From 26473105cd83ebb604b433a7c3a04b342cdd9991 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Sat, 14 Jul 2007 20:56:12 +0100 Subject: [PATCH] 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. --- src/arch/i386/firmware/pcbios/gateA20.c | 118 ++++++++++++++---------- 1 file changed, 71 insertions(+), 47 deletions(-) diff --git a/src/arch/i386/firmware/pcbios/gateA20.c b/src/arch/i386/firmware/pcbios/gateA20.c index 8c4ccfad..66b4da18 100644 --- a/src/arch/i386/firmware/pcbios/gateA20.c +++ b/src/arch/i386/firmware/pcbios/gateA20.c @@ -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; + } } }