hardware_pio: fix pio_encode_mov(pio_pindirs, ...) on RP2350 #2946

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anoshyn wants to merge 1 commit from fix-pio-mov-pindirs into develop

anoshyn commented

2026-05-16 06:16:16 -05:00

(Migrated from github.com)

Summary

Fixes #2754. On RP2350, pio_encode_mov(pio_pindirs, pio_x) returned 0xA081 (which is MOV EXEC, X) instead of the correct 0xA061 (MOV PINDIRS, X).

The PIO MOV destination encoding for PINDIRS differs from the SET/IN/OUT encoding:

SET/IN/OUT encode PINDIRS as field 4
MOV (RP2350 only) encodes PINDIRS as field 3; field 4 is reserved for EXEC

The pio_src_dest enum collapses both pio_pindirs and pio_exec_mov to low-3-bits = 4 because the SET/IN/OUT encoder is the original consumer. The MOV encoder needs to remap PINDIRS to 3 — but only for PINDIRS, not for EXEC. In release builds (NDEBUG), pio_pindirs and pio_exec_mov are numerically identical (the _PIO_INVALID_* flag bits are all zero), so a naive "dest == 4 → 3" remap would also break pio_encode_mov(pio_exec_mov, ...).

This PR adds a non-NDEBUG-gated marker bit (_PIO_MARKER_PINDIRS = 0x100) carried only by pio_pindirs. The new _pio_mov_dest_bits() helper checks the marker on PICO_PIO_VERSION > 0 and remaps to 3. All existing encoders already mask with & 7u before emitting the destination field, so the marker bit is discarded everywhere it isn't being checked — no other encoder is affected. The debug-mode _PIO_INVALID_MOV_DEST assertion is also dropped from pio_pindirs on RP2350.

Test plan

Host-side verification of the constant-folded encoding emitted by each pio_encode_*:

test	RP2350 (v1)	RP2040 (v0)
`mov pindirs, x`	0xA061 (fixed)	0xA081 (unchanged; invalid on RP2040)
`mov exec_mov, x`	0xA081 ✓	0xA081 ✓
`mov pc, x`	0xA0A1 ✓	0xA0A1 ✓
`mov y, y` (NOP)	0xA042 ✓	0xA042 ✓
`set pindirs, 1`	0xE081 ✓	0xE081 ✓
`out pindirs, 1`	0x6081 ✓	0x6081 ✓
`in pins, 1`	0x4001 ✓	0x4001 ✓
`mov_not pindirs, x`	0xA069 ✓	0xA089 ✓
`mov_reverse pindirs, x`	0xA071 ✓	0xA091 ✓

Full SDK build clean for PICO_PLATFORM=rp2040 PICO_BOARD=pico.
Full SDK build clean for PICO_PLATFORM=rp2350 PICO_BOARD=pico2.
CI to confirm broader configurations (RISC-V, alternate boards).

## Summary Fixes #2754. On RP2350, `pio_encode_mov(pio_pindirs, pio_x)` returned `0xA081` (which is `MOV EXEC, X`) instead of the correct `0xA061` (`MOV PINDIRS, X`). The PIO MOV destination encoding for PINDIRS differs from the SET/IN/OUT encoding: - SET/IN/OUT encode PINDIRS as field **4** - MOV (RP2350 only) encodes PINDIRS as field **3**; field 4 is reserved for EXEC The `pio_src_dest` enum collapses both `pio_pindirs` and `pio_exec_mov` to low-3-bits = 4 because the SET/IN/OUT encoder is the original consumer. The MOV encoder needs to remap PINDIRS to 3 — but only for PINDIRS, not for EXEC. In release builds (`NDEBUG`), `pio_pindirs` and `pio_exec_mov` are numerically identical (the `_PIO_INVALID_*` flag bits are all zero), so a naive "dest == 4 → 3" remap would also break `pio_encode_mov(pio_exec_mov, ...)`. This PR adds a non-`NDEBUG`-gated marker bit (`_PIO_MARKER_PINDIRS = 0x100`) carried only by `pio_pindirs`. The new `_pio_mov_dest_bits()` helper checks the marker on `PICO_PIO_VERSION > 0` and remaps to 3. All existing encoders already mask with `& 7u` before emitting the destination field, so the marker bit is discarded everywhere it isn't being checked — no other encoder is affected. The debug-mode `_PIO_INVALID_MOV_DEST` assertion is also dropped from `pio_pindirs` on RP2350. ## Test plan Host-side verification of the constant-folded encoding emitted by each `pio_encode_*`: | test | RP2350 (v1) | RP2040 (v0) | |---|---|---| | `mov pindirs, x` | **0xA061** (fixed) | 0xA081 (unchanged; invalid on RP2040) | | `mov exec_mov, x` | 0xA081 ✓ | 0xA081 ✓ | | `mov pc, x` | 0xA0A1 ✓ | 0xA0A1 ✓ | | `mov y, y` (NOP) | 0xA042 ✓ | 0xA042 ✓ | | `set pindirs, 1` | 0xE081 ✓ | 0xE081 ✓ | | `out pindirs, 1` | 0x6081 ✓ | 0x6081 ✓ | | `in pins, 1` | 0x4001 ✓ | 0x4001 ✓ | | `mov_not pindirs, x` | 0xA069 ✓ | 0xA089 ✓ | | `mov_reverse pindirs, x` | 0xA071 ✓ | 0xA091 ✓ | - [x] Full SDK build clean for `PICO_PLATFORM=rp2040 PICO_BOARD=pico`. - [x] Full SDK build clean for `PICO_PLATFORM=rp2350 PICO_BOARD=pico2`. - [ ] CI to confirm broader configurations (RISC-V, alternate boards).

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hardware_pio: fix pio_encode_mov(pio_pindirs, ...) on RP2350 #2946

Summary

Test plan

Pull request closed