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On advice of hpa: be more patient with the KBC and SCPA methods; retry 

in a long loop before giving up on them.  Record method which worked
and default to that method on next attempt.
This commit is contained in:
Michael Brown 2007-07-14 20:56:12 +01:00
parent adf192f566
commit 26473105cd
1 changed files with 71 additions and 47 deletions
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118
src/arch/i386/firmware/pcbios/gateA20.c
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@ -24,11 +24,21 @@
#define SCP_A 0x92 /* System Control Port A */
#define A20_MAX_RETRIES 32
enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
Query_A20_Support = 0x2403 };
enum a20_methods {
A20_UNKNOWN = 0,
A20_INT15,
A20_KBC,
A20_SCPA,
};
#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
*/
@ -47,29 +57,32 @@ static void empty_8042 ( void ) {
/**
* 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 ( void ) {
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;
/* Check for difference */
copy_from_user ( &verify_pattern, verify_pattern_user, 0,
sizeof ( verify_pattern ) );
if ( verify_pattern != test_pattern )
return 1;
do {
/* Check for difference */
copy_from_user ( &verify_pattern, verify_pattern_user, 0,
sizeof ( verify_pattern ) );
if ( verify_pattern != test_pattern )
return 1;
/* Invert pattern and retest, just to be sure */
test_pattern ^= 0xffffffff;
copy_from_user ( &verify_pattern, verify_pattern_user, 0,
sizeof ( verify_pattern ) );
if ( verify_pattern != test_pattern )
return 1;
/* Avoid false negatives */
test_pattern++;
/* Pattern matched both times; gate A20 is not set */
SLOW_DOWN_IO;
/* Always retry at least once, to avoid false negatives */
} while ( retries-- >= 0 );
/* Pattern matched every time; gate A20 is not set */
return 0;
}
@ -83,6 +96,7 @@ static int gateA20_is_set ( void ) {
*/
void gateA20_set ( void ) {
static char reentry_guard = 0;
static int a20_method = A20_UNKNOWN;
unsigned int discard_a;
unsigned int scp_a;
int retries = 0;
@ -93,41 +107,51 @@ void gateA20_set ( void ) {
reentry_guard = 1;
/* Fast check to see if gate A20 is already enabled */
if ( gateA20_is_set() )
if ( gateA20_is_set ( 0 ) )
goto out;
for ( ; retries < A20_MAX_RETRIES ; retries++ ) {
/* Try INT 15 method first */
__asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
: "=a" ( discard_a )
: "a" ( Enable_A20 ) );
if ( gateA20_is_set() ) {
DBG ( "Enabled gate A20 using BIOS\n" );
goto out;
}
/* Try keyboard controller method */
empty_8042();
outb ( KC_CMD_WOUT, K_CMD );
empty_8042();
outb ( KB_SET_A20, K_RDWR );
empty_8042();
if ( gateA20_is_set() ) {
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;
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();
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 */
SLOW_DOWN_IO;
outb ( scp_a, SCP_A );
SLOW_DOWN_IO;
if ( gateA20_is_set ( A20_SCPA_RETRIES ) ) {
DBG ( "Enabled gate A20 using "
"Fast Gate A20\n" );
a20_method = A20_SCPA;
goto out;
}
}
}