[alsa-devel] [PATCH 2/2] ASoC: fsl_ssi: Fix number of words per frame for I2S-slave mode

[Nicolin Chen]

On Tue, Jun 28, 2016 at 10:59:32PM +0300, Alexander Shiyan wrote:
> >Вторник, 28 июня 2016, 21:20 +03:00 от Nicolin Chen <nicoleotsuka at gmail.com>:
> >
> >On Sat, Jun 25, 2016 at 07:59:22AM +0300, Alexander Shiyan wrote:
> >> The i.MX51 datasheet says:
> >> Chapter 56.1.2.4 I2S Mode
> >> ...
> >> When I2S modes are entered (I2S master (01) or I2S slave (10)),
> >> the following settings are recommended:
> >> ...
> >> - TX Frame Rate should be 2 i.e. (STCCR[12:8] = 1)
> >> - RX Frame Rate should be 2 i.e. (SRCCR[12:8] = 1)
> >> 
> >> Chapter 56.3.3.12 SSI Transmit and Receive Clock Control Registers (STCCR & SRCCR)
> >> ...
> >> Bits 12-8 DC4-DC0
> >> Frame Rate Divider Control. These bits are used to control the divide ratio
> >> for the programmable frame rate dividers. The divide ratio works on the word
> >> clock. In Normal mode, this ratio determines the word transfer rate.
> >> In Network mode, this ratio sets the number of words per frame. The divide
> >> ratio ranges from 1 to 32 in Normal mode and from 2 to 32 in Network mode.
> >> In Normal mode, a divide ratio of 1 (DC=00000) provides continuous periodic
> >> data word transfer. A bit-length frame sync must be used in this case.
> >> 
> >> Function fsl_ssi_hw_params() setup Normal mode for MONO output,
> >> so with DC=0, SSI enters to continuous periodic data word transfer.
> >> To fix this, setup DC for any I2S mode.
> >
> >The change looks fine and didn't show any problem when I tested it.
> >But I am wondering what's the failed user case here so we need this
> >patch to fix? (The mono playback works without this patch as well.)
> 
> Probably this works fine without patch if FSclk == BITclk * size.

I acked this patch since it's more likely a correct configuration
according to the reference manual while still want to know what's
your failed case. Could you please tell me what were the FSclk,
BITclk and size of your case?

Thanks
Nicolin