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fix: keep Joy-Con links fast and stop idle rumble writes

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Joey Yakimowich-Payne 2026-09-07 20:35:02 -06:00
commit 79a72d811d
10 changed files with 220 additions and 84 deletions
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ADAPTER_PARITY_PLAN.md
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@ -819,26 +819,40 @@ from 197 host requests without queue drops; the user confirmed both sides.
Normal GATT-client busy responses now retain queued output instead of
disconnecting the controller.
Two or more Switch 2 BLE links now select 30 ms connection intervals even
before Classic connects; a single Switch 2 link retains 7.5 ms. Paired and
Individual Joy-Cons use the same physical-link policy. This trades Switch 2
delivery latency for Classic paging and streaming airtime without changing
HD encoding or bonds. The earlier policy waited for a Classic link and passed
one physical power-off/reconnect check, but subsequent use exposed intermittent
DualSense connection failures with two Joy-Cons already active. Regression
coverage now requires airtime before Classic admission and after its departure.
The user confirmed reconnects and actuator output/clean stops at 30 ms.
A same-workload 15/30 ms comparison at 300 MHz rejected 15 ms for native
haptics: it timed out around four seconds, with 111 PCM sends, 38 skips and
one send failure. At 30 ms the full 30-second run retained all three links
and native streaming: 1,384 PCM sends, 47 skips, no send failures or host-update/
Switch 2 ingress drops, and seven Joy-Con output-stage drops. The isolated
DualSense fixture delivered all 288 packets without skips. Release images keep
30 ms; long-duration reliability remains unqualified. All 349 tests and four
affected firmware builds passed for the preconnection policy.
A prior 30-second production mixed-rumble run kept native DualSense streaming,
with no send failures or ingress drops, 14 Joy-Con output-stage discards and
nine PCM skips. It is not lossless.
Joy-Con 2 links now retain 7.5 ms BLE intervals in Paired and Individual modes,
including when a Classic controller connects. This intentionally removes their
automatic 30 ms slowdown while preserving the idle-neutral sending fix. Other
Switch 2 models retain 30 ms when multiple physical Switch 2 links are present,
otherwise 7.5 ms; unrelated BLE controllers are untouched. Lifecycle coverage
checks modes, Classic arrival/departure, handle reuse, slow-interval correction,
and the remaining Switch 2 Pro coexistence/retry policy.
Idle-neutral output ends after three successful neutral submissions/completions.
Late non-neutral completion re-arms stops even after a logical reset; failed or
pending writes do not consume the budget. Native subframes, expiry and normal
active-output cadence remain unchanged. The direct lab fixtures and unqualified
shared Classic/GATT admission experiment are excluded from this checkpoint.
Measured limits remain important:
- At 30 ms, idle suppression reduced outgoing HCI ACL writes from 974 to 469 per
ten seconds with the same 469 DualSense PCM sends. Total HCI transactions did
not decrease because receive-credit traffic increased.
- The optimized 30-second mixed run sent 1,431 PCM packets without skips/send
failures, but had two Switch 2 ingress drops and nine output-stage drops.
The user later clarified that 30 ms Joy-Con rumble was weak; activity and
clean stops were not full quality approval. DualSense was weak/inconsistent.
- A single right-Joy-Con direct-packet reference confirmed clear tone and good
feel at a nominal 7.5 ms packet cadence: 267 packets per two-second burst,
7.504 ms average submission spacing, same 320 Hz/amplitude as the weak 20 ms
one-/three-sample trials. This is distinct from the BLE link interval.
- Adding DualSense PCM to the fast fixture timed out in about 0.66 seconds,
with one or both Joy-Cons vibrating (both links connected in either case).
Both runs sent only 11 PCM packets; the two-vibrating run also had Joy-Con
submission gaps up to 32 ms. Explicit stop writes completed after abort.
The requested fast-link default is not a claim of reliable mixed native PCM,
lossless transport or qualified endurance. DualSense buffer/cadence work remains
separate; no hidden gain or compatibility fallback change is included.
The native-HD checkpoint passed 289 tests and all five firmware builds; its
40 pre-existing profiles and metadata survived. Its inventory then contained