[a20] Send a null command to the KBC after changing A20
[people/mdeck/gpxe.git] / src / arch / i386 / firmware / pcbios / gateA20.c
index 2caac89..a14e341 100644 (file)
@@ -12,6 +12,7 @@
 
 #define KC_CMD_WIN     0xd0            /* read  output port */
 #define KC_CMD_WOUT    0xd1            /* write output port */
+#define KC_CMD_NULL    0xff            /* null command ("pulse nothing") */
 #define KB_SET_A20     0xdf            /* enable A20,
                                           enable output buffer full interrupt
                                           enable data line
@@ -130,6 +131,8 @@ void gateA20_set ( void ) {
                        empty_8042();
                        outb ( KB_SET_A20, K_RDWR );
                        empty_8042();
+                       outb ( KC_CMD_NULL, K_CMD );
+                       empty_8042();
                        if ( gateA20_is_set ( A20_KBC_RETRIES ) ) {
                                DBG ( "Enabled gate A20 using "
                                      "keyboard controller\n" );