Hi George,
I did few more tests and have further details for you.
This time i modified my build procedure and according to Felipe's hint,
I used ti-linux-3.12.y branch from TI repository and also clean 3.14-rc6
kernel, where i subsequently tried additional unmerged patches.
With ti-linux-3.12.y I didn't notice any of CPU usage or stability,
80-90%, dropouts.
Latest kernel behaved differently, CPU usage is low and audio after DAC
is total rubbish (constant level noise).
After playing with additional patches, i've found, that modifications in
your third patch for different isochronous packet handling
https://lkml.org/lkml/2014/1/24/187
causes high load.
So it looks like, without this patch, hrtimer trick for compensation of
early interrupt doesn't work and samples gets garbled during transfers
(albeit i don't have HW USB analyzer to prove it). Alternative with fifo
checking and workqueue, unfortunately hogs CPU.
Thanks,
Michal
On 27.2.2014 12:18, Michal Šmucr wrote:
Hi George,
On 27.2.2014 5:15, George Cherian wrote:
I too see the backtraces will send a patch soon to fix the same.
Thanks, i applied it and most of backtraces was suppressed.
Several times i was able to invocate it again, but this time, it was
before complete stuck of playback application (kill -9 was only way to
end it).
From that moment, no other audio playback can be initiated until next
reboot. If i tried to remedy situation by replugging of USB interface,
it leaded to nice Oops (snippet from serial console is attached).
During my testing am not seeing the CPU usage as you mention.
That is interesting, i was able to reproduce it whenever i tried that,
maybe it could be also some config issue.
Just for more complete info, i'm using build scripts by Robert C. Nelson
and there are couple other patches applied to kernel before build (now
including your previous ISOCH. handling ones) -
https://github.com/RobertCNelson/linux-dev/tree/am33x-v3.14/patches ,
but it doesn't seems related to issue.
Could you please share you .config.
You'll find it attached.
I used aplay for testing playback and arecord for recording using USB
headsets.
I tried mpd as player, but i'm able to reproduce kworker load also with
aplay or alsa built-in speaker-test (eg. speaker-test -c 2 -D plughw:0,0).
Regarding hardware i tried few XMOS based UAC2 interfaces and recently
also interface with TI PCM2904 USB codec, which could be very close to
headset, you tried. It doesn't matter according to my tests.
Thanks,
Michal
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