7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vladyslav Tymoshchuk [ Upstream commit 0ea3e0b196f9dcc17b40ac881a6efef06459975b ] q6apm_dai_pointer() turns the number of period buffers the DSP has returned in the current lap, 1..periods, into a position and reports one frame less than that. Commit a93dad6f4e6a ("ASoC: q6apm-dai: make use of q6apm_get_hw_pointer") added the "- 1" so that the end of the ring is not reported as a position equal to the buffer size. One frame short has a cost once the application stops feeding the stream. The DSP returns the last queued buffer and the position stops at appl_ptr - 1, so avail stays at buffer_size - 1, below the default stop_threshold. The DSP sends nothing more as its queue is empty, so no period interrupt comes either: ALSA never detects the underrun and the stream stays RUNNING. A poll-driven application that missed its last wakeup waits forever, and drain only ends on its timeout, with -EIO. On capture, the last frame of each period is held back until the next one. Before that commit the position wrapped to 0 at the end of the ring. Do that again. A full lap is the start of the ring, and snd_pcm_update_hw_ptr0() accounts for the wrap: the position cannot move by more than one lap between two updates, as each returned buffer calls snd_pcm_period_elapsed() and the DSP holds at most periods buffers. Seen on a OnePlus Pad 3 (SM8750) with PipeWire in interrupt-driven scheduling: after a stall the PCM sat at hw_ptr 78239, appl_ptr 78240 (avail 3839 of 3840) for two hours. Fixes: a93dad6f4e6a ("ASoC: q6apm-dai: make use of q6apm_get_hw_pointer") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Vladyslav Tymoshchuk Reviewed-by: Srinivas Kandagatla Tested-by: Srinivas Kandagatla Link: https://patch.msgid.link/20261014162703.10172-2-tvlad744@gmail.com Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- sound/soc/qcom/qdsp6/q6apm-dai.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/sound/soc/qcom/qdsp6/q6apm-dai.c b/sound/soc/qcom/qdsp6/q6apm-dai.c index 033197bdd8705..cac59c1015862 100644 --- a/sound/soc/qcom/qdsp6/q6apm-dai.c +++ b/sound/soc/qcom/qdsp6/q6apm-dai.c @@ -498,11 +498,15 @@ static snd_pcm_uframes_t q6apm_dai_pointer(struct snd_soc_component *component, ptr = bytes_to_frames(runtime, index); return ptr; } - ptr = q6apm_get_hw_pointer(prtd->graph, substream->stream) * runtime->period_size; - if (ptr) - return ptr - 1; + /* + * The hw pointer counts the period buffers the DSP has returned in + * this lap, 1..periods. A full lap is the start of the ring again: + * report 0 rather than one frame less, so that the position of a + * drained buffer reaches appl_ptr and ALSA sees the underrun. + */ + ptr = q6apm_get_hw_pointer(prtd->graph, substream->stream) % runtime->periods; - return 0; + return ptr * runtime->period_size; } static int q6apm_dai_hw_params(struct snd_soc_component *component, -- 2.53.0