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

Grant Likely grant.likely at secretlab.ca
Thu Jul 3 18:30:00 CEST 2008


On Wed, Jul 02, 2008 at 11:19:18AM -0400, Jon Smirl wrote:
> On 7/1/08, Grant Likely <grant.likely at secretlab.ca> wrote:
> >  +               /* Due to errata in the i2s mode; need to line up enabling
> >  +                * the transmitter with a transition on the frame sync
> >  +                * line */
> >  +
> >  +               spin_lock_irqsave(&psc_i2s->lock, flags);
> >  +               /* first make sure it is low */
> >  +               while ((in_8(&regs->ipcr_acr.ipcr) & 0x80) != 0);
> 
> Could this be moved to the front of the routine, to increase parallelism?
> 
> Once you detect the 0, it will be a fixed interval before the 1
> happens. Might as well overlap the computations.
> 

Good point.  I'll try this out and see if it remains stable.  If this
gets done wrong, then left and right channels will often get swapped.

g.


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