diff --git a/common/main.c b/common/main.c
index 4b4504557f6..794d4a46b97 100644
--- a/common/main.c
+++ b/common/main.c
@@ -5,7 +5,8 @@
  */
 
 /* #define	DEBUG	*/
-
+#include <asm/io.h>
+#include <asm/system.h>
 #include <autoboot.h>
 #include <button.h>
 #include <bootstage.h>
@@ -44,6 +45,26 @@ void main_loop(void)
 {
 	const char *s;
 
+	/* TEMPORARY bring-up diagnostics (krane Round 26) — do not upstream:
+	 * light-gray band = main_loop entered; U-Boot init fully done. */
+	{
+		u32 base = readl((void __iomem *)0x14008f40);
+
+		if (base >= 0x40000000) {
+			u32 *p = (u32 *)(uintptr_t)(base + 900ULL * 4800);
+			int i;
+
+			if (dcache_status())
+				mmu_map_region(base, 0x8ca000, false);
+			for (i = 0; i < 40 * 1200; i++)
+				p[i] = 0x00c0c0c0;
+			if (dcache_status())
+				flush_dcache_range((uintptr_t)p,
+						   (uintptr_t)(p + 40 * 1200));
+		}
+	}
+	/* end TEMPORARY diagnostics */
+
 	bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");
 
 	if (IS_ENABLED(CONFIG_VERSION_VARIABLE))
diff --git a/configs/mt8183_kukui_krane_defconfig b/configs/mt8183_kukui_krane_defconfig
index 7dc9bc4c453..df0d3221a16 100644
--- a/configs/mt8183_kukui_krane_defconfig
+++ b/configs/mt8183_kukui_krane_defconfig
@@ -74,6 +74,7 @@ CONFIG_DM_SERIAL=y
 CONFIG_DEBUG_UART_ANNOUNCE=y
 CONFIG_MTK_SERIAL=y
 CONFIG_WDT=y
+# CONFIG_WATCHDOG_AUTOSTART is not set
 CONFIG_WDT_MTK=y
 # CONFIG_RANDOM_UUID is not set
 # CONFIG_REGEX is not set