Date: Wed, 2 Jun 2004 09:36:20 -0700 (PDT) From: Nate Lawson <nate@root.org> To: Poul-Henning Kamp <phk@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/boot/i386/boot2 boot1.S Message-ID: <20040602093149.D35427@root.org> In-Reply-To: <20040602093847.D53A516A520@hub.freebsd.org> References: <20040602093847.D53A516A520@hub.freebsd.org>
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On Wed, 2 Jun 2004, Poul-Henning Kamp wrote: > phk 2004/06/02 02:38:33 PDT > > FreeBSD src repository > > Modified files: > sys/boot/i386/boot2 boot1.S > Log: > Some embedded platforms have no keyboard controller. Give up waiting > for it to react after a timeout. > > Revision Changes Path > 1.28 +11 -4 src/sys/boot/i386/boot2/boot1.S > > --- src/sys/boot/i386/boot2/boot1.S:1.27 Fri May 14 13:29:29 2004 > +++ src/sys/boot/i386/boot2/boot1.S Wed Jun 2 02:38:32 2004 > @@ -197,13 +197,16 @@ > xorb %al,%al # Zero assumed bss from > rep # the end of boot2.bin > stosb # up to 0x10000 > - callw seta20 # Enable A20 > - jmp start+MEM_JMP-MEM_ORG # Start BTX > + By removing the callw/retw and moving the jmp to the end, A20 enable can't be called as a subroutine from elsewhere. Will it be needed elsewhere? > /* > * Enable A20 so we can access memory above 1 meg. > + * Use the zero-valued %cx as a timeout for embedded hardware which do not > + * have a keyboard controller. > */ > seta20: cli # Disable interrupts > -seta20.1: inb $0x64,%al # Get status Should be a "movw TIMEOUT, %cx" here. (Or whatever the timeout constant is.) > +seta20.1: dec %cx # Timeout? > + jz seta20.3 # Yes > + inb $0x64,%al # Get status > testb $0x2,%al # Busy? > jnz seta20.1 # Yes > movb $0xd1,%al # Command: Write -Nate
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