[alsa-devel] Driver code with mpc5200 pointer problem.

[Takashi Iwai]

At Tue, 28 Apr 2009 10:00:02 +0100,
Mark Brown wrote:
> 
> On Tue, Apr 28, 2009 at 08:08:06AM +0200, Takashi Iwai wrote:
> > Mark Brown wrote:
> 
> > > On Mon, Apr 27, 2009 at 05:09:27PM +0200, Jaroslav Kysela wrote:
> 
> > > > Appearently, FIFO is too big. I'm working on some changes to take account 
> 
> > > Could you expand a bit on what qualifies as "too big" here?  I've not
> > > been following the thread here or the changes that caused problems.
> 
> > It's bigger than the pre-defined tolerance of jiffies check in PCM
> > core code.
> 
> Hrm, OK.  That may create problems for some embedded systems which can
> use very large FIFOs (well, FIFO equivalents) to allow the processor to
> go to sleep when doing things like MP3 playback.  I don't think any of
> those have audio support in mainline yet, though.
> 
> > The new PCM core checks the returned hw_ptr together with jiffies
> > delta whether it's a sane value.  When FIFO is used with the ring
> > buffer, the hardware tends to report back earlier before the expected
> > timing.
> 
> But (from other messages in the thread) it's possible to disable these
> checks if required?

That's being discussed now :)


Takashi