[alsa-devel] [PATCH 2/2] ALSA: hda: fix to wait for RIRB & CORB DMA to set

[Takashi Iwai]

On Thu, 28 Apr 2016 15:55:54 +0200,
Vinod Koul wrote:
> 
> On Thu, Apr 28, 2016 at 03:16:24PM +0200, Takashi Iwai wrote:
> > On Thu, 28 Apr 2016 15:06:05 +0200,
> > Vinod Koul wrote:
> > > 
> > > From: Jeeja KP <jeeja.kp at intel.com>
> > > 
> > > After setting the stop bit of RIRB/CORB DMA, we should wait for
> > > stop bit to be set.
> > 
> > What does this actually fix?
> 
> We some some stablity issues on SKL that were attributed to DMAs not being
> quisced properly so recommendation was to to wait till DMAs are stopped

Then please write it up in the changelog.

And, did it actually improve the stability?  That's the biggest
question :)


> > > @@ -88,8 +117,8 @@ void snd_hdac_bus_stop_cmd_io(struct hdac_bus *bus)
> > >  {
> > >  	spin_lock_irq(&bus->reg_lock);
> > >  	/* disable ringbuffer DMAs */
> > > -	snd_hdac_chip_writeb(bus, RIRBCTL, 0);
> > > -	snd_hdac_chip_writeb(bus, CORBCTL, 0);
> > > +	hdac_stop_rirb_dma(bus);
> > > +	hdac_stop_corb_dma(bus);
> > 
> > Doing these one after another sequentially is a waste of time.
> > Clear two once, then sync them.
> 
> Yes agreed, that sounds better, something like adding a new wait function:
> 
> 	hdac_stop_rirb_dma(bus);
> 	hdac_stop_corb_dma(bus);
> 	hdac_wait_for_cmd_dmas(bus);

Yep, that looks better.


thanks,

Takashi