Kontron AT8404 - Manual (Page 67)

Software Description
54 AT8404 User Guide
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4.3 IPMI Firmware
The Unit Computer communicates with the Intelligent Platform Management Controller (IPMC) using the
Keyboard Controller Style (KCS) interface. The bootloader is able to communicate with the IPMC, e.g. for
POST error logging purposes and fault resilient purposes.
The memory subsystem of the IPMC consists of an integrated flash memory to hold the IPMC operation code
and integrated RAM for data. The field replaceable unit (FRU) inventory information is stored in the nonvol-
atile memory on an EEPROM connected via a local I2C interface to the IPMC micro controller. It is possible to
store up to 4 KBytes within the FRU inventory information. Communication over IPMB bus to the ShMC
ensures that ‘post-mortem’ logging information is available even if the main processor becomes disabled.
The IPMC provides six I2C bus connections. Two are used as the redundant IPMB bus connections to the back-
plane, one is used for IPMB-L bus with AMC modules, one for the connection to a managed RTM, one for the
Base Board and one is for local EEPROM storage.
If an IPMB bus fault or IPMC failure occurs, IPMB isolators are used to switch from and isolate the backplane/
system IPMB bus from the faulted Carrier Board. If possible, the IPMC activates the redundant IPMB bus to
re-establish system management communication to report the fault.
The onboard DC voltage, current, and temperature sensors are monitored by the IPMC micro controller con-
tinuously. The IPMC will log an event into the ShMC’s System Event Log (SEL) if any of the thresholds are
exceeded.
To increase the reliability of the AT8404 management subsystem, an external watchdog supervisor for the
IPMC is implemented. The IPMC strobes the external watchdog at two-second intervals to ensure continuity
of operation of the board’s management subsystem. If the IPMC ceases to strobe the watchdog supervisor
for more than six seconds, the watchdog isolates the IPMC from the IPMBs and resets the IPMC. The watch-
dog supervisor does not reset the payload power and the restart of the IPMC will not affect the payload and
will restore the previous Hot Swap state and power level negotiated with the ShMC. The external watchdog
supervisor is not configurable and must not be confused with the IPMI v1.5 watchdog timer commands.
4.3.1 Sensor Data Record (SDR)
Every sensor on the Base Board is associated with a Sensor Data Record (SDR). Sensor Data Records contain
information about the sensor's identification such as sensor type, sensor name, sensor unit. SDR also con-
tain the configuration of a specific sensor such as threshold/hysteresis and event generation capabilities
that specifies sensor behaviour. Some field of the sensor SDR are configurable through IPMI v1.5 commands
and are set to built-in initial value.
The AT8404 management controller supports sensor devices and uses the IPMI dynamic sensor population
feature of IPMI v1.5 to merge the AMC hot swap sensor with the AT8404 sensors population. AMC hot swap
events indicated by this sensor are passed to the ShMC. Additionally, the IPMC updates the sensor popula-
tion change indicator timestamp accessible through the Get Device SDR Info command to remain compliant
to IPMI v1.5.
All SDRs can be queried using Device SDR commands. Base Board sensors that have been implemented are
listed below.