apply for a new repo "openbmc/node-data-sync"

[Brad Bishop]

Hi Daniel

Typically email attachments are not opened.  To ensure your mail gets 
read, avoid attachments.  Resending without the attachment...

On Mon, Apr 19, 2021 at 12:41:00PM +0800, yugang.chen wrote:
>attach the design document, please take a look.
>
>Best Regards
>Daniel(Yugang)
>

># Modular System Support - PCH IO Expander
>
>Author: Chen, Yugang
>
>## Problem Description
>When multi modular 2 socket reference platforms (RP) are connected together,
>the BMCs on each RP shall support the ability to manage the system as either
>single 4S/8S system or standalone as 2S systems.
>
>## Background and References
>In 4S/8S mode, only one PCH works at DMI (Direct Media Interface) mode,
>this PCH is called legacy PCH (PCH.L), the other PCHs are called PCH IO Expander
>(PCH.IO). The BMC attached to the PCH.L works as a primary and the other BMCs
>work as secondaries.
>
>## Requirements
>Check a modular system as either 4S/8S or standalone mode by GPIOs on BMC each
>time system AC on.
>Each BMC works independently in standalone mode.
>In 4S/8S mode, only primary BMC is responsible for management of system level
>resources, secondary BMCs need to collect its local management resources and report
>them to primary BMC.
>
>## Proposed Design
>Each BMC will have a property to reveal its work mode. Users can know if BMC is in standalone mode or 4S/8S mode.
>Each BMC has another property to show if the BMC mode is PCH Legacy BMC or
>Non-Legacy BMC. PCH Legacy BMC is working as primary and Non-Legacy BMC working
>as secondary.
>
>Each time a BMC reboot, The BMC needs to check 3 GPIO Pins: FM_STANDALONE_MONDE_N / FM_4S_8S_N_MODE / FM_NODE_ID to get working mode as standalone mode or primary /secondary(4S/8S) role according to the GPIO values.
>After confirming the mode and BMCs' role, BMCs should set properties according
>to the correct configuration.
>In 4S/8S mode only node id 0 will be primary BMC because only this node will be the PCH.L. Node id 1,2,3 will be the secondary nodes.
>
>Once a BMC gets mode is in 4S/8S, node roles are configured by node
>ID (GPIO Pins) and keep consistent once AC on. Once node role check is done,
>
>In 4S/8S mode, Primary BMC needs to broadcast its role to make sure there is only
>one primary BMC in the system.
>
>Need a new feature to make sure secondary BMCs send local redfish events to primary
>BMC. And primary BMC needs to add a tag to those events coming from secondary BMC so
>that user can know the event logs happened on which node.
>
>Even in 4S/8S mode, each BMC will collect its local management resources,
>including sensors, fans and do FSC according to the values of local sensors.
>PSU and Fans on each node will not be connected together. Configuration
>settings of each secondary node will remain the same, and won't be synced across
>the nodes.
>
>In 4S/8S mode, PECI will only be connected to primary node. Primary BMC needs to
>monitor all CPU and DIMM sensors and deliver the sensor values of the CPUs/DIMMs
>on secondary nodes to secondary BMCs. So that secondary BMCs can use the sensor values to control their own FSCs. Primary BMC also needs to have a way to find how many
>CPUs are in the whole system include Primary and Secondary nodes.
>
>## Alternatives Considered
>Primary node monitors all the IPMI sensors in secondary nodes and creates redfish log
>by itself.
>
>Instead of BMC reboot, only AC cycle will make BMCs check GPIO pins and set
>Legacy BMC or Non-Legacy BMC mode.
>
>Only primary BMC broadcast its role and secondary only waiting for the broadcast
>from primary.
>
>## Impacts
>Only on the motherboard where legacy PCH is located, POST code/Front Panel/KCS
>port/UART will work, while these interfaces on board with non-legacy PCH will
>not work due to BIOS and HW design. And this will cause non-functioning of
>SOL/KVM/Virtual media on secondary BMCs.