Hello,
i'm fighting with audio playback problem on Beaglebone Black AM-3358.
Class compilant USB soundcards with isochronous transfers.
With DMA enabled in kernels 3.13.2 and 3.14-rc2 it has following symptoms.
- it will stutter immediately after starts of playback
- kworker thread shows about 80-90% CPU usage during playback
- it presents with cppi41_dma_control warnings and traces, plus couple
of transfer errors
(i've enabled also CONFIG_DMADEVICES_DEBUG, so it dmesg is quite lengthy)
http://vpub.smucr.cz/pub/bbb/debug/dmesg.log
With force PIO at any tested kernel from 3.8.x to 3.14.x and DMA mode at
3.12.9 it is better, CPU load seems to be much lower, but it is not
completely solved. Still during high interrupt load from other devices
like NIC or second USB port, i'm having audio dropouts. Without any
messages this time.
I tested to apply following George Cherian's related patches
http://marc.info/?l=linux-usb&m=139081552015728&w=2
usb: musb: musb_host: Enable ISOCH IN handling for AM335x host
usb: musb: musb_cppi41: Make CPPI aware of high bandwidth transfers
usb: musb: musb_cppi41: Handle ISOCH differently and not use the hrtimer
and Adam Wozniak's
http://marc.info/?l=linux-usb&m=139101388408467&w=2
"high cpu load on omap3 using musb"
But it haven't changed anything for that issue.
Thank you for help,
Michal
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