down ME and registers
+		 * when allowed via device tree
+		 */
+		printf("Finalizing coreboot\n");
+		outb(0xcb, 0xb2);
+	}
 }
 
 int misc_init_r(void)

arch/x86/dts/qemu-x86_q35.dts

@@ -15,6 +15,7 @@
 
 	config {
 		silent_console = <0>;
+		u-boot,no-apm-finalize;
 	};
 
 	chosen {