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Be more aggressive in attempts to enable A20, now that we have the

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optimisation of only trying to do so when necessary.
This commit is contained in:
Michael Brown
2007-07-14 14:21:18 +01:00
parent 8624fdc445
commit 95c07736cb
2 changed files with 50 additions and 37 deletions
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9
src/arch/i386/Config
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@@ -62,15 +62,6 @@
# Some systems do not have timer2 implemented. # Some systems do not have timer2 implemented.
# If you have a RTC this will allow you to roughly calibrate # If you have a RTC this will allow you to roughly calibrate
# it using outb instructions. # it using outb instructions.
# -DIBM_L40
# This option uses the 0x92 method of controlling
# A20 instead of the traditional method of using the
# keyboard controller. An explanation of A20 is here:
# http://www.win.tue.nl/~aeb/linux/kbd/A20.html
# This occurs on MCA, EISA and some embedded boards,
# and sometimes with the Fast Gate A20 option on some
# BIOSes.
# Enable this only if you are sure of what you are doing.
# #
# Extended cpu options # Extended cpu options

78
src/arch/i386/firmware/pcbios/gateA20.c
View File

@@ -22,25 +22,27 @@
enable data line enable data line
disable clock line */ disable clock line */
#define SCP_A 0x92 /* System Control Port A */
#define A20_MAX_RETRIES 32
enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402, enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
Query_A20_Support = 0x2403 }; Query_A20_Support = 0x2403 };
#define CF ( 1 << 0 ) /**
* Drain keyboard controller
#ifndef IBM_L40 */
static void empty_8042 ( void ) { static void empty_8042 ( void ) {
unsigned long time; unsigned long time;
time = currticks() + TICKS_PER_SEC; /* max wait of 1 second */ 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 ) { currticks() < time ) {
/* Do nothing. In particular, do *not* read from SLOW_DOWN_IO;
* K_RDWR, because that will drain the keyboard buffer ( void ) inb ( K_RDWR );
* and lose keypresses. SLOW_DOWN_IO;
*/
} }
} }
#endif /* IBM_L40 */
/** /**
* Fast test to see if gate A20 is already set * Fast test to see if gate A20 is already set
@@ -82,6 +84,8 @@ static int gateA20_is_set ( void ) {
void gateA20_set ( void ) { void gateA20_set ( void ) {
static char reentry_guard = 0; static char reentry_guard = 0;
unsigned int discard_a; unsigned int discard_a;
unsigned int scp_a;
int retries = 0;
/* Avoid potential infinite recursion */ /* Avoid potential infinite recursion */
if ( reentry_guard ) if ( reentry_guard )
@@ -92,31 +96,49 @@ void gateA20_set ( void ) {
if ( gateA20_is_set() ) if ( gateA20_is_set() )
goto out; goto out;
/* Try INT 15 method first */ for ( ; retries < A20_MAX_RETRIES ; retries++ ) {
__asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
: "=a" ( discard_a ) /* Try INT 15 method first */
: "a" ( Enable_A20 ) ); __asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
if ( gateA20_is_set() ) : "=a" ( discard_a )
goto out; : "a" ( Enable_A20 ) );
if ( gateA20_is_set() ) {
/* INT 15 method failed, try alternatives */ DBG ( "Enabled gate A20 using BIOS\n" );
#ifdef IBM_L40 goto out;
outb(0x2, 0x92); }
#else /* IBM_L40 */
empty_8042(); /* Try keyboard controller method */
outb(KC_CMD_WOUT, K_CMD); empty_8042();
empty_8042(); outb ( KC_CMD_WOUT, K_CMD );
outb(KB_SET_A20, K_RDWR); empty_8042();
empty_8042(); outb ( KB_SET_A20, K_RDWR );
#endif /* IBM_L40 */ empty_8042();
if ( gateA20_is_set() ) if ( gateA20_is_set() ) {
goto out; DBG ( "Enabled gate A20 using keyboard controller\n" );
goto out;
}
/* Try "Fast gate A20" method */
scp_a = inb ( SCP_A );
scp_a &= ~0x01; /* Avoid triggering a reset */
scp_a |= 0x02; /* Enable A20 */
SLOW_DOWN_IO;
outb ( scp_a, SCP_A );
SLOW_DOWN_IO;
if ( gateA20_is_set() ) {
DBG ( "Enabled gate A20 using Fast Gate A20\n" );
goto out;
}
}
/* Better to die now than corrupt memory later */ /* Better to die now than corrupt memory later */
printf ( "FATAL: Gate A20 stuck\n" ); printf ( "FATAL: Gate A20 stuck\n" );
while ( 1 ) {} while ( 1 ) {}
out: out:
if ( retries )
DBG ( "%d attempts were required to enable A20\n",
( retries + 1 ) );
reentry_guard = 0; reentry_guard = 0;
} }