mem: Add an API for requesting a back door without a Packet/Request.
Make this part of the Functional protocol, since it should always
return immediately, can be shared by the atomic and timing protocols,
and thematically fits with that protocol.
The default implementation on the receiving end just ignores the
request and leaves the back door pointer set to null, effectively
making back doors default "off" which matches their behavior in the
atomic protocol.
This mechamism helps fix a bug in the TLM gem5 bridges which need to
translate to/from the DMI and back door mechanisms, where there can be
an explicit request for a back door which does not have a transaction
associated with it. It is also necessary for bridging DMI requests in
timing mode, since the DMI requests must be instant, and the timing
protocol does not send/receive packets instantly.
Change-Id: I905f13b9bc83c3fa7877b05ce932e17c308125e2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65752
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Gabe Black <gabeblack@google.com>
4 files changed
