Computer hangs on reboot

[John Baldwin]

On Saturday 02 June 2007 12:12:14 am Andrey Shuvikov wrote:
> On 5/29/07, Andrey Shuvikov <mr.hyro at gmail.com> wrote:
> > On 5/29/07, John Baldwin <jhb at freebsd.org> wrote:
> > > On Saturday 26 May 2007 01:14:52 pm Andrey Shuvikov wrote:
> > > > I tried to add some debug output to cpu_reset_real() code:
> > > >
> > > >   printf("cpu_reset_real(): before keyboard reset\n");
> > > >   outb(IO_KBD + 4, 0xFE);
> > > >   printf("cpu_reset_real(): after keyboard reset\n");
> > > >
> > > > The last two lines I see on the screen when I try to reboot are:
> > > >
> > > > cpu_reset_real(): before keyboard reset
> > > > c
> > > >
> > > > So the computer is halted but doesn't go to reboot.
> > >
> > > So what if you disable the keyboard reset and let the other methods 
happen?
> > >
> > > --
> > > John Baldwin
> > >
> >
> > I tried to set BROKEN_KEYBOARD_RESET option but nothing changed
> > (except that I didn't see these debugging messages, obviously). Is it
> > possible that keyboard controller issues the reset signal but the CPU
> > waits for something? Or reset pin is disabled somehow?
> >
> 
> Tried to investigate further... Added code to print keyboard
> controller output port to make sure A20 is open. Got 0x0B. Does it
> mean that A20 is really open? If A20 is controlled by some kind of
> "Fast A20" option, will keyboard controller still show the right
> status? And what else can I check?

I believe I/O port 0x92 can gate A20 as well, and that it is only open if both 
say it is open.  Grab a datasheet for an ICH from developer.intel.com to find 
more details on port 0x92.

-- 
John Baldwin