[PATCH] A20 tweak for AMD Elan

The A20 code needs a slight tweak to work on AMD Elans.
Original patch from Robert Schwebel

arch/i386/boot/setup.S

@@ -42,6 +42,9 @@
  * if CX/DX have been changed in the e801 call and if so use AX/BX .
  * Michael Miller, April 2001 <michaelm@mjmm.org>
  *
+ * New A20 code ported from SYSLINUX by H. Peter Anvin. AMD Elan bugfixes
+ * by Robert Schwebel, December 2001 <robert@schwebel.de>
+ *
  */
 
 #include <linux/config.h>
@@ -651,8 +654,19 @@ end_move_self:					# now we are at the right place
 #
 # Enable A20.  This is at the very best an annoying procedure.
 # A20 code ported from SYSLINUX 1.52-1.63 by H. Peter Anvin.
+# AMD Elan bug fix by Robert Schwebel.
 #
 
+#if defined(CONFIG_MELAN)
+	movb $0x02, %al			# alternate A20 gate
+	outb %al, $0x92			# this works on SC410/SC520
+a20_elan_wait:
+	call a20_test
+	jz a20_elan_wait
+	jmp a20_done
+#endif
+
+
 A20_TEST_LOOPS		=  32		# Iterations per wait
 A20_ENABLE_LOOPS	= 255		# Total loops to try