[alsa-devel] [RFC PATCH] Add combined clock support to Atmel SoC audio

[Ryan Mallon]

On 07/06/11 20:03, Sergey Lapin wrote:
> Hi, Ryan!
> 
> On Wed, Nov 24, 2010 at 11:05:11AM +1300, Ryan Mallon wrote:
>> The following patch is one that has been floating around in various
>> forms in our own internal trees for a while.
>>
>> The Atmel SSC peripheral has seperate TX and RX clocks which use
>> separate pins from the the micro. TF (frame) and TK (clock) for transmit
>> and RF and RK for receive. Not all codecs have separate frame and bit
>> clocks for transmit and receive so we want to be able to do both
>> playback and capture using a single set of pins.
>>
>> This patch introduces a combined clock mode for the Atmel SSC
>> peripheral. Which allows playback and capture to use a single set of
>> pins. Currently combined clock is only supported on the TF/TK pins (some
>> incomplete support exists for using RF/RK).
>>
>> I have tested this patch on our AT91SAM9G45 + TLV320AIC26 platform.
>> Playback and capture work individually. Simultaneous playback and
>> capture have been tested by connecting a loopback cable on the linein
>> and lineout jacks and then doing:
>>
>>   arecord -c 2 -f S16_LE -r 44100 > recording.wav &
>>   aplay 500hz_sine.wav
>>
>> This patch is posted as RFC since the approach is incomplete and a bit
>> hackish. I am mostly interested in knowing if this is a sensible
>> approach, and could be cleaned up for mainline inclusion, or if there is
>> a better way to do this.
>>
>> Signed-off-by: Ryan Mallon <ryan at bluewatersys.com>
> 
> I think it is also important to submit code, which uses it.
> If you can't do it I might try to do this in a few days.
> Also worth mentioning codec slave mode requirement for this to work.

Agreed. I don't have any hardware at the moment. I had intended to post
support for audio on the Bluewater Systems Snapper 9260 and 9G20 modules
(this patch being a precursor to that support), but I am no longer
working at Bluewater. Did you manage to get your hardware working in the
end?

I don't think the patch is ready for merging as is. It is incomplete
(though I suspect support for tx on the rx pins probably isn't needed)
and Mark also had some comments last time round: Use symmetric_rates,
replace atomic type with proper lock, etc. I think I may have done some
of this already, so can try and dig it out.

Also, this email address will cease to exist soon. Can you please use my
rmallon at gmail.com account instead. I'll have a kernel patch out soon to
fix my mail address up.

~Ryan