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ACE protocol : Eviction and snoop request at same time

How to handle below scenario ?

  • At time t1 let us suppose L1 data cache is evicting a line and write address is sent on write address channel by asserting AWVALID (AWREADY is high)
  • At same time t1, there is a snoop request from interconnect on snoop address channel with ACVALID signal asserted but ACREADY signal is low.
  • Both write address and snoop address are same, let us say address is ‘X’.
    • From Data cache point of view eviction address is accepted by the interconnect and eviction is in progress (write address channel)
    • From Interconnect point of view snoop request is issued on the channel and request will not be modified until there is ready signal from Data cache (snoop address channel)
    • In this case when snoop request is accepted by the Data cache, snoop address ‘X’ will not be present in Data cache.

Consider interconnect has snoop filter. As per the snoop filter the snoop request should be hit in cache but it will be a miss in this case.

Questions :

  1. Since data cache evicted the line, should it give snoop response indicating that line is not present in cache ?