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

[Vinod Koul]

On Thu, Apr 28, 2016 at 03:53:16PM +0200, Takashi Iwai wrote:
> 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.

Sure thing

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

Yes it did :)

> > > > @@ -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.

Okay will update and post v2

-- 
~Vinod