[alsa-devel] [PATCH v3 1/3] ASoC: davinci-mcasp: Constraint on the period and buffer size based on FIFO usage

Peter Ujfalusi peter.ujfalusi at ti.com
Wed Mar 19 12:13:50 CET 2014

On 03/18/2014 08:07 PM, Mark Brown wrote:
> On Tue, Mar 18, 2014 at 04:28:55PM +0200, Peter Ujfalusi wrote:
>> On 03/18/2014 03:23 PM, Peter Ujfalusi wrote:
>>> Oh, I edited the commit message and removed the text related to buffer size
>>> but I failed to do that for the commit title :(
>> Actually I still have issue with the constraint.
> OK, so is the patch an improvement or not?  If it fixes some cases it's
> probably worth applying even if further fixes are still needed.

Some application might fail (like mplayer with 44.1KHz) with constraint on the
period size only. Without the constraint we will have constant pops at every
period when non aligned size has been selected - if the FIFO depth is
configured to more than 1, which is not yet the case in upstream.

> No need to resend for the subject, I can fix that up.
>> It seams that I need to place the same constraint step to both period size and
>> buffer size.
>> For some reason snd_pcm_hw_params_set_buffer_time_near() fails in case of
>> 44.1KHz when asking for 0.5s buffer when I placed step 32 constraint to period
>> size. Placing the same 32 steps constraint to the buffer size as well will
>> make things working (for mplayer at least)
> That seems like the constraint code is failing, at a guess probably
> looking for too near a value of near if you see what I mean.  I don't
> really have the time/enthusiasm to investigate this right now, sorry.

Yep, this needs to be investigated. Me or Jyri will take a look at this for
sure since it is somehow odd.


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