changeset 2a5b4e334f7d in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=2a5b4e334f7d
description:
misc: Clean up and complete the gem5<->SystemC-TLM bridge [9/10]
The current TLM bridge only provides a Slave Port that allows the gem5
world to send request to the SystemC world. This patch series refractors
and cleans up the existing code, and adds a Master Port that allows the
SystemC world to send requests to the gem5 world.
This patch:
* Pay for the header delay that the gem5 XBar annotates to packets.
Reviewed at http://reviews.gem5.org/r/3798/
Signed-off-by: Jason Lowe-Power <[email protected]>
diffstat:
util/tlm/sc_master_port.cc | 12 +++++++++---
util/tlm/sc_slave_port.cc | 27 ++++++++++++++++++++++++++-
2 files changed, 35 insertions(+), 4 deletions(-)
diffs (61 lines):
diff -r 9487cdff1bc3 -r 2a5b4e334f7d util/tlm/sc_master_port.cc
--- a/util/tlm/sc_master_port.cc Thu Feb 09 19:15:46 2017 -0500
+++ b/util/tlm/sc_master_port.cc Thu Feb 09 19:15:48 2017 -0500
@@ -329,9 +329,15 @@
sc_assert(pkt->isResponse());
- // pay for annotaded transport delays
- auto delay =
- sc_core::sc_time::from_value(pkt->payloadDelay + pkt->headerDelay);
+ /*
+ * Pay for annotated transport delays.
+ *
+ * See recvTimingReq in sc_slave_port.cc for a detailed description.
+ */
+ auto delay = sc_core::sc_time::from_value(pkt->payloadDelay);
+ // reset the delays
+ pkt->payloadDelay = 0;
+ pkt->headerDelay = 0;
auto tlmSenderState = dynamic_cast<TlmSenderState*>(pkt->popSenderState());
sc_assert(tlmSenderState != nullptr);
diff -r 9487cdff1bc3 -r 2a5b4e334f7d util/tlm/sc_slave_port.cc
--- a/util/tlm/sc_slave_port.cc Thu Feb 09 19:15:46 2017 -0500
+++ b/util/tlm/sc_slave_port.cc Thu Feb 09 19:15:48 2017 -0500
@@ -214,9 +214,34 @@
Gem5Extension* extension = new Gem5Extension(packet);
trans->set_auto_extension(extension);
+ /*
+ * Pay for annotated transport delays.
+ *
+ * The header delay marks the point in time, when the packet first is seen
+ * by the transactor. This is the point int time, when the transactor needs
+ * to send the BEGIN_REQ to the SystemC world.
+ *
+ * NOTE: We drop the payload delay here. Normally, the receiver would be
+ * responsible for handling the payload delay. In this case, however,
+ * the receiver is a SystemC module and has no notion of the gem5
+ * transport protocol and we cannot simply forward the
+ * payload delay to the receiving module. Instead, we expect the
+ * receiving SystemC module to model the payload delay by deferring
+ * the END_REQ. This could lead to incorrect delays, if the XBar
+ * payload delay is longer than the time the receiver needs to accept
+ * the request (time between BEGIN_REQ and END_REQ).
+ *
+ * TODO: We could detect the case described above by remembering the
+ * payload delay and comparing it to the time between BEGIN_REQ and
+ * END_REQ. Then, a warning should be printed.
+ */
+ auto delay = sc_core::sc_time::from_value(packet->payloadDelay);
+ // reset the delays
+ packet->payloadDelay = 0;
+ packet->headerDelay = 0;
+
/* Starting TLM non-blocking sequence (AT) Refer to IEEE1666-2011 SystemC
* Standard Page 507 for a visualisation of the procedure */
- sc_core::sc_time delay = sc_core::SC_ZERO_TIME;
tlm::tlm_phase phase = tlm::BEGIN_REQ;
tlm::tlm_sync_enum status;
status = transactor->socket->nb_transport_fw(*trans, phase, delay);
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