[alsa-devel] [PATCH 1/1] audio: Fix playback noise with 24/32 bit sample size on BXT

[Lu, Han]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Monday, December 7, 2015 2:57 PM
> To: Lu, Han
> Cc: libin.yang at linux.intel.com; mengdong.lin at linux.intel.com;
> han.lu at linux.intel.com; alsa-devel at alsa-project.org
> Subject: Re: [PATCH 1/1] audio: Fix playback noise with 24/32 bit sample size
> on BXT
> 
> On Mon, 07 Dec 2015 03:51:49 +0100,
> han.lu at intel.com wrote:
> >
> > From: "Lu, Han" <han.lu at intel.com>
> >
> > In BXT-P A0, HD-Audio DMA requests is later than expected, and makes
> > an audio stream sensitive to system latencies when
> > 24/32 bits are playing.
> > Adjusting threshold of DMA fifo to force the DMA request sooner to
> > improve latency tolerance at the expense of power.
> >
> > Signed-off-by: Lu, Han <han.lu at intel.com>
> 
> It's a wrong place to patch.  hda_controller.c is for generic HD-audio.  The
> Intel-specific code should go into hda_intel.c.
> 

Sorry. I submitted patch V2, please review, Thanks.

BR,
Han

> 
> thanks,
> 
> Takashi
> 
> >
> > diff --git a/include/sound/hda_register.h
> > b/include/sound/hda_register.h index 2ae8812..94dc6a9 100644
> > --- a/include/sound/hda_register.h
> > +++ b/include/sound/hda_register.h
> > @@ -93,6 +93,9 @@ enum { SDI0, SDI1, SDI2, SDI3, SDO0, SDO1, SDO2,
> SDO3 };
> >  #define AZX_REG_HSW_EM4			0x100c
> >  #define AZX_REG_HSW_EM5			0x1010
> >
> > +/* Skylake/Broxton display HD-A controller Extended Mode registers */
> > +#define AZX_REG_SKL_EM4L		0x1040
> > +
> >  /* PCI space */
> >  #define AZX_PCIREG_TCSEL		0x44
> >
> > diff --git a/sound/pci/hda/hda_controller.c
> > b/sound/pci/hda/hda_controller.c index 22dbfa5..6c2aa4c 100644
> > --- a/sound/pci/hda/hda_controller.c
> > +++ b/sound/pci/hda/hda_controller.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/module.h>
> >  #include <linux/pm_runtime.h>
> >  #include <linux/slab.h>
> > +#include <linux/pci.h>
> >  #include <sound/core.h>
> >  #include <sound/initval.h>
> >  #include "hda_controller.h"
> > @@ -34,6 +35,8 @@
> >  #define CREATE_TRACE_POINTS
> >  #include "hda_controller_trace.h"
> >
> > +#define is_broxton(pci)	((pci)->device == 0x5a98)
> > +
> >  /* DSP lock helpers */
> >  #define dsp_lock(dev)		snd_hdac_dsp_lock(azx_stream(dev))
> >  #define dsp_unlock(dev)
> 	snd_hdac_dsp_unlock(azx_stream(dev))
> > @@ -880,14 +883,35 @@
> > EXPORT_SYMBOL_GPL(snd_hda_codec_load_dsp_cleanup);
> >  #endif /* CONFIG_SND_HDA_DSP_LOADER */
> >
> >  /*
> > + * In BXT-P A0, HD-Audio DMA requests is later than expected,
> > + * and makes an audio stream sensitive to system latencies when
> > + * 24/32 bits are playing.
> > + * Adjusting threshold of DMA fifo to force the DMA request
> > + * sooner to improve latency tolerance at the expense of power.
> > + */
> > +static void bxt_reduce_dma_latency(struct azx *chip) {
> > +	u32 val;
> > +
> > +	val = azx_readl(chip, SKL_EM4L);
> > +	val &= (0x3 << 20);
> > +	azx_writel(chip, SKL_EM4L, val);
> > +}
> > +
> > +/*
> >   * reset and start the controller registers
> >   */
> >  void azx_init_chip(struct azx *chip, bool full_reset)  {
> > +	struct pci_dev *pci = chip->pci;
> > +
> >  	if (snd_hdac_bus_init_chip(azx_bus(chip), full_reset)) {
> >  		/* correct RINTCNT for CXT */
> >  		if (chip->driver_caps & AZX_DCAPS_CTX_WORKAROUND)
> >  			azx_writew(chip, RINTCNT, 0xc0);
> > +		/* reduce dma latency to avoid noise */
> > +		if (is_broxton(pci))
> > +			bxt_reduce_dma_latency(chip);
> >  	}
> >  }
> >  EXPORT_SYMBOL_GPL(azx_init_chip);
> > --
> > 2.5.0
> >