[alsa-devel] [PATCH 2/3] ALSA SoC: Add mpc5200-psc I2S driver

[Jon Smirl]

On 7/7/08, Mark Brown <broonie at opensource.wolfsonmicro.com> wrote:
> On Sun, Jul 06, 2008 at 01:56:48PM -0400, Jon Smirl wrote:
>
>  > The driver is assuming a capture stream exists. My codec is output only.
>
>
> While the driver declares a capture stream the core doesn't require that
>  both capture and playback be available - it will cope with a capture
>  only or a playback only DAI (this is fairly common due to DAC only and
>  ADC only parts).  Unless there's some other issue specific to this
>  driver?

Yes, it GPFs allocating a a DMA buffer on the null capture stream pointer.

>
>  > I'm using external clocking, but the driver should support using the
>  > mpc5200 for clocking. That's a little complicated since you have to
>  > compute the divisors. For example the Phytec pcm030 board has a
>  > 33.3333Mhz xtal and runs at 400Mhz.
>
>
> This is desirable, though it shouldn't be an obstacle for merging if the
>  driver only supports running in slave mode.
>
>
>  > In order to reduce options, can the psc-i2s driver always try to use
>  > mpc5200 clocking, then let the codec or fabric driver override it?
>
>
> The clocking should always be under the control of the machine driver
>  with the codec and platform drivers exporting the required dividers and
>  PLLs/FLLs.  Neither the platform driver nor the codec driver are really
>  in a position to know how a given board is wired up and what
>  interdependencies or external requirements there are.
>


-- 
Jon Smirl
jonsmirl at gmail.com