[alsa-devel] SGTL500 and its external MCLK

[jonsmirl at gmail.com]

On Fri, Aug 8, 2014 at 1:29 AM, Nicolin Chen <Guangyu.Chen at freescale.com> wrote:
> On Thu, Aug 07, 2014 at 03:37:47PM -0400, jonsmirl at gmail.com wrote:
>> Since the sgtl5000 driver has the handle to the clock, can't it just
>> ask the clock for its rate? If it directly asked the clock for its
>> rate it looks like this codec could be bound with simple-audio-card
>> and not need a machine driver.
>
> I think Simple Card should already have the capability to support
> this without changing sgtl5000's code. It has two properties that
> can make it call set_sysclk() for you during the init(). They are
> 'clocks' and 'system-clock-frequency'. Please refer to its binding
> doc for details.
>
> And the topic why not let sgtl5000 fully control the clock has been
> discussed in this thread:
> http://comments.gmane.org/gmane.linux.alsa.devel/109093
>
> So I think the change can be done as well?

I tried hacking on it some. One problem is with clocks that aren't
100% accurate. For example my clock is off a little - 22.571428. So
when the code divides that by 44100 it gets 511.8 which truncates to
511 and the test for equal to 512 fails.


>
> Best regards,
> Nicolin



-- 
Jon Smirl
jonsmirl at gmail.com