Sorry if this is inappropriate place for posting kernel bugs - I've tried to reach Freescale audio maintainer (Li.Xiubo) but his email bouncing messages - please point me to the right place if so.
I'm using the DART-6UL kit with IMX6UL CPU and found three kernel problems with audio :
1. The raw audio device can be opened only at 44100 sampling rate. This means that all other rates must be used through plughw interface which leads to CPU consuming software resampling. This line of code at fsl_sai.c:fsl_sai_set_bclk() prevents other rates :
if (ret != 0 && clk_rate / ret < 1000)
It is interesting where is the magic value 1000 from ?
2. If you try to open the raw audio using other than 44100 sample rate (aplay -r 8000 -c 1 -D hw:CARD=wm8731audio,DEV=0 some.wav) you will have the kernel error message and unusable audio until next reboot :
[ 79.501506] fsl-sai 202c000.sai: ASoC: 202c000.sai hw params failed: -22
As I can see all other subsequent audio openings are made with 48000Hz(?!) sample rate and fail despite correct settings.
3. I've got total system freeze several times with infinite debug console scrolling lines about audio interrupts overrun. I still can't reproduce this but in this state the board do not respond to pings or console commands.
I will be appreciated if somebody can point me to the imx audio kernel developer or fix this issues.