[alsa-devel] Please help in adding ams-delta support to ASoC

[Jarkko Nikula]

On Tue, 02 Jun 2009 15:35:10 +0200
Janusz Krzysztofik <jkrzyszt at tis.icnet.pl> wrote:

> I am not sure if this is of any importance, but with the old working 
> code, playing /dev/urandom to /dev/dsp I get only 3-4 DMA interrupts
> per second, while doing the same on a x86_64 via82cxxx results in
> 40-50 device interrupts per second.
> 
Looks like via specific since both OMAP3 Beagle and my desktop are
generating about 4 audio interrupts per second.

> I did not find any documentation on the codec itself, only on its 
> "master" modem chip cx81801. Regarding modem<->codec interface, there 
> were only pins with breif description specified for both chips,
> nothing more, as this interface was probably not intended for access
> from outside. From the codec side, it looks like this:
> 
> - Sleep (SLEEP); input
> - Master Clock (M_CLKIN); input
> - Serial Clock (M_SCK); output
> - Control (M_CNTRLSIN); input
> - Serial Frame Sync (M_STROBE); output
> - Serial Transmit Data (M_TXSIN); input
> - Serial Receive Data (M_RXOUT); output
> - Reset (POR); input
> 
> However, I can't tell which lines are switched from modem to mcbsp
> and which are kept connected to the modem chip all the time.
> Anyway, it looks like we can be sure that both bit clock and frame
> sync should come from codec to mcbsp. It is not clear for me if MCLK
> is really used by the codec, or it is possible that it gets its
> master clock from an other, modem related source, and if this does
> really matter.
> 
Hmm. Are there any possibility that ams_delta_latch2_write requires
working MCLK for latch change? I noticed that older implementation was
activating MCLK before latch and your ASoC patch does opposite. Sounds
a bit far but worth to try.

Probably you could use also older implementation to find out is the
MCLK required for codec by commenting out vc_mclk control.

> > At least one difference is that omap-mcbsp.c is constructing McBSP
> > register bits itself while older implementation was passing raw
> > register configuration from the board files. Probably you could try
> > to hack omap_mcbsp_dai_hw_params and pass the same register
> > settings there to see are there some missing bit in omap-mcbsp.c.
> 
> OK, I'll see if I know how to do this.
> 
Just hack the same "static struct omap_mcbsp_reg_cfg mcbsp_regs =
{ ..." in omap-mcbsp.c and pass that structure instead of
&mcbsp_data->regs to omap_mcbsp_config in omap_mcbsp_dai_hw_params.


-- 
Jarkko
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