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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.

Parents
  • 0 in reply to Ash Wilding

    Hi Ash,

    in the case of Device-nGnRE, what does IMPLEMENTATION DEFINED block size means?

    Is it related to (according to the Armv8 architecture specification)

    A Memory-mapped peripheral occupies a memory region of IMPLEMENTATION DEFINED size and
    can be accessed using load and store instructions.

     

    My misunderstanding comes from the Armv7a specification which states:

     

    in A3.8.2 Ordering requirements for memory accesses:

    The size of a memory mapped peripheral, or a block of memory, is IMPLEMENTATION DEFINED, but is not smaller
    than 1KByte.

    Note: This implies that the maximum memory-mapped peripheral size for which the architecture guarantees order for all
    implementations is 1KB.

     

    If the pheriperal has a memory map greater than 1KB, the Armv7 architecture doesn't guarantee ordering? If true, does the same limitation

    exist for Armv8, for the Device-nGnRE? 

     

    Bas

     

     

     

     

     

     

     

Reply
  • 0 in reply to Ash Wilding

    Hi Ash,

    in the case of Device-nGnRE, what does IMPLEMENTATION DEFINED block size means?

    Is it related to (according to the Armv8 architecture specification)

    A Memory-mapped peripheral occupies a memory region of IMPLEMENTATION DEFINED size and
    can be accessed using load and store instructions.

     

    My misunderstanding comes from the Armv7a specification which states:

     

    in A3.8.2 Ordering requirements for memory accesses:

    The size of a memory mapped peripheral, or a block of memory, is IMPLEMENTATION DEFINED, but is not smaller
    than 1KByte.

    Note: This implies that the maximum memory-mapped peripheral size for which the architecture guarantees order for all
    implementations is 1KB.

     

    If the pheriperal has a memory map greater than 1KB, the Armv7 architecture doesn't guarantee ordering? If true, does the same limitation

    exist for Armv8, for the Device-nGnRE? 

     

    Bas

     

     

     

     

     

     

     

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