Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 77 insertions, 0 deletions

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+===========================
+HPE iLO NMI Watchdog Driver
+===========================
+
+for iLO based ProLiant Servers
+==============================
+
+Last reviewed: 08/20/2018
+
+
+ The HPE iLO NMI Watchdog driver is a kernel module that provides basic
+ watchdog functionality and handler for the iLO "Generate NMI to System"
+ virtual button.
+
+ All references to iLO in this document imply it also works on iLO2 and all
+ subsequent generations.
+
+ Watchdog functionality is enabled like any other common watchdog driver. That
+ is, an application needs to be started that kicks off the watchdog timer. A
+ basic application exists in tools/testing/selftests/watchdog/ named
+ watchdog-test.c. Simply compile the C file and kick it off. If the system
+ gets into a bad state and hangs, the HPE ProLiant iLO timer register will
+ not be updated in a timely fashion and a hardware system reset (also known as
+ an Automatic Server Recovery (ASR)) event will occur.
+
+ The hpwdt driver also has the following module parameters:
+
+ ============  ================================================================
+ soft_margin   allows the user to set the watchdog timer value.
+               Default value is 30 seconds.
+ timeout       an alias of soft_margin.
+ pretimeout    allows the user to set the watchdog pretimeout value.
+               This is the number of seconds before timeout when an
+               NMI is delivered to the system. Setting the value to
+               zero disables the pretimeout NMI.
+               Default value is 9 seconds.
+ nowayout      basic watchdog parameter that does not allow the timer to
+               be restarted or an impending ASR to be escaped.
+               Default value is set when compiling the kernel. If it is set
+               to "Y", then there is no way of disabling the watchdog once
+               it has been started.
+ kdumptimeout  Minimum timeout in seconds to apply upon receipt of an NMI
+               before calling panic. (-1) disables the watchdog.  When value
+               is > 0, the timer is reprogrammed with the greater of
+               value or current timeout value.
+ ============  ================================================================
+
+ NOTE:
+       More information about watchdog drivers in general, including the ioctl
+       interface to /dev/watchdog can be found in
+       Documentation/watchdog/watchdog-api.rst and Documentation/IPMI.txt.
+
+ Due to limitations in the iLO hardware, the NMI pretimeout if enabled,
+ can only be set to 9 seconds.  Attempts to set pretimeout to other
+ non-zero values will be rounded, possibly to zero.  Users should verify
+ the pretimeout value after attempting to set pretimeout or timeout.
+
+ Upon receipt of an NMI from the iLO, the hpwdt driver will initiate a
+ panic. This is to allow for a crash dump to be collected.  It is incumbent
+ upon the user to have properly configured the system for kdump.
+
+ The default Linux kernel behavior upon panic is to print a kernel tombstone
+ and loop forever.  This is generally not what a watchdog user wants.
+
+ For those wishing to learn more please see:
+	Documentation/admin-guide/kdump/kdump.rst
+	Documentation/admin-guide/kernel-parameters.txt (panic=)
+	Your Linux Distribution specific documentation.
+
+ If the hpwdt does not receive the NMI associated with an expiring timer,
+ the iLO will proceed to reset the system at timeout if the timer hasn't
+ been updated.
+
+--
+
+ The HPE iLO NMI Watchdog Driver and documentation were originally developed
+ by Tom Mingarelli.