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rebbarb/gc_bba_test/README.md
T
Roflin d8725392a5 gc_bba_test: fix inverted EXI error checks; builds clean
libogc's EXI functions return '1 on success, <=0 on error', but every call
site tested '== 0'.  A -1 error return therefore read as success, so a failed
EXI_Lock or EXI_Select would fall through and the subsequent transfer would
produce garbage reported as a misleading test failure rather than an EXI
error.  All six call sites now test <= 0.

Also retries EXI_Lock for ~100 ms: it fails outright rather than blocking when
another subsystem holds the channel, and Swiss or a libogc driver may hold it
briefly -- without the retry a transient collision surfaces as a test failure.

Builds clean with devkitPPC 16.1.0 / GCC 16, no warnings: 172 KB .dol.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-10-03 11:24:47 +02:00

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# re-bba-rb — on-console test suite (GameCube)
A `.dol` you run from Swiss that drives the adapter in Serial Port 1 and
reports pass/fail per test on the TV.
## Build
Needs devkitPro's `gamecube-dev` group (devkitPPC + libogc). The devcontainer
installs it — if `DEVKITPPC` is unset, **rebuild the container**, since the
toolchain is added in `.devcontainer/Dockerfile`.
```bash
make # -> gc_bba_test.dol
```
Copy the `.dol` to your SD card (SD Gecko / SD2SP2) and launch it from Swiss.
## Controls
| Button | |
|---|---|
| D-pad up/down | move |
| A | open a suite / rerun the selected test |
| X | run the selected suite |
| START | run everything |
| Y | clear all results |
| B | back |
## What it tests
| Suite | Proves |
|---|---|
| Identity | device enumerates: `04 02 02 00`, HIPR, NWAYS |
| Registers | PAR0–5, IMR writable and read back; IR is write-1-clear |
| Reset/control | NCRA RESET self-clears, SR holds |
| EXI integrity | 200 reads with no bit errors; which EXI clock indices work |
| Ethernet | MAC readback, 60-byte ARP transmit (TI), frame receive (RWP/RI) |
| SPRAM/DMA | ring descriptor is well-formed; reads ≥ 0x100 stream until CS |
## Things that will bite you
**The device ID is a ONE-SHOT.** Address 0 returns `04 02 02 00` only until
the first NCRA reset clears `id_phase` in the gateware; after that it reads
back NCRA. That is correct — it matches the GC's own init order — but it means
the Identity test can only pass once per *console power cycle*. Run it before
the Reset suite. On a re-run the app reports SKIP with an explanation rather
than a misleading failure.
**TI is not proof of transmission.** It only means `TXFrameDrain` handed the
frame to the W5100. A frame can set TI and never reach the wire. The TX test
says so; to confirm the wire, capture on a PC or watch the RX test pick up a
reply.
**The RX test needs traffic.** It waits ~2 s for any frame. On an isolated
link with nothing talking it will fail legitimately — give the PC an address on
the same subnet (the ARP the TX test sends is aimed at `10.0.0.50`, so
`sudo ip addr add 10.0.0.50/24 dev <nic>` makes the PC answer it and both tests
pass together).
**Never over-clock a register read.** Asking for N bytes and clocking more
leaves stale prefetched bytes queued and desynchronises the *next* transaction
— a deterministic every-Nth-read corruption that looks like a signal-integrity
fault. `bba_read()` clocks exactly `len`; don't "round up" for convenience.
**TXDATA takes one byte per transaction.** The register file's effective
address auto-increments per data byte, so a 4-byte write to 0x48 would spill
into 0x49–0x4B. `bba_tx_bytes()` does it correctly.
## Build status
Builds clean (no warnings) with devkitPPC 16.1.0 / GCC 16 in the devcontainer:
`gc_bba_test.dol`, ~172 KB, entry `0x80003100`.
`.gitignore` excludes the build products — run `make` to produce the `.dol`.