apple-bce: fix scheduling while atomic and playback timestamp#50
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Vakarux12 wants to merge 2 commits into
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apple-bce: fix scheduling while atomic and playback timestamp#50Vakarux12 wants to merge 2 commits into
Vakarux12 wants to merge 2 commits into
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Two fixes to the bundled apple-bce driver, syncing with upstream t2linux/apple-bce-drv: 1. audio/pcm: skip period_elapsed for streams that are not started The T2 chip sends timestamp events for all devices continuously. Calling snd_pcm_period_elapsed() on a stopped stream causes the ALSA state machine to call aaudio_pcm_trigger(STOP), which blocks on wait_for_completion_timeout(). On PREEMPT(full) kernels the BCE DMA IRQ handler runs with BHs disabled, so this triggers: BUG: scheduling while atomic Fix: return early when stream->started == 0. 2. audio/pcm: use os_timestamp for PLAYBACK in aaudio_handle_timestamp PLAYBACK was using dev_timestamp (T2 clock domain) while CAPTURE correctly used os_timestamp. After module re-probe the T2 clock can drift, causing wild PCM positions and XRUNs. Use os_timestamp for both streams.
aaudio_cmd_stop_io blocks waiting for a T2 reply. When called from PCM trigger(STOP) it can block PipeWire's main thread while the RT data thread holds a PI mutex the main thread needs, causing a deadlock. It can also be called from atomic context (BCE DMA BH handler) causing scheduling-while-atomic. Always defer via schedule_work. In trigger(START) use cancel_work_sync to cancel any pending stop before starting without blocking callers.
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Syncs the bundled apple-bce driver with fixes from t2linux/apple-bce-drv#31.
Fix 1: skip period_elapsed for streams that are not started
Symptom: Connecting speakers or headphones to the 3.5mm jack causes
BUG: scheduling while atomicinirq/bce_dma, followed by a flood ofaaudio_pcm_pointer while not startedmessages. System becomes unresponsive for audio.Cause: The T2 chip sends timestamp events for all registered audio devices continuously, even when no ALSA stream is open.
aaudio_handle_stream_timestamp()was unconditionally callingsnd_pcm_period_elapsed(), which on a stopped stream chains intosnd_pcm_do_stop→aaudio_pcm_trigger(STOP)→wait_for_completion_timeout(). The BCE DMA IRQ handler runs with BHs disabled, so any attempt to sleep triggers the bug.Fix: Return early when
stream->started == 0, matching the guard already inaaudio_pcm_pointer().Fix 2: use os_timestamp for PLAYBACK
Cause:
aaudio_handle_timestamp()was passingdev_timestamp(T2 clock domain) to the PLAYBACK substream while CAPTURE correctly usedos_timestamp. After suspend/resume or module re-probe the T2 clock drifts, causing wild PCM positions and XRUNs.Fix: Use
os_timestampfor both PLAYBACK and CAPTURE.Tested
MacBookPro16,1, kernel 7.0.12-arch1-Watanare-T2-1-t2, PREEMPT(full). Before: connecting speakers crashed audio. After: clean kernel log, audio works on both speakers and headphones.