linux-kernel - Re: [alsa-devel] looping S/PDIF data

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Date:	Thu, 19 Jun 2008 14:48:19 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Jaroslav Kysela <perex@...ex.cz>
Cc:	Rene Herman <rene.herman@...access.nl>,
	ALSA devel <alsa-devel@...a-project.org>, mulix@...ix.org,
	Pierre Ossman <drzeus@...eus.cx>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [alsa-devel] looping S/PDIF data

At Thu, 19 Jun 2008 14:39:05 +0200 (CEST),
Jaroslav Kysela wrote:
> 
> On Thu, 19 Jun 2008, Takashi Iwai wrote:
> 
> > At Wed, 18 Jun 2008 09:24:59 +0200,
> > Rene Herman wrote:
> > > 
> > > On 17-06-08 21:55, Pierre Ossman wrote:
> > > 
> > > > Ping
> > > > 
> > > > On Sat, 31 May 2008 11:26:06 +0200
> > > > Pierre Ossman <drzeus-list@...eus.cx> wrote:
> > > > 
> > > >> I have a minor annoyance with the snd_trident driver that I was hoping
> > > >> you might have a fix for:
> > > >>
> > > >> Pausing the output does not seem to take on the S/PDIF output. Analog
> > > >> outputs properly stop in their tracks, but the S/PDIF port keeps
> > > >> looping the current data buffer, which gives a rather unpleasant end
> > > >> result. :)
> > > 
> > > Try the alsa-devel list...
> > 
> > Does the patch below help?
> > 
> > 
> > Takashi
> > 
> > diff --git a/sound/pci/trident/trident_main.c b/sound/pci/trident/trident_main.c
> > index bbcee2c..916d4b8 100644
> > --- a/sound/pci/trident/trident_main.c
> > +++ b/sound/pci/trident/trident_main.c
> > @@ -1593,7 +1593,11 @@ static int snd_trident_trigger(struct snd_pcm_substream *substream,
> >  			outb(trident->spdif_pcm_ctrl, TRID_REG(trident, NX_SPCTRL_SPCSO + 3));
> >  		} else {
> >  			outl(trident->spdif_pcm_bits, TRID_REG(trident, SI_SPDIF_CS));
> > -			val = inl(TRID_REG(trident, SI_SERIAL_INTF_CTRL)) | SPDIF_EN;
> > +			val = inl(TRID_REG(trident, SI_SERIAL_INTF_CTRL));
> > +			if (go)
> > +				val |= SPDIF_EN;
> > +			else
> > +				val &= ~SPDIF_EN;
> >  			outl(val, TRID_REG(trident, SI_SERIAL_INTF_CTRL));
> >  		}
> >  	}
> 
> I don't think that this patch is correct. DMA transfers should be disabled 
> by:
> 
> outl(what, TRID_REG(trident, T4D_STOP_B));
> outl(val, TRID_REG(trident, T4D_AINTEN_B));

They are already in the trigger callback as long as I saw the code
quickly.  So the problem should be somewhere else.

> lines. Adding &= ~SPDIF_EN can disable output from AC97 to S/PDIF as well.

That's true.

Anyway, if you are up now, I'll let you hunt further as you are the
author of the driver :)


thanks,

Takashi
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