croc

PULP's Croc, a small SoC around the CVE2 core with OBI inside, taped out in IHP 130 nm, taken as a black box.

Part of the Tape-Out IP library, wired up by xirang. One submodule, not modified: third_party/croc. Its own submodules (the two IHP PDKs and artistic) are not fetched.

What this repository adds

Upstream vendors every dependency into rtl/ and lists the sources with bender. The flist setup task runs bender with the targets upstream's verilator/run_verilator.sh uses and writes two file lists under build/flist/: rtl.f for the SoC and sim.f with upstream's testbench added.

The configuration lives in croc_pkg.sv as localparams, out of -D's and -G's reach. The setup task copies that file and makes iDMAEnable and CorePMPEnable read a macro whose default is upstream's value; the idma and pmp knobs set the macros. The receipt reads both localparams back after elaboration at every point.

The top is croc_soc: the core, SRAM, peripherals and the debug module, without the pads of croc_chip. Its ports are JTAG, UART, GPIO, a second clock for the CLINT, the test mode input and a status output.

$ ran run croc flist
$ ran test croc

Testing

The sim task follows upstream's .github/scripts/run_sim_flow.sh at every point: it builds the software in sw/ with riscv64-unknown-elf-gcc and upstream's testbench with Verilator, then runs

• helloworld, checking the UART greeting;
• print_config, which prints the SoC's hardware info register. The expected lines are computed from the point's knobs, so a knob that does not reach the RTL fails here;
• every unit test in sw/test/, each of which must end with Simulation finished: SUCCESS. test_idma runs only where the iDMA is on.

Limits

The SRAM stays at two banks of 512 words, as the address map in croc_pkg.sv is written for that; changing the banks or their depth means changing the map too. The SRAM is the behavioural model from tech_cells_generic, not upstream's IHP macros. The user domain is empty, and its OBI ports are inside croc_soc. The CLINT's reference clock is listed with the other pins, as a package declares one clock for now.

License

This repository: 任选其一 MIT · Apache 2.0 · 木兰宽松许可证 第2版.

third_party/croc stays under SHL-0.51 (Solderpad Hardware License), which lets a licensee take it under Apache-2.0 instead; see its LICENSE.md.