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kernel 3.14, audio clocks and sample rates issues

Question asked by Angelo Dureghello on Aug 19, 2015
Latest reply on May 24, 2016 by Angelo Dureghello
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Hi all,

 

i moved from kernel 3.10 to 3.14 in a very similar sabre-auto board.

 

With this kernel I am having some new issues when i redirect audio from radio chip (silabs si4745, 32Khz master clock) to the cs42888 output codec.

Mainly,

- pulseaudio: sinks don't like 44100 as default-sample-rate, while audio is good at 48000Hz.

- alsa tests, similar issues:

arecord --device=default:CARD=imxaudiosi4745 | aplay --device=default:CARD=cs42888audio (8khz sample rate, OK, GOOD)

arecord -r 48000 --device=default:CARD=imxaudiosi4745 | aplay --device=default:CARD=cs42888audio    OK, GOOD

arecord -r 44100 --device=default:CARD=imxaudiosi4745 | aplay --device=default:CARD=cs42888audio

overrun!!! (at least 12.157 ms long)

 

Also, when i use alsa and set as output the HDMI (FM radio to HDMI), i get continuosly "underrun" messages and audio cuts. In this case, using pulseaudio gives a good quality, but audio is delayed of some seconds, probably used from pulseaudio as a buffer to avoid underrun.

 

Something seems connected to the FM radio master clock, like seems multiples of 8Khz works fine (FM chip uses 32768 master clock).

 

What i miss actually is:

- sample rate: it is decided from the sampling source. Why must be set in the output device and it don't adapt automatically to the source sample rate ?

 

In kernel 3.14 device tree there are new &clk {} entries to be set (i copied them , from sabreauto), and this make me suspect it is connected to the issue i am having.

 

Every light on this is welcome.

Thanks & Best regards

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