PPA sweep on NVDLA partition_c (asap7)

[mguthaus]

Background

partition_c is the densest NVDLA partition — 84 FakeRAM macro instances packed into an asap7 die. It landed in #68 at CORE_UTILIZATION=40 / PLACE_DENSITY_LB_ADDON=0.30 / MACRO_PLACE_HALO=3 3, with a 42% final utilization, which is the lowest of the 5 partitions.

The tuning journey that got us there was about trading utilization for flow completion, not finding a PPA optimum:

#	util / addon / halo	Furthest stage	Failure
1	50 / 0.25 / 2	post-CTS DPL	DPL-0036: clkbuf couldn't legalize near cbuf_ram_bank31
2	45 / 0.30 / 5	MPL floorplan	MPL-0003: no valid tilings (halo×84 ate tiling budget)
3	48 / 0.25 / 3	GRT	GRT-0116: placed but routed-congested
4	40 / 0.30 / 3	6_final	Succeeded (42% util)

Task

Run a proper PPA sweep on partition_c to reclaim utilization without regressing any flow stage. Suggested grid:

• MACRO_PLACE_HALO ∈ {3, 4}
• CORE_UTILIZATION ∈ {40, 42, 44, 46}
• PLACE_DENSITY_LB_ADDON ∈ {0.25, 0.28, 0.30}

Acceptance

• Clean bazel build //designs/asap7/NVDLA/partition_c:partition_c_final end-to-end (no DPL-0036, MPL-0003, or GRT-0116).
• Final utilization > 42% (stretch: 48–50%).
• No timing / power regression vs. the current configuration.

Related

• PR Add NVDLA nv_small partitions (a/c/m/o/p) on asap7 #68 (NVDLA port, current partition_c config)
• optimize-ppa skill is a good starting point for the sweep harness.