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68 MPCMM0001 Chassis Management Module Software Technical Product Specification
Power and Hot Swap Management
Power and Hot Swap Management 7
The CMM is responsible for the management of FRU hot-swap activities. The CMM listens to
FRU hot-swap SEL messages from IPMI devices and distributes power to each FRU after
negotiating with the respective IPMI device fronting the FRU. The CMM also manages the shelf-
wide power budget. The CMM also polls IPMI devices to get the status of each FRU fronted by the
IPMI device. The CMM uses shelf FRU information to guarantee power-up sequence delays
between boards.
Once the CMM receives the shelf FRU information on power budget and power sequence delays, it
is ready to service FRU hot-swap requests from respective IPMI devices.
7.1 Hot Swap States
The CMM defines the hot swap status of a FRU as being in one of eight states. CMM
documentation often refers to only the letter/number designation of that state (M0 - M7). Here is a
list of what each of those states means:
• "State M0 - Not Installed"
• "State M1 - Inactive"
• "State M2 - Activation Request"
• "State M3 - Activation In Progress"
• "State M4 - Active"
• "State M5 - Deactivation Request"
• "State M6 - Deactivation In Progress"
• "State M7 - Communication Lost"
7.2 FRU Insertion
When the CMM receives a request that a FRU is ready to activate, it will compute the FRU’s
power, get the power levels, and check the available power budget.
The Set_Power_Level command will be sent only when the necessary power budget, from each of
the redundant power feeds, is available to satisfy FRU's desired power level. If a FRU can't be
activated at the time of the request, it should remain in the M3 state and shall be powered up when
the necessary power budget becomes available. If the FRU decides to operate at a lower power
level and notifies the Shelf Manager and the new power level is within the current Shelf Power
envelope, the CMM shall send the Set_Power_Level (new desired level) command to the FRU.
7.3 Graceful FRU Extraction
When the CMM receives a FRU Hot swap request for extraction, the CMM will send the deactivate
state command, and the FRU will transition to M6 state and begin its shut-down procedures. Once
the FRU has shut down, it transitions to M1 state, and the CMM then reclaims the FRU’s power
and adjusts the power budget for the newly available power.