[alsa-devel] davici-mcasp: "tx-num-evt" confusion with number of serializers
michal.bachraty at streamunlimited.com
Tue Feb 26 15:06:54 CET 2013
I'm working on multichannel version of davinci-mcasp and also davinci-pcm. I
have first version running and now I want to refine code. I found one confusion
in davinci-mcasp with using of DT property "tx-num-evt". In DT binding
documentation "tx-num-evt" is defined as "FIFO levels", but in Mcasp src, there
is code, which mixes tx-num-evt with number of serializers (i2s data lines)
that are enabled for data playback and receive (dev->txnumevt * tx_ser)
mcasp_mod_bits(dev->base + MCASP_VER3_WFIFOCTL,
(((dev->txnumevt * tx_ser) << 8), NUMEVT_MASK);
>From dacinci pcm, DMA data tranfer use txnumevt as number of serializers and
also for data prefetching.
I undestand definition "FIFO levels" as how many prefetched data are in FIFO.
Prefetched data are for me frame data / 2 ( all left or right channels for
one sampling time). This results me from AM335x FIFO documantation.
What is original purpose for "tx-num-evt" parameter?
More information about the Alsa-devel