X-Git-Url: http://git.etherboot.org/gpxe.git/blobdiff_plain/80cc27cbc44cf6b692141840ab2ef7abf0a2c1a0..5bc6c0ca2f8d20f2fbacc1980fb86ac6dc694b68:/src/arch/i386/firmware/pcbios/gateA20.c?ds=sidebyside

diff --git a/src/arch/i386/firmware/pcbios/gateA20.c b/src/arch/i386/firmware/pcbios/gateA20.c
index cdc86685..1a71472d 100644
--- a/src/arch/i386/firmware/pcbios/gateA20.c
+++ b/src/arch/i386/firmware/pcbios/gateA20.c
@@ -1,7 +1,10 @@
-#include "realmode.h"
-#include "timer.h"
-#include "latch.h"
-#include "bios.h"
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdio.h>
+#include <realmode.h>
+#include <bios.h>
+#include <gpxe/io.h>
+#include <gpxe/timer.h>
 
 #define K_RDWR		0x60		/* keyboard data & cmds (read/write) */
 #define K_STATUS	0x64		/* keyboard status */
@@ -12,6 +15,7 @@
 
 #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
@@ -21,25 +25,69 @@
 					   enable data line
 					   disable clock line */
 
+#define SCP_A		0x92		/* System Control Port A */
+
 enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
 	Query_A20_Support = 0x2403 };
 
-#define CF ( 1 << 0 )
+enum a20_methods {
+	A20_UNKNOWN = 0,
+	A20_INT15,
+	A20_KBC,
+	A20_SCPA,
+};
 
-#ifndef IBM_L40
+#define A20_MAX_RETRIES		32
+#define A20_INT15_RETRIES	32
+#define A20_KBC_RETRIES		(2^21)
+#define A20_SCPA_RETRIES	(2^21)
+
+/**
+ * Drain keyboard controller
+ */
 static void empty_8042 ( void ) {
 	unsigned long time;
 
 	time = currticks() + TICKS_PER_SEC;	/* max wait of 1 second */
-	while ( ( inb ( K_CMD ) & K_IBUF_FUL ) &&
+	while ( ( inb ( K_CMD ) & ( K_IBUF_FUL | K_OBUF_FUL ) ) &&
 		currticks() < time ) {
-		/* Do nothing.  In particular, do *not* read from
-		 * K_RDWR, because that will drain the keyboard buffer
-		 * and lose keypresses.
-		 */
+		iodelay();
+		( void ) inb_p ( K_RDWR );
+		iodelay();
 	}
 }
-#endif	/* IBM_L40 */
+
+/**
+ * Fast test to see if gate A20 is already set
+ *
+ * @v retries		Number of times to retry before giving up
+ * @ret set		Gate A20 is set
+ */
+static int gateA20_is_set ( int retries ) {
+	static uint32_t test_pattern = 0xdeadbeef;
+	physaddr_t test_pattern_phys = virt_to_phys ( &test_pattern );
+	physaddr_t verify_pattern_phys = ( test_pattern_phys ^ 0x100000 );
+	userptr_t verify_pattern_user = phys_to_user ( verify_pattern_phys );
+	uint32_t verify_pattern;
+
+	do {
+		/* Check for difference */
+		copy_from_user ( &verify_pattern, verify_pattern_user, 0,
+				 sizeof ( verify_pattern ) );
+		if ( verify_pattern != test_pattern )
+			return 1;
+
+		/* Avoid false negatives */
+		test_pattern++;
+
+		iodelay();
+
+		/* Always retry at least once, to avoid false negatives */
+	} while ( retries-- >= 0 );
+
+	/* Pattern matched every time; gate A20 is not set */
+	return 0;
+}
 
 /*
  * Gate A20 for high memory
@@ -51,36 +99,75 @@ static void empty_8042 ( void ) {
  */
 void gateA20_set ( void ) {
 	static char reentry_guard = 0;
+	static int a20_method = A20_UNKNOWN;
 	unsigned int discard_a;
-	unsigned int flags;
+	unsigned int scp_a;
+	int retries = 0;
 
+	/* Avoid potential infinite recursion */
 	if ( reentry_guard )
 		return;
 	reentry_guard = 1;
 
-	__asm__ __volatile__ ( REAL_CODE ( "sti\n\t"
-					   "stc\n\t"
-					   "int $0x15\n\t"
-					   "pushfw\n\t"
-					   "popw %w0\n\t"
-					   "cli\n\t" )
-			       : "=r" ( flags ), "=a" ( discard_a )
-			       : "a" ( Enable_A20 ) );
-
-
-	if ( flags & CF ) {
-		/* INT 15 method failed, try alternatives */
-#ifdef	IBM_L40
-		outb(0x2, 0x92);
-#else	/* IBM_L40 */
-		empty_8042();
-		outb(KC_CMD_WOUT, K_CMD);
-		empty_8042();
-		outb(KB_SET_A20, K_RDWR);
-		empty_8042();
-#endif	/* IBM_L40 */
+	/* Fast check to see if gate A20 is already enabled */
+	if ( gateA20_is_set ( 0 ) )
+		goto out;
+
+	for ( ; retries < A20_MAX_RETRIES ; retries++ ) {
+		switch ( a20_method ) {
+		case A20_UNKNOWN:
+		case A20_INT15:
+			/* Try INT 15 method */
+			__asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
+					       : "=a" ( discard_a )
+					       : "a" ( Enable_A20 ) );
+			if ( gateA20_is_set ( A20_INT15_RETRIES ) ) {
+				DBG ( "Enabled gate A20 using BIOS\n" );
+				a20_method = A20_INT15;
+				goto out;
+			}
+			/* fall through */
+		case A20_KBC:
+			/* Try keyboard controller method */
+			empty_8042();
+			outb ( KC_CMD_WOUT, K_CMD );
+			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" );
+				a20_method = A20_KBC;
+				goto out;
+			}
+			/* fall through */
+		case A20_SCPA:
+			/* Try "Fast gate A20" method */
+			scp_a = inb ( SCP_A );
+			scp_a &= ~0x01; /* Avoid triggering a reset */
+			scp_a |= 0x02; /* Enable A20 */
+			iodelay();
+			outb ( scp_a, SCP_A );
+			iodelay();
+			if ( gateA20_is_set ( A20_SCPA_RETRIES ) ) {
+				DBG ( "Enabled gate A20 using "
+				      "Fast Gate A20\n" );
+				a20_method = A20_SCPA;
+				goto out;
+			}
+		}
 	}
 
+	/* Better to die now than corrupt memory later */
+	printf ( "FATAL: Gate A20 stuck\n" );
+	while ( 1 ) {}
+
+ out:
+	if ( retries )
+		DBG ( "%d attempts were required to enable A20\n",
+		      ( retries + 1 ) );
 	reentry_guard = 0;
 }