diff options
Diffstat (limited to 'contrib/syslinux-4.02/gpxe/src/arch/i386/firmware/pcbios/gateA20.c')
| -rw-r--r-- | contrib/syslinux-4.02/gpxe/src/arch/i386/firmware/pcbios/gateA20.c | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/gpxe/src/arch/i386/firmware/pcbios/gateA20.c b/contrib/syslinux-4.02/gpxe/src/arch/i386/firmware/pcbios/gateA20.c new file mode 100644 index 0000000..1a71472 --- /dev/null +++ b/contrib/syslinux-4.02/gpxe/src/arch/i386/firmware/pcbios/gateA20.c @@ -0,0 +1,176 @@ +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 */ +#define K_CMD 0x64 /* keybd ctlr command (write-only) */ + +#define K_OBUF_FUL 0x01 /* output buffer full */ +#define K_IBUF_FUL 0x02 /* input buffer full */ + +#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 + disable clock line */ +#define KB_UNSET_A20 0xdd /* enable A20, + enable output buffer full interrupt + 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 }; + +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 + */ +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 | K_OBUF_FUL ) ) && + currticks() < time ) { + iodelay(); + ( void ) inb_p ( K_RDWR ); + iodelay(); + } +} + +/** + * 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 + * + * Note that this function gets called as part of the return path from + * librm's real_call, which is used to make the int15 call if librm is + * being used. To avoid an infinite recursion, we make gateA20_set + * return immediately if it is already part of the call stack. + */ +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; + + /* Avoid potential infinite recursion */ + if ( reentry_guard ) + return; + reentry_guard = 1; + + /* 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; +} + +void gateA20_unset ( void ) { + /* Not currently implemented */ +} |