From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolin Chen <nicoleotsuka@gmail.com>
Subject: Re: fsl_ssi.c: Roberto's problem: ssi hangs after some
 number of samples
Date: Wed, 4 Nov 2015 10:11:45 -0800
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To: Roberto Fichera <kernel@tekno-soft.it>
Cc: Fabio Estevam <fabio.estevam@freescale.com>, "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>, Shengjiu Wang <shengjiu.wang@freescale.com>, Caleb Crome <caleb@crome.org>, "arnaud.mouiche@invoxia.com" <arnaud.mouiche@invoxia.com>, Markus Pargmann <mpa@pengutronix.de>, "shawn.guo@linaro.org" <shawn.guo@linaro.org>, Fabio Estevam <festevam@gmail.com>
List-Id: alsa-devel@alsa-project.org

On Wed, Nov 04, 2015 at 06:52:12PM +0100, Roberto Fichera wrote:

> > I notice your DMA buffer length is very short, which would require
> > very frequency interrupts to service, right?   Can you increase your
> > DMA buffer length by increasing the period size?  Maybe that would
> > help reduce the likelyhood of a failure.  
> 
> Not sure if this can help! SSI TDM is set to 32 slots but only 2 are masked. So every frame only
> 2 slots are pushed/pulled from the FIFOs. maxburst is set to pull a block of 8 elements from the
> FIFOs, DMA cyclic call it period. So the full DMA buffer is filled in buffer size / period DMA iterations.

A smaller period size may course DMA buffer over/underrun -- ALSA
over/underrun even though it seems that you didn't report any.

And apparently SDMA would get more interrupt/callbacks. I would
suggest a larger period size and buffer size although I cannot
tie your problem with the size. But you may try.