frontend: Drop the unreachable INIT write path from inst64 - #218
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frontend: Drop the unreachable INIT write path from inst64#218DanielKellerM wants to merge 2 commits into
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inst64 instantiated idma_backend_rw_axi_rw_init_rw_obi, which carries an INIT write manager the frontend can never reach. DMINIT selects INIT as a source only, the module exposes no INIT ports, and dst_protocol is always AXI or OBI, so init_write_rsp was read by the backend and driven by nothing. Add r_init_rw_axi_rw_obi and instantiate that instead. This drops the dead write manager from the RTL rather than tying its response off, and clears the Spyglass W123 errors and W287a warnings reported in pulp-platform#172.
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The deploy workflow passes IDMA_BACKEND_IDS on the make command line, so its input default overrides idma.mk. Without the new id the deployed RTL would omit idma_backend_r_init_rw_axi_rw_obi, which inst64 now needs.
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Closes #172.
idma_inst64_topinstantiatedidma_backend_rw_axi_rw_init_rw_obi, a variant that carries an INITwrite manager the frontend can never reach:
DMINITsetssrc_protocol = INITonly, withsrc_addrcarrying the fill pattern; INIT is theconstant generator feeding a memset
dst_protocolis only ever AXI or OBISo
init_write_rspwas read by the backend and driven by nothing. Spyglass reported it as threeW123(severity Error underrtl_handoff) plus threeW287a, and sixW528on the mirror signalinit_write_req.Rather than tie the response off, this adds
r_init_rw_axi_rw_obiand instantiates that. Thegenerated variant has only
init_read_req_o/init_read_rsp_iand does not instantiateidma_init_write, so the dead manager leaves the RTL instead of relying on synthesis to prune it.Verification
lint_rtlon the inst64 frontendinit_write_req6 -> 0, 0 Errorstb_idma_inst64_axi_copy(Questa 2023.4)DMATracing=1tb_idma_backend_r_init_rw_axi_rw_obi, all 10 job filesmake idma_verify_backend IDMA_VERIFY_ID=r_init_rw_axi_rw_obimake idma_verify_sharedmake idma_verify_codegenTracing now matches the backend instance, so the stale caveat in
idma_inst64_tb_pkgis dropped.Downstream: snitch_cluster#330 waives
W123/W287awith the note "to fix inidma"; that waivercan be removed once this lands and the iDMA pin moves.