Hi All,
I have recently noticed a problem with dwc2 and audio gadget.
The expected behavior:
The uac2 function acts as a kind of a pass-through.
For example to play audio from USB host on an Odroid U3 the following command
is issued at the host:
aplay -D plughw:CARD=Gadget,DEV=0 /usr/share/sounds/alsa/Front_Center.wav
while the following command is used at the device:
arecord -f dat -t wav -D plughw:CARD=UAC2Gadget,DEV=0 \|
aplay -D default:CARD=OdroidU3
At the device we "record" from the audio device provided by the usb gadget
and pipe the resulting stream to the actual hardware device present in
the chip on board.
What actually happens:
On recent kernels this does not work in a stable manner and sometimes
the kernel panics. I traced the problem back and it seems that the last
kernel without the below problems is 4.7.
I am using a compiled-in, legacy audio gadget with only uac2 function
selected in Kconfig.
4.7 works
4.8 kernel crashes at boot time
(bisect identifies 381fc8f8228923026b3d75c8230fa2ee4d688f32
"usb: dwc2: gadget: Add Incomplete ISO IN/OUT Interrupt handlers"),
compiling as a module does not help (crash at module load time),
composing the gagdet with configfs does not help either.
4.9 kernel crashes at boot time
4.10 kernel crashes at boot time
4.11 kernel crashes at boot time
4.12 kernel crashes at boot time
4.13 kernel crashes at boot time
4.14 kernel usually crashes at boot time, but sometimes it boots,
if it boots, it crashes the same way as at boot time when
the gadget is actually used (aplay at host and arecord | aplay
at the device)
4.15 kernel sometimes crashes at boot time, but otherwise it boots,
if it boots, it crashes the same way as at boot time when
the gadget is actually used (aplay at host and arecord | aplay
at the device)
4.16 kernel crashes at boot time
4.17 kernel sometimes crashes at boot time, but otherwise it boots,
if it boots, it crashes the same way as at boot time when
the gadget is actually used (aplay at host and arecord | aplay
at the device)
4.18 kernel sometimes crashes at boot time or even silently freezes,
but otherwise it boots, if it boots, it crashes the same way as
at boot time when the gadget is actually used (aplay at host
and arecord | aplay at the device)
4.19 and 4.20-rc4
kernel boots, but after some time the gadget stops working:
at the device with 4.19:
# arecord -f dat -t wav -D plughw:CARD=UAC2Gadget,DEV=0 | aplay -D
default:CARD=OdroidU3
Recording WAVE 'stdin' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
Playing WAVE 'stdin' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
[ 26.245056] max98090 1-0010: PLL unlocked
underrun!!! (at least 1256.128 ms long)
[ 29.363400] max98090 1-0010: PLL unlocked
underrun!!! (at least 930.612 ms long)
underrun!!! (at least 447.733 ms long)
[ 34.475390] max98090 1-0010: PLL unlocked
underrun!!! (at least 319.622 ms long)
[ 36.678554] max98090 1-0010: PLL unlocked
underrun!!! (at least 611.690 ms long)
[ 39.153660] max98090 1-0010: PLL unlocked
underrun!!! (at least 724.196 ms long)
[ 41.741488] max98090 1-0010: PLL unlocked
underrun!!! (at least 695.816 ms long)
[ 44.428490] max98090 1-0010: PLL unlocked
underrun!!! (at least 795.061 ms long)
[ 47.106276] max98090 1-0010: PLL unlocked
underrun!!! (at least 760.757 ms long)
underrun!!! (at least 2685.446 ms long)
[ 54.288479] max98090 1-0010: PLL unlocked
underrun!!! (at least 1591.909 ms long)
[ 57.764445] max98090 1-0010: PLL unlocked
underrun!!! (at least 223.942 ms long)
underrun!!! (at least 237.751 ms long)
[ 61.974963] max98090 1-0010: PLL unlocked
underrun!!! (at least 677.925 ms long)
[ 64.645406] max98090 1-0010: PLL unlocked
underrun!!! (at least 550.651 ms long)
[ 67.079379] max98090 1-0010: PLL unlocked
underrun!!! (at least 1575.582 ms long)
[ 70.521155] max98090 1-0010: PLL unlocked
underrun!!! (at least 832.604 ms long)
[ 73.219814] max98090 1-0010: PLL unlocked
underrun!!! (at least 721.516 ms long)
while at the host:
$ aplay -D plughw:CARD=Gadget,DEV=0 /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little
Endian, Rate 48000 Hz, Mono
.... several times ok ....
$ aplay -D plughw:CARD=Gadget,DEV=0 /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little
Endian, Rate 48000 Hz, Mono
aplay: set_params:1297: Unable to install hw params:
ACCESS: RW_INTERLEAVED
FORMAT: S16_LE
SUBFORMAT: STD
SAMPLE_BITS: 16
FRAME_BITS: 16
CHANNELS: 1
RATE: 48000
PERIOD_TIME: 125000
PERIOD_SIZE: 6000
PERIOD_BYTES: 12000
PERIODS: 4
BUFFER_TIME: 500000
BUFFER_SIZE: 24000
BUFFER_BYTES: 48000
TICK_TIME: 0
Any ideas on how to test it further to identify the problem?
Definitely the commit identified with bisect was a problem at least
until 4.13. Perhaps it still is the root cause, but I can't tell.
It is difficult to revert it, because there were later changes which
depend on it.
Andrzej
