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| author | Takashi Iwai <tiwai@suse.de> | 2021-08-29 09:38:30 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2021-08-29 09:41:27 +0200 |
| commit | 4801bee7d5a36c199b734a28cde5259183aff822 (patch) | |
| tree | 106e13cacf6d6263316ff0147734465037e90cd8 /sound/usb | |
| parent | 4267c5a8f3133db0572cd9abee059b42cafbbdad (diff) | |
| download | lwn-4801bee7d5a36c199b734a28cde5259183aff822.tar.gz lwn-4801bee7d5a36c199b734a28cde5259183aff822.zip | |
ALSA: usb-audio: Add lowlatency module option
For making user to switch back to the old playback mode, this patch
adds a new module option 'lowlatency' to snd-usb-audio driver.
When user face a regression due to the recent low-latency playback
support, they can test easily by passing lowlatency=0 option without
rebuilding the kernel.
Fixes: 307cc9baac5c ("ALSA: usb-audio: Reduce latency at playback start, take#2")
Link: https://lore.kernel.org/r/20210829073830.22686-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb')
| -rw-r--r-- | sound/usb/card.c | 4 | ||||
| -rw-r--r-- | sound/usb/pcm.c | 3 | ||||
| -rw-r--r-- | sound/usb/usbaudio.h | 1 |
3 files changed, 7 insertions, 1 deletions
diff --git a/sound/usb/card.c b/sound/usb/card.c index a1f8c3a026f5..6abfc9d079e7 100644 --- a/sound/usb/card.c +++ b/sound/usb/card.c @@ -68,6 +68,7 @@ static int pid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 }; static int device_setup[SNDRV_CARDS]; /* device parameter for this card */ static bool ignore_ctl_error; static bool autoclock = true; +static bool lowlatency = true; static char *quirk_alias[SNDRV_CARDS]; static char *delayed_register[SNDRV_CARDS]; static bool implicit_fb[SNDRV_CARDS]; @@ -92,6 +93,8 @@ MODULE_PARM_DESC(ignore_ctl_error, "Ignore errors from USB controller for mixer interfaces."); module_param(autoclock, bool, 0444); MODULE_PARM_DESC(autoclock, "Enable auto-clock selection for UAC2 devices (default: yes)."); +module_param(lowlatency, bool, 0444); +MODULE_PARM_DESC(lowlatency, "Enable low latency playback (default: yes)."); module_param_array(quirk_alias, charp, NULL, 0444); MODULE_PARM_DESC(quirk_alias, "Quirk aliases, e.g. 0123abcd:5678beef."); module_param_array(delayed_register, charp, NULL, 0444); @@ -599,6 +602,7 @@ static int snd_usb_audio_create(struct usb_interface *intf, chip->setup = device_setup[idx]; chip->generic_implicit_fb = implicit_fb[idx]; chip->autoclock = autoclock; + chip->lowlatency = lowlatency; atomic_set(&chip->active, 1); /* avoid autopm during probing */ atomic_set(&chip->usage_count, 0); atomic_set(&chip->shutdown, 0); diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index f5cbf61ac366..5dc9266180e3 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -617,7 +617,8 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream) /* check whether early start is needed for playback stream */ subs->early_playback_start = subs->direction == SNDRV_PCM_STREAM_PLAYBACK && - subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes; + (!chip->lowlatency || + (subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes)); if (subs->early_playback_start) ret = start_endpoints(subs); diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h index 538831cbd925..8b70c9ea91b9 100644 --- a/sound/usb/usbaudio.h +++ b/sound/usb/usbaudio.h @@ -57,6 +57,7 @@ struct snd_usb_audio { bool generic_implicit_fb; /* from the 'implicit_fb' module param */ bool autoclock; /* from the 'autoclock' module param */ + bool lowlatency; /* from the 'lowlatency' module param */ struct usb_host_interface *ctrl_intf; /* the audio control interface */ struct media_device *media_dev; struct media_intf_devnode *ctl_intf_media_devnode; |