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How to understand Device-nGRE?

ocean

Hi, experts,

Re-Orderingis a new attribute in ARMv8.

Can you explain Device-nGRE, and How to distinguish Device-nGRE and Device-nGnRE?

Thanks.

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    Hello,

    The three device attributes are G, R, and E, with the following definitions:

    • Gathering (G/nG)
      - Determines whether multiple accesses can be merged into a single bus transaction
      - nG: Number/size of accesses on the bus = number/size of accesses in code
    • Reordering (R/nR)
      - Determines whether accesses to the same device can be reordered
      - nR: Accesses to the same IMPLEMENTATION DEFINED block size will appear on the bus in program order
    • Early Write Acknowledgement (E/nE)
      - Indicates to the memory system whether a buffer can send acknowledgements
      - nE: The response should come from the end slave, not buffering in the interconnect

    So with the above said:

    • Device-nGRE is device memory where Reordering and Early Write Acknowledgements are allowed, but multiple accesses cannot be merged into a single bus transaction
    • Device-nGnRE is device memory where Early Write Acknowledgements are allowed, but multiple accesses cannot be merged into a single bus transaction, and accesses to the same IMPLEMENTATION DEFINED block size will appear on the bus in program order

    I hope that helps,

    Ash.

Reply
  • 0

    Hello,

    The three device attributes are G, R, and E, with the following definitions:

    • Gathering (G/nG)
      - Determines whether multiple accesses can be merged into a single bus transaction
      - nG: Number/size of accesses on the bus = number/size of accesses in code
    • Reordering (R/nR)
      - Determines whether accesses to the same device can be reordered
      - nR: Accesses to the same IMPLEMENTATION DEFINED block size will appear on the bus in program order
    • Early Write Acknowledgement (E/nE)
      - Indicates to the memory system whether a buffer can send acknowledgements
      - nE: The response should come from the end slave, not buffering in the interconnect

    So with the above said:

    • Device-nGRE is device memory where Reordering and Early Write Acknowledgements are allowed, but multiple accesses cannot be merged into a single bus transaction
    • Device-nGnRE is device memory where Early Write Acknowledgements are allowed, but multiple accesses cannot be merged into a single bus transaction, and accesses to the same IMPLEMENTATION DEFINED block size will appear on the bus in program order

    I hope that helps,

    Ash.

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