[coreboot] localizing resets

Jeremy Jackson jerj at coplanar.net
Wed Apr 16 18:10:01 CEST 2008

Slightly related to the TCO timer issue, is that of shotgun approach vs
localized resets.  TCO timer is just a subset of the "bigiron" features
vendors put on their boards.  Is global reset an obstacle to using them?

I'm reminded of the Machine Check registers.  Linux has a boot option,
mce=bootlog, to enable reading these when linux starts, to get info
regarding the last reboot, if caused by a machine check, since it's
likely that the previous generation couldn't log (to disk) in the MCE

Linux's mce= defaults to ignoring the register contents at startup,
since many BIOS are reset-happy.  I bet there's places in Coreboot that
do this, like the hypertransport (but I don't know of registers that
matter) for example.

There are other registers that survive localized (CPU only or other
scopes) resets vs power on reset (global), 

The Intel 845 datasheet mentions that this depends on the board being
wired correctly.  The common practice of OR-ing the power-on reset
(power-good) signals with the front panel reset, defeats many of these

Power management has made fixing some of that a requirement, dividing a
system up into many power wells and reset domains, but there's bound to
be boards made that just don't care. (I hope mine isn't one of them)

I'm eyeing Cisco's feature that tells you the source of the last reset,
power-on, vs firmware monitor cmd, vs others.

Does anyone's hareware flag a TCO reset so the next generation can tell
that's why it was booted?

Jeremy Jackson
Coplanar Networks
jerj at coplanar.net

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