6.6-stable review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
[ Upstream commit 4f9d674377d090e38d93360bd4df21b67534d622 ]
The low-latency mode of USB-audio driver uses a similar approach like the implicit feedback mode but it has an explicit queuing at the trigger start time. The difference is, however, that no packet will be handled any longer after all queued packets are handled but no enough data is fed. In the case of implicit feedback mode, the capture-side packet handling triggers the re-queuing, and this checks the XRUN. OTOH, in the low-latency mode, it just stops without XRUN notification unless any new action is taken from user-space via ack callback. For example, when you stop the stream in aplay, no XRUN is reported.
This patch adds the XRUN check at the packet complete callback in the case all pending URBs are exhausted. Strictly speaking, this state doesn't match really with XRUN; in theory the application may queue immediately after this happens. But such behavior is only for 1-period configuration, which the USB-audio driver doesn't support. So we may conclude that this situation leads certainly to XRUN.
A caveat is that the XRUN should be triggered only for the PCM RUNNING state, and not during DRAINING. This additional state check is put in notify_xrun(), too.
Fixes: d5f871f89e21 ("ALSA: usb-audio: Improved lowlatency playback support") Reported-by: Leonard Crestez cdleonard@gmail.com Link: https://lore.kernel.org/25d5b0d8-4efd-4630-9d33-7a9e3fa9dc2b@gmail.com Link: https://patch.msgid.link/20241128080446.1181-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Sasha Levin sashal@kernel.org --- sound/usb/endpoint.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 8f65349a06d36..68aa174be12d7 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -403,10 +403,15 @@ static int prepare_inbound_urb(struct snd_usb_endpoint *ep, static void notify_xrun(struct snd_usb_endpoint *ep) { struct snd_usb_substream *data_subs; + struct snd_pcm_substream *psubs;
data_subs = READ_ONCE(ep->data_subs); - if (data_subs && data_subs->pcm_substream) - snd_pcm_stop_xrun(data_subs->pcm_substream); + if (!data_subs) + return; + psubs = data_subs->pcm_substream; + if (psubs && psubs->runtime && + psubs->runtime->state == SNDRV_PCM_STATE_RUNNING) + snd_pcm_stop_xrun(psubs); }
static struct snd_usb_packet_info * @@ -562,7 +567,10 @@ static void snd_complete_urb(struct urb *urb) push_back_to_ready_list(ep, ctx); clear_bit(ctx->index, &ep->active_mask); snd_usb_queue_pending_output_urbs(ep, false); - atomic_dec(&ep->submitted_urbs); /* decrement at last */ + /* decrement at last, and check xrun */ + if (atomic_dec_and_test(&ep->submitted_urbs) && + !snd_usb_endpoint_implicit_feedback_sink(ep)) + notify_xrun(ep); return; }