Re: fsl_ssi.c: Getting channel slips with fsl_ssi.c in TDM (network) mode.

[Nicolin Chen <nicoleotsuka@gmail.com>]

On Tue, Oct 27, 2015 at 08:13:44AM +0100, Markus Pargmann wrote:

> > So, the dma priority doesn't seem to be the issue.  It's now set in
> > the device tree, and strangely it's set to priority 0 (the highest)
> > along with the UARTS.  priority 0 is just the highest in the device
> > tree -- it gets remapped to priority 3 in the sdma driver.  the DT
> > exposes only 3 levels of DMA priority, low, medium, and high.  I
> > created a new level that maps to DMA priroity 7 (the highest in the
> > hardware), but still got the problem.
> > 
> > So, still something unknown causing dma to miss samples.  must be in
> > the dma ISR I would assume.  I guess it's time to look into that.

> Cc Nicolin, Fabio, Shawn
> 
> Perhaps you have an idea about this?

Off the top of my head:

1) Enable TUE0, TUE1, ROE0, ROE1 to see if there is any IRQ trigged.

2) Set the watermarks for both TX and RX to 8 while using burst sizes
   of 6. It'd be nicer to provisionally set these numbers using hard
   code than your current change depending on fifo_depth as it might
   be an odd value.

3) Try to enlarge the ALSA period size in the asound.conf or passing
   parameters when you do the playback/capture so that the number of
   interrupts from SDMA may reduce.

You may also see if the reproducibility is somehow reduced or not.

Nicolin