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author | Michael Brown | 2007-07-14 15:21:18 +0200 |
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committer | Michael Brown | 2007-07-14 15:21:18 +0200 |
commit | 95c07736cbc652f477a56857ed45382d7e4f3e69 (patch) | |
tree | 31f78d8e8b76ee78afcb88f7bc104d5bba52fca2 | |
parent | Kill off the enforced RX quota; it only seems to hurt on real hardware. (diff) | |
download | ipxe-95c07736cbc652f477a56857ed45382d7e4f3e69.tar.gz ipxe-95c07736cbc652f477a56857ed45382d7e4f3e69.tar.xz ipxe-95c07736cbc652f477a56857ed45382d7e4f3e69.zip |
Be more aggressive in attempts to enable A20, now that we have the
optimisation of only trying to do so when necessary.
-rw-r--r-- | src/arch/i386/Config | 9 | ||||
-rw-r--r-- | src/arch/i386/firmware/pcbios/gateA20.c | 78 |
2 files changed, 50 insertions, 37 deletions
diff --git a/src/arch/i386/Config b/src/arch/i386/Config index dc96e0af..436917f8 100644 --- a/src/arch/i386/Config +++ b/src/arch/i386/Config @@ -62,15 +62,6 @@ # Some systems do not have timer2 implemented. # If you have a RTC this will allow you to roughly calibrate # 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 diff --git a/src/arch/i386/firmware/pcbios/gateA20.c b/src/arch/i386/firmware/pcbios/gateA20.c index c424f123..8c4ccfad 100644 --- a/src/arch/i386/firmware/pcbios/gateA20.c +++ b/src/arch/i386/firmware/pcbios/gateA20.c @@ -22,25 +22,27 @@ enable data 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, Query_A20_Support = 0x2403 }; -#define CF ( 1 << 0 ) - -#ifndef IBM_L40 +/** + * 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. - */ + SLOW_DOWN_IO; + ( void ) inb ( K_RDWR ); + SLOW_DOWN_IO; } } -#endif /* IBM_L40 */ /** * Fast test to see if gate A20 is already set @@ -82,6 +84,8 @@ static int gateA20_is_set ( void ) { void gateA20_set ( void ) { static char reentry_guard = 0; unsigned int discard_a; + unsigned int scp_a; + int retries = 0; /* Avoid potential infinite recursion */ if ( reentry_guard ) @@ -92,31 +96,49 @@ void gateA20_set ( void ) { if ( gateA20_is_set() ) goto out; - /* Try INT 15 method first */ - __asm__ __volatile__ ( REAL_CODE ( "int $0x15" ) - : "=a" ( discard_a ) - : "a" ( Enable_A20 ) ); - if ( gateA20_is_set() ) - goto out; - - /* 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 */ - if ( gateA20_is_set() ) - 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; + } + } /* 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; } |