Interconnect backward transactions

[SumitK]

Hi Folks

In my inteconnect model, I have a target socket In (which allows multiple initiator sockets connected to it) and an array of initiator socket like folloiwng

tlm_utils::multi_passthrough_target_socket<QC_Mux_base<N_TARGETS>, 32, tlm::tlm_base_protocol_types,0,sc_core::SC_ZERO_OR_MORE_BOUND >  In

tlm_utils::multi_passthrough_initiator_socket<QC_Mux_base<N_TARGETS>, 32, tlm::tlm_base_protocol_types,1,sc_core::SC_ZERO_OR_MORE_BOUND > Out[MAX]

Now if I receive some backward transaction, e.g. nb_transport_bw or invalidate_direct_mem_ptr, on some of the Out socket, I need to forward it via In socket. 

For that do I just say

In->nb_transport_bw(...) and

In->invalidate_direct_mem_ptr(...)

or

for(unsigned int i=0; i< In.size(); i++)

In->nb_transport_bw(...)

and

for(unsigned int i=0; i< In.size(); i++)

In->invalidate_direct_mem_ptr(...)

wrt compilation, both are accepted

Thanks in Advance

Thanks

Sumit

[Eyck]

Hi Sumit,

both options will forward your transaction only to the first bound initiator socket of your multi_passthrough_target_socket as it just calls the operator->() of the underlying port.

What you want to do is:

for(unsigned int i=0; i<In.size(); ++i)
	In[i]->invalidate_direct_mem_ptr(...)

But here you forward the call to all initiator sockets. In case of invalidate_direct_mem_ptr() this might be ok but for nb_transport_bw() it isn't as the call is part of the AT phases protocol and then you send e.g a BEG_RESP to a socket which never sent a BEG_REQ thus violating the TLM protocol as specified in the TLM 2.0 LRM (e.g. section 8.2.6)

Cheers

-Eyck

[SumitK]

On 3/22/2018 at 10:43 AM, Eyck said:

Hi Sumit,

both options will forward your transaction only to the first bound initiator socket of your multi_passthrough_target_socket as it just calls the operator->() of the underlying port.

What you want to do is:

for(unsigned int i=0; i<In.size(); ++i)
	In[i]->invalidate_direct_mem_ptr(...)

But here you forward the call to all initiator sockets. In case of invalidate_direct_mem_ptr() this might be ok but for nb_transport_bw() it isn't as the call is part of the AT phases protocol and then you send e.g a BEG_RESP to a socket which never sent a BEG_REQ thus violating the TLM protocol as specified in the TLM 2.0 LRM (e.g. section 8.2.6)

Cheers

-Eyck

Hi Eyck

My mistake, I mean to say

for(unsigned int i=0; i<In.size(); ++i)

        In[i]->invalidate_direct_mem_ptr(...)

In my platform, when I just call In->invalidate_direct_mem_ptr(...), I see it reaches to all connected sockets . but you said it will reach only to first bound initiator socket.  I am confused here.

What is different between

In->invalidate_direct_mem_ptr(...)

and 

for(unsigned int i=0; i<In.size(); ++i)

    In[i]->invalidate_direct_mem_ptr(...)

With both the cases, how we should handle nb_transport_bw()  so that it reaches only to intended recipients ?

Thanks

Sumit

[SumitK]

Hi Eyck

Please ignore my last thread. It was my mistake.

I should use

for(unsigned int i=0; i<In.size(); ++i)

    In[i]->invalidate_direct_mem_ptr(...)

and 

 

for(unsigned int i=0; i<In.size(); ++i)

    In[i]->nb_transport_bw() // only is corresponding nb_transport_fw() is received on that In

My only remaining point is now wrt nb_transport_bw() calls. For this if I want to make sure that my interconnect model only pass that calls to that initiator socket from which the corresponding nb_transport_fw() call is received, do I need to add the corresponding checks in interconnect model itself before forwarding the transaction using  nb_transport_bw() call ?

Thanks

Sumit