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linux-stable/sound/usb
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Takashi Iwai 9ce650a75a ALSA: usb-audio: Reduce latency at playback start 
USB-audio driver behaves a bit strangely for the playback stream --
namely, it starts sending silent packets at PCM prepare state while
the actual data is submitted at first when the trigger START is kicked
off.  This is a workaround for the behavior where URBs are processed
too quickly at the beginning.  That is, if we start submitting URBs at
trigger START, the first few URBs will be immediately completed, and
this would result in the immediate period-elapsed calls right after
the start, which may confuse applications.

OTOH, submitting the data after silent URBs would, of course, result
in a certain delay of the actual data processing, and this is rather
more serious problem on modern systems, in practice.

This patch tries to revert the workaround and lets the URB submission
starting at PCM trigger for the playback again.  As far as I've tested
with various backends (native ALSA, PA, JACK, PW), I haven't seen any
problems (famous last words :)

Note that the capture stream handling needs no such workaround, since
the capture is driven per received URB.

Link: https://lore.kernel.org/r/20210601162457.4877-6-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2021-06-02 09:02:06 +02:00
..
6fire module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
bcd2000 ALSA: Convert strlcpy to strscpy when return value is unused 2021-01-08 09:30:05 +01:00
caiaq module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
hiface module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
line6 sound: line6: move to use usb_control_msg_send() and usb_control_msg_recv() 2020-09-25 16:33:59 +02:00
misc module: remove never implemented MODULE_SUPPORTED_DEVICE 2021-03-17 13:16:18 -07:00
usx2y Merge branch 'topic/pci-rescan-prep-v2' into for-next 2021-05-25 08:50:03 +02:00
card.c ALSA: usb-audio: Skip probe of UA-101 devices 2021-04-09 09:57:30 +02:00
card.h ALSA: usb-audio: Refactoring delay account code 2021-06-02 09:01:44 +02:00
clock.c ALSA: usb-audio: Fix uninitialized variable at __uac_clock_find_source() 2021-05-21 16:16:21 +02:00
clock.h ALSA: usb-audio: Constify audioformat pointer references 2020-11-23 15:15:36 +01:00
endpoint.c ALSA: usb-audio: Refactoring delay account code 2021-06-02 09:01:44 +02:00
endpoint.h ALSA: usb-audio: Remove the repeated declaration 2021-05-30 09:30:46 +02:00
format.c ALSA: usb-audio: workaround for iface reset issue 2021-01-23 16:59:42 +01:00
format.h ALSA: usb: initial USB Audio Device Class 3.0 support 2018-03-21 11:46:33 +01:00
helper.c ALSA: usb-audio: Add snd_usb_get_host_interface() helper 2020-11-23 15:13:47 +01:00
helper.h ALSA: usb-audio: Add snd_usb_get_host_interface() helper 2020-11-23 15:13:47 +01:00
implicit.c ALSA: usb-audio: Generic application of implicit fb to Roland/BOSS devices 2021-04-22 18:19:47 +02:00
implicit.h ALSA: usb-audio: Factor out the implicit feedback quirk code 2020-11-23 15:17:00 +01:00
Kconfig sound: Fix Kconfig indentation 2019-10-07 03:53:03 +02:00
Makefile ALSA: usb-audio: Factor out the implicit feedback quirk code 2020-11-23 15:17:00 +01:00
media.c media: sound/usb: Use Media Controller API to share media resources 2019-04-22 11:21:06 -04:00
media.h media: sound/usb: Use Media Controller API to share media resources 2019-04-22 11:21:06 -04:00
midi.c ALSA: usb-audio: Fix potential out-of-bounce access in MIDI EP parser 2021-05-11 11:10:37 +02:00
midi.h ALSA: usb-audio: generate midi streaming substream names from jack names 2021-03-01 09:21:54 +01:00
mixer.c ALSA: usb-audio: Remove redundant assignment to len 2021-04-28 12:07:39 +02:00
mixer.h ALSA: usb-audio: Check connector value on resume 2021-03-26 09:10:33 +01:00
mixer_maps.c ALSA: usb-audio: Add dB range mapping for Sennheiser Communications Headset PC 8 2021-05-03 13:35:58 +02:00
mixer_quirks.c ALSA: control - add generic LED API 2021-03-30 17:42:40 +02:00
mixer_quirks.h ALSA: usb-audio: Initialize Dell Dock playback volumes 2018-05-02 16:02:32 +02:00
mixer_s1810c.c ALSA: usb-audio: Fix some typos 2020-06-30 19:48:18 +02:00
mixer_s1810c.h ALSA: usb-audio: Add support for Presonus Studio 1810c 2020-02-15 09:46:16 +01:00
mixer_scarlett.c ALSA: Convert strlcpy to strscpy when return value is unused 2021-01-08 09:30:05 +01:00
mixer_scarlett.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mixer_scarlett_gen2.c ALSA: Convert strlcpy to strscpy when return value is unused 2021-01-08 09:30:05 +01:00
mixer_scarlett_gen2.h ALSA: usb-audio: Scarlett Gen 2 mixer interface 2019-07-28 17:47:48 +02:00
mixer_us16x08.c ALSA: Convert strlcpy to strscpy when return value is unused 2021-01-08 09:30:05 +01:00
mixer_us16x08.h ALSA: usb: Constify snd_kcontrol_new items 2020-01-03 09:24:34 +01:00
pcm.c ALSA: usb-audio: Reduce latency at playback start 2021-06-02 09:02:06 +02:00
pcm.h ALSA: usb-audio: Make snd_usb_pcm_delay() static 2021-06-02 09:01:17 +02:00
power.c ALSA: usb-audio: More validations of descriptor units 2019-08-22 10:35:59 +02:00
power.h ALSA: usb-audio: Initial Power Domain support 2018-07-31 15:01:22 +02:00
proc.c ALSA: usb-audio: Show sync endpoint information in proc outputs 2020-11-23 15:16:45 +01:00
proc.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
quirks-table.h ALSA: usb-audio: Add MIDI quirk for Vox ToneLab EX 2021-04-09 09:58:13 +02:00
quirks.c ALSA: usb-audio: DJM-750: ensure format is set 2021-04-19 09:42:35 +02:00
quirks.h ALSA: usb-audio: Constify audioformat pointer references 2020-11-23 15:15:36 +01:00
stream.c Merge branch 'for-linus' into for-next 2020-12-14 09:05:29 +01:00
stream.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
usbaudio.h ALSA: usb-audio: Apply implicit feedback mode for BOSS devices 2021-04-14 14:24:22 +02:00
validate.c ALSA: usb-audio: Fix endianess in descriptor validation 2020-02-01 09:06:11 +01:00