test: Drive OBI backend ports with native obi_sim_mem#140
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The OBI test path converted each backend OBI port to AXI via idma_obi2axi_bridge (per2axi), joined read+write with axi_rw_join, and shared one axi_sim_mem. The per2axi bridge wedges on rw-decoupled OBI transfers >512 B (stops accepting memory responses), hanging the vsim-sim-random OBI tests. The iDMA RTL is correct; the wedge is in the testbench bridge. Attach obi_sim_mem directly to the backend OBI ports (separate read/write mems, scoreboard seeds the read mem and checks the write mem), drop the per2axi bridges / axi_rw_join / AXI throttle+multicut for OBI, and repoint the OBI highlighters and watchdog to the native OBI handshakes. AXI path unchanged.
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Problem
The
vsim-sim-randomOBI tests (rw_obi,r_obi_w_axi,r_axi_w_obi,snitch_*) hang on rw-decoupled transfers ≳512 B. Root cause is in the testbench, not the iDMA RTL: the OBI path converts each backend OBI port to AXI via the vendoredper2axiperipheral converter, joins read+write withaxi_rw_join, and shares oneaxi_sim_mem. Under rw-decoupled burst traffic the per2axi bridge stops accepting memory responses (b_ready=0/r_ready=0while the memory holdsb_valid/r_valid), so nothing completes. The backend's native OBI write is independently proven deadlock-free against a responsive memory.Fix
Drive the backend's OBI ports with a native
obi_sim_mem(separate read/write memories; scoreboard seeds src in the read mem and checks dst in the write mem). Drop the per2axi bridges,axi_rw_join, and AXI throttle/multicut for OBI; repoint the OBI highlighters and watchdog to the native OBI handshakes. AXI path unchanged.Validation
Locally (Questa): rw_obi (incl. the previously-hanging seed), r_obi_w_axi, r_axi_w_obi, snitch variants, and rw_axi (AXI path) suites all green. This PR runs from an upstream branch so the GitLab sims execute in CI (fork PRs skip them).