doc/kernel-parameters.txt: add early_ioremap_debug

Add description of early_ioremap_debug kernel parameter.

Signed-off-by: Mark Salter <>
Cc: Borislav Petkov <>
Cc: Catalin Marinas <>
Cc: Dave Young <>
Cc: H. Peter Anvin <>
Cc: Will Deacon <>
Cc: Ingo Molnar <>
Cc: Thomas Gleixner <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bc34785..b6c67d5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -884,6 +884,11 @@
 			Enable debug messages at boot time.  See
 			Documentation/dynamic-debug-howto.txt for details.
+	early_ioremap_debug [KNL]
+			Enable debug messages in early_ioremap support. This
+			is useful for tracking down temporary early mappings
+			which are not unmapped.
 	earlycon=	[KNL] Output early console device and options.