TL;DR: On some motherboards with an Intel chipset, at least from Asus and Asrock, the hardware watchdog (linux driver iTCO-wdt) fails to reboot the system correctly (POST fails and leaves system unusable). Looking for people willing to test, in order to pinpoint the problem.
Background: I am looking for users of a desktop with a fairly recent Intel chipset, especially if one or several of the following conditions are satisfied: (1)the BIOS is written by AMI (American Megatrends), (2)the chipset is of the Intel 100 series or C230 series (a.k.a. "Sunrise Point", used for "Skylake" processors with an LGA1151 socket), and (3)the system is booting under UEFI (as opposed to legacy BIOS). The point of this test is to check whether the hardware watchdog included in these chipsets (and known in Intel parlance, this watchdog as the "TCO watchdog", where "TCO" stands for "Total Cost of Ownership") reboots the system properly or, as on my motherboard, places it in a broken state (POST fails, even when the reset button is later pressed, or even if the power button is pressed twice; the power supply needs to be disconnected for a few minutes to restore the system to a working state). This is a very serious bug, which could be due to the BIOS, the hardware, or Linux (I suspect the former, but it is conceivable that Linux could work around it). Do not perform this test unless you can disconnect the power supply! How to test: Boot a recent Linux kernel. Load the i2c-i801 and i2c-smbus modules. Then load the iTCO-wdt module. This should cause lines such as the following to appear in the kernel log (dmesg), indicating that Linux has detected the device: iTCO_wdt: Intel TCO WatchDog Timer Driver v1.11 iTCO_wdt: Found a Intel PCH TCO device (Version=4, TCOBASE=0x0400) iTCO_wdt: initialized. heartbeat=120 sec (nowayout=0) Make sure all your filesystems are unmounted or mounted read-only (on systemd, e.g.: systemctl isolate emergency.target ; sync ; echo u >> /proc/sysrq-trigger ; sync (and make sure "Emergency Remount complete" appears at the end of dmesg)). A /dev/watchdog device should have appeared. Then run cat >> /dev/watchdog and press enter twice. Do not interrupt (do not press control-C or control-D), just wait for a few minutes. After a certain time (twice the "heartbeat" value indicated by the kernel), the system will try to reboot. What interests me is whether the reboot succeeds (POST proceeds as normal, and OS restarts) or whether the system locks up (in which case you will need to power cycle it at the power supply unit level in order to restore it to normal). Please report (to me, to avoid spamming this list - I will post a summary) results along with information as to the hardware used: motherboard brand and model, BIOS vendor and date (dmidecode should give this information), UEFI or legacy boot, and any extension cards that might be used on the system (in particular, whether the system uses an integrated GPU or a separate graphics card). I am interested in both positive and negative results. Thanks in advance to all who are willing to test this! Xref: https://lkml.org/lkml/2016/9/8/641 https://www.reddit.com/r/linuxquestions/comments/51xad5/users_of_a_desktop_with_an_intel_chipset_could/ -- David A. Madore ( http://www.madore.org/~david/ )
