ich watchdog vs intel smm code

[Pegasus Mc Cleaft]

----- Original Message ----- 
From: "Andriy Gapon" <avg at icyb.net.ua>
To: <freebsd-hackers at freebsd.org>; <freebsd-acpi at freebsd.org>
Sent: Monday, January 19, 2009 12:11 PM
Subject: ich watchdog vs intel smm code


>
> Some time earlier I reported that ichwd driver doesn't produce any
> effect on my system with Intel DG33TL motherboard when watchdog timer is
> allowed to expire.
> I did some investigation and also discussed the issue with a maintainer
> of Linux iTCO_wdt driver, Wim Van Sebroeck. He told me that the issue is
> present on most of Intel motherboards with ICH9 chipset.
>
> All evidence seems to point in one direction - Intel SMM code.
> It seems that ICH9 always gets configured by BIOS to produce an SMI when
> a watchdog timer expires. Also, ICH watchdog has a logic to cause a
> reboot if its timer expires twice in a row, this is to avoid a potential
> hang in SMI handler.
> ICH9 allows SMI to be globally enabled and disabled. BIOS configures it
> to be enabled. Sometimes this bit is locked down (by BIOS), so it's not
> possible to change it, but sometimes it is not locked.
> So, if we globally disable SMI, then the watchdog in ICH9 does indeed
> cause a reboot. Evidently this happens after the timer expires twice in 
> row.
>
> My conclusion is that SMI handler installed by BIOS somehow acknowledges
> watchdog SMI (e.g. clears a certain status bit, or performs watchdog
> timer reload). But it doesn't execute any "corrective" action.
>
> My guess is there might some configuration (or some other form of
> massaging) that needs to be done in order to convince SMM code to
> perform a reboot upon watchdog SMI.
>
> It would be nice if we had some Intel insiders who could provide a
> glimpse into Intel SMM code logic with respect to the watchdog.
>
> Finally some technical details:
>
> NMI2SMI_EN and TCO_LOCK bits of TCO1_CNT are set 1:
> pmbase+0x0068: 0x1200     (TCO1_CNT)
>
> in SMI_EN register TCO_EN bit is 1, GBL_SMI_EN is 1, "End of SMI
> (EOS)" bit is 1 and (not sure if this matters) LEGACY_USB_EN is 1:
> pmbase+0x0030: 0x0000203b (SMI_EN)
>
> "No Reboot (NR)" bit of GCS register is zero:
> 0x3410: 0x00c01444

    I have a simmilar problem on my gigabyte motherboard (one of the X48 
ones), however, I believe the fault to be in hardware and not in firmware or 
software..

    Mentioned in the datasheet for the ICH9, the speaker pin is used as a 
configuration pin while reset it asserted. If a logic 1 is present on this 
pin when reset is deasserted, the ICH9 chip locks out the ability for 
software to enable the watchdog. With the ichwd driver for BSD, this 
condition is announced with a message like "Watchdog present, but disabled 
in BIOS".  (Well.. something close to that)

~Peg