[coreboot] [PATCH] Halt TCO timer on Intel 3100 chipset

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sun Mar 30 19:50:25 CEST 2008

On 30.03.2008 16:18, joe at smittys.pointclark.net wrote:
> Quoting Ed Swierk <eswierk at arastra.com>:
>> On Sat, Mar 29, 2008 at 5:20 PM,  <joe at smittys.pointclark.net> wrote:
>>> After thinking about it.....
>>> What are the advantages of disabling the TCO timer (besides
>>> rebooting)? Doesn't the system need this to run properly? By setting
>>> the no reboot the timer is still running....does it need to be?
>> The point of the TCO timer is to let a system recover automatically by
>> sending an interrupt and then rebooting if the OS crashes. While
>> operating systems can crash for all sorts of reasons, coreboot code
>> doesn't generally crash unless there's a hardware failure or
>> misconfiguration that will not correct itself by rebooting. Thus it
>> makes sense to disable the timer in coreboot and let a TCO-aware
>> payload re-enable it.
>> The TCO timer has no other purpose that I'm aware of, so it doesn't
>> matter whether coreboot neuters its effect by setting NO_REBOOT or
>> halts it completely by setting TCO_TMR_HALT. Leaving the timer running
>> still causes an interrupt to occur on timeout, but I think it's a
>> no-op unless the OS is paying attention.
>> This document explains the TCO timer in more detail:
>> ftp://download.intel.com/design/chipsets/applnots/29227301.pdf.
> Thanks for the explanation Ed. That makes perfect sense.

Please halt the timer completely if possible. We are not really prepared
to handle interrupts in coreboot.


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