Re: 2.6 kernel won't reboot on AMD system - 8042 problem?

["David N. Welton" <davidw@eidetix.com>]

[ Please CC replies to me. ]

David N. Welton wrote:

> Before you hit reply or erase, no, I'm not talking about the machine not
> getting past the BIOS check complaining that there is no keyboard present.
> 
> Kernel 2.6.7
> 
> model name      : AMD Athlon(tm) XP 2400+
> 
> motherboard: http://www.ecsusa.com/products/km400-m2.html
> 
> ... not sure what else might be useful... apci=off added to boot
> options.  Preemptive kernel.
> 
> In any case, the machine in question does not reboot.  I traced the
> problem down to the mach_reboot but it doesn't get past those assembly
> instructions.  Things do seem to work alright if a keyboard is
> installed.  Otherwise, the machine just sits there, no longer responsive
> to pings or anything else.

....

> any ideas on what parts of the kernel to look at in order to determine
> what is causing this?  I need to fix it, and I don't know where to start 
> looking.

By putting a series of 'crashme/reboot' calls into the kernel, I 
narrowed a possibl cause of it down to this bit of code in 
drivers/input/serio.c:753

/*
  * Write CTR back.
  */

	if (i8042_command(&i8042_ctr, I8042_CMD_CTL_WCTR)) {
		printk(KERN_ERR "i8042.c: Can't write CTR while initializing i8042.\n");
		return -1;
	}

If I do the reboot instructions before this, it reboots fine. 
Afterwards, and it just sits there, no reboot.

Any ideas what to think/look for/do?

Sascha, to see if your problem is the same as mine, you might try 
putting this bit of code before the above call:

	{
	    static struct
	    {
		unsigned short       size __attribute__ ((packed));
		unsigned long long * base __attribute__ ((packed));
	    } no_idt = { 0, 0 };

	    /* That didn't work - force a triple fault.. */
	    __asm__ __volatile__("lidt %0": :"m" (no_idt));
	    __asm__ __volatile__("int3");
	}

It will cause your machine to reboot before it's even finished booting, 
so don't do it with your only available kernel!

Thanks,
-- 
David N. Welton
davidw@eidetix.com