[alsa-devel] [PATCH] ASoC: DaVinci: Added support for cpu clocking I2S
lamiaposta71 at gmail.com
Wed Jun 30 10:17:40 CEST 2010
2010/6/28 Mark Brown <broonie at opensource.wolfsonmicro.com>
> On Mon, Jun 28, 2010 at 08:44:46AM +0200, Raffaele Recalcati wrote:
> > From: Raffaele Recalcati <raffaele.recalcati at bticino.it>
> It's still very hard to understand what this patch is supposed to do.
> As previously mentioned this would probably be a lot clearer if you
> split this into multiple patches, for example one adding support for the
> fast clock mode, one adding support for selecting the pin used for any
> external clock and then further patches with any other changes.
Looking at other paches, they are simpler than mine.
I'll try to split it, hoping to obtain the final result.
> I strongly suggest looking at the commit messages for other patches in
> the kernel and trying to follow a similar style.
> > Added audio playback support with [frame sync master - clock master]
> > and with [frame sync master - clock slave].
> What are these modes - which clock are you talking about?
McBSP i2s interface to external codec.
> > i2s_fast_clock switch can be used to have better approximate or
> > symmetric waveforms.
> Why would someone choose not to use this?
I was not sure if symmetric waveform can be a must.
In general I think it is better a non symmetric, but better approximate,
Anyway, it is better to have the possibility to choose in my opinion,
because I have not so much experience in i2s communication.
> > clk_input_pin board info can be used to select it depending on hw
> > connections
> > 3. We haven't changed the evmdm365 support (due also to CPLD that
> > help to understand)
> > We don't know in this mode if audio stereo works on evmdm365.
> > Probably it does.
> This is what makes me unsure if you're trying to add new modes or not -
> if you're adding new modes then I'd expect that existing boards would be
> unaffected with any changes to use the new feature being easily
Some tests are needed, but it requires time.
I'll try try to make some tests on evmdm365, but I'm not sure to have time
to do it.
> > + /*
> > + * This define works when both clock and FS are output for the cpu
> > + * and makes clock very fast (FS is not simmetrical, but sampling
> > + * frequency is better approximated
> > + */
> > + int i2s_fast_clock;
> Is this a bool?
yes, I'll change it.
> > + /* To be used when cpu gets clock from extenal pin */
> > + int clk_input_pin;
> > +
> How would one use this?
looking at 2.5 Clock, Frames, and Data in
you can select MCBSP_CLKS or other input clock pins.
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