Hi, Oh, actually a20 of macbook can be disabled with fast a20 port 92. However, the current a20 code do the keyboard controller test before trying port 92, which cause it to hang. To fix it, I only need to adjust the order of tests.
-- Bean
diff --git a/kern/i386/pc/startup.S b/kern/i386/pc/startup.S index 9542978..9752828 100644 --- a/kern/i386/pc/startup.S +++ b/kern/i386/pc/startup.S @@ -368,9 +368,32 @@ gate_a20_try_bios: popl %ebp call gate_a20_check_state cmpb %al, %dl - jnz gate_a20_try_keyboard_controller + jnz gate_a20_try_system_control_port_a ret +gate_a20_try_system_control_port_a: + /* + * In macbook, the keyboard test would hang the machine, so we move + * this forward. + */ + /* fourth, try the system control port A */ + inb $0x92 + andb $(~0x03), %al + testb %dl, %dl + jz 6f + orb $0x02, %al +6: outb $0x92 + + /* When turning off Gate A20, do not check the state strictly, + because a failure is not fatal usually, and Gate A20 is always + on some modern machines. */ + testb %dl, %dl + jz 7f + call gate_a20_check_state + cmpb %al, %dl + jnz gate_a20_try_keyboard_controller +7: ret + gate_a20_flush_keyboard_buffer: inb $0x64 andb $0x02, %al @@ -409,28 +432,9 @@ gate_a20_try_keyboard_controller: call gate_a20_check_state cmpb %al, %dl - jnz gate_a20_try_system_control_port_a - ret - -gate_a20_try_system_control_port_a: - /* fourth, try the system control port A */ - inb $0x92 - andb $(~0x03), %al - testb %dl, %dl - jz 6f - orb $0x02, %al -6: outb $0x92 - - /* When turning off Gate A20, do not check the state strictly, - because a failure is not fatal usually, and Gate A20 is always - on some modern machines. */ - testb %dl, %dl - jz 7f - call gate_a20_check_state - cmpb %al, %dl /* everything failed, so restart from the beginning */ jnz gate_a20_try_bios -7: ret + ret gate_a20_check_state: /* iterate the checking for a while */
_______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
