[2/3] ALSA: core: modify .ack callback to take arguments for updating appl ptr
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Message ID 20170516073653.GA25195@subhransu-desktop
State New
Headers show

Commit Message

Subhransu S. Prusty May 16, 2017, 7:36 a.m. UTC
On Tue, May 16, 2017 at 07:56:44AM +0200, Takashi Iwai wrote:
> On Tue, 16 May 2017 03:01:57 +0200,
> Subhransu S. Prusty wrote:
> > 
> > From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > 
> > When appl_ptr is updated let low-level driver know, e.g.  to let the
> > low-level driver/hardware pre-fetch data opportunistically.
> > 
> > The existing .ack callback is extended with new attribute argument, to
> > support this capability. Legacy driver subscribe to SND_PCM_ACK_LEGACY and
> > doesn't process ack if it is not set. SND_PCM_ACK_APP_PTR can be used to
> > process the application ptr update in the driver like in the skylake
> > driver which can use this to inform position of appl pointer to host DMA
> > controller. The skylake driver to process the SND_PCM_ACK_APP_PTR will be
> > submitted with a separate patch set.
> > 
> > In the ALSA core, this capability is independent from the NO_REWIND
> > hardware flag. The low-level driver may however tie both options and only
> > use the updated appl_ptr when rewinds are disabled due to hardware
> > limitations.
> > 
> > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > Signed-off-by: Jaikrishna Nemallapudi <jaikrishnax.nemallapudi@intel.com>
> > Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
> 
> It might be me who suggested the extension of the ack ops, but now
> looking at the result, I reconsider whether it'd be a better choice if
> we add another ops (e.g. update_appl_ptr()) instead.  Could you try to
> rewrite the patch in that way for comparison?

Here is the version using update_appl_ptr.



Regards,
Subhransu
> 
> Besides that, the flag name SND_PCM_ACK_LEGACY sounds too ambiguous to
> me...
> 
> 
> thanks,
> 
> Takashi
> 
> > ---
> >  include/sound/pcm-indirect.h  |  4 ++--
> >  include/sound/pcm.h           |  8 +++++++-
> >  sound/core/pcm_lib.c          |  6 ++++--
> >  sound/core/pcm_native.c       | 24 +++++++++++++++++++++++-
> >  sound/mips/hal2.c             | 14 +++++++++++---
> >  sound/pci/cs46xx/cs46xx_lib.c | 18 ++++++++++++++----
> >  sound/pci/emu10k1/emupcm.c    |  8 ++++++--
> >  sound/pci/rme32.c             | 15 ++++++++++++---
> >  8 files changed, 79 insertions(+), 18 deletions(-)
> > 
> > diff --git a/include/sound/pcm-indirect.h b/include/sound/pcm-indirect.h
> > index 1df7acaaa535..2f647ff970fb 100644
> > --- a/include/sound/pcm-indirect.h
> > +++ b/include/sound/pcm-indirect.h
> > @@ -101,7 +101,7 @@ typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
> >  	if (rec->sw_io >= rec->sw_buffer_size)
> >  		rec->sw_io -= rec->sw_buffer_size;
> >  	if (substream->ops->ack)
> > -		substream->ops->ack(substream);
> > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> >  	return bytes_to_frames(substream->runtime, rec->sw_io);
> >  }
> >  
> > @@ -170,7 +170,7 @@ typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
> >  	if (rec->sw_io >= rec->sw_buffer_size)
> >  		rec->sw_io -= rec->sw_buffer_size;
> >  	if (substream->ops->ack)
> > -		substream->ops->ack(substream);
> > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> >  	return bytes_to_frames(substream->runtime, rec->sw_io);
> >  }
> >  
> > diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> > index a2682c5f5b72..0151552342f9 100644
> > --- a/include/sound/pcm.h
> > +++ b/include/sound/pcm.h
> > @@ -63,6 +63,12 @@ struct snd_pcm_hardware {
> >  struct snd_pcm_audio_tstamp_config; /* definitions further down */
> >  struct snd_pcm_audio_tstamp_report;
> >  
> > +/*
> > + * Attibute to distinguish the ack for legacy code and pointer update.
> > + */
> > +#define SND_PCM_ACK_LEGACY		BIT(0) /* Legacy callback */
> > +#define SND_PCM_ACK_APP_PTR		BIT(1) /* Update pointer callback */
> > +
> >  struct snd_pcm_ops {
> >  	int (*open)(struct snd_pcm_substream *substream);
> >  	int (*close)(struct snd_pcm_substream *substream);
> > @@ -86,7 +92,7 @@ struct snd_pcm_ops {
> >  	struct page *(*page)(struct snd_pcm_substream *substream,
> >  			     unsigned long offset);
> >  	int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);
> > -	int (*ack)(struct snd_pcm_substream *substream);
> > +	int (*ack)(struct snd_pcm_substream *substream, unsigned int ack_attr);
> >  };
> >  
> >  /*
> > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> > index 5088d4b8db22..b25af69a67da 100644
> > --- a/sound/core/pcm_lib.c
> > +++ b/sound/core/pcm_lib.c
> > @@ -2089,7 +2089,8 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
> >  			appl_ptr -= runtime->boundary;
> >  		runtime->control->appl_ptr = appl_ptr;
> >  		if (substream->ops->ack)
> > -			substream->ops->ack(substream);
> > +			substream->ops->ack(substream, SND_PCM_ACK_LEGACY |
> > +						SND_PCM_ACK_APP_PTR);
> >  
> >  		offset += frames;
> >  		size -= frames;
> > @@ -2321,7 +2322,8 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
> >  			appl_ptr -= runtime->boundary;
> >  		runtime->control->appl_ptr = appl_ptr;
> >  		if (substream->ops->ack)
> > -			substream->ops->ack(substream);
> > +			substream->ops->ack(substream, SND_PCM_ACK_LEGACY |
> > +						SND_PCM_ACK_APP_PTR);
> >  
> >  		offset += frames;
> >  		size -= frames;
> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > index 35dd4ca93f84..c14cdbd9ff86 100644
> > --- a/sound/core/pcm_native.c
> > +++ b/sound/core/pcm_native.c
> > @@ -2476,6 +2476,10 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
> >  		appl_ptr += runtime->boundary;
> >  	runtime->control->appl_ptr = appl_ptr;
> >  	ret = frames;
> > +
> > +	if (substream->ops->ack)
> > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > +
> >   __end:
> >  	snd_pcm_stream_unlock_irq(substream);
> >  	return ret;
> > @@ -2527,6 +2531,10 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr
> >  		appl_ptr += runtime->boundary;
> >  	runtime->control->appl_ptr = appl_ptr;
> >  	ret = frames;
> > +
> > +	if (substream->ops->ack)
> > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > +
> >   __end:
> >  	snd_pcm_stream_unlock_irq(substream);
> >  	return ret;
> > @@ -2576,6 +2584,10 @@ static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
> >  		appl_ptr -= runtime->boundary;
> >  	runtime->control->appl_ptr = appl_ptr;
> >  	ret = frames;
> > +
> > +	if (substream->ops->ack)
> > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > +
> >   __end:
> >  	snd_pcm_stream_unlock_irq(substream);
> >  	return ret;
> > @@ -2625,6 +2637,10 @@ static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
> >  		appl_ptr -= runtime->boundary;
> >  	runtime->control->appl_ptr = appl_ptr;
> >  	ret = frames;
> > +
> > +	if (substream->ops->ack)
> > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > +
> >   __end:
> >  	snd_pcm_stream_unlock_irq(substream);
> >  	return ret;
> > @@ -2726,8 +2742,14 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
> >  			return err;
> >  	}
> >  	snd_pcm_stream_lock_irq(substream);
> > -	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
> > +	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) {
> > +		/* boundary wrap-around is assumed to be handled in userspace */
> >  		control->appl_ptr = sync_ptr.c.control.appl_ptr;
> > +
> > +		/* let low-level driver know about appl_ptr change */
> > +		if (substream->ops->ack)
> > +			substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > +	}
> >  	else
> >  		sync_ptr.c.control.appl_ptr = control->appl_ptr;
> >  	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN))
> > diff --git a/sound/mips/hal2.c b/sound/mips/hal2.c
> > index 00fc9241d266..3740381b188a 100644
> > --- a/sound/mips/hal2.c
> > +++ b/sound/mips/hal2.c
> > @@ -577,7 +577,7 @@ static int hal2_playback_trigger(struct snd_pcm_substream *substream, int cmd)
> >  	case SNDRV_PCM_TRIGGER_START:
> >  		hal2->dac.pcm_indirect.hw_io = hal2->dac.buffer_dma;
> >  		hal2->dac.pcm_indirect.hw_data = 0;
> > -		substream->ops->ack(substream);
> > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> >  		hal2_start_dac(hal2);
> >  		break;
> >  	case SNDRV_PCM_TRIGGER_STOP:
> > @@ -610,11 +610,15 @@ static void hal2_playback_transfer(struct snd_pcm_substream *substream,
> >  
> >  }
> >  
> > -static int hal2_playback_ack(struct snd_pcm_substream *substream)
> > +static int hal2_playback_ack(struct snd_pcm_substream *substream,
> > +			     unsigned int ack_attr)
> >  {
> >  	struct snd_hal2 *hal2 = snd_pcm_substream_chip(substream);
> >  	struct hal2_codec *dac = &hal2->dac;
> >  
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	dac->pcm_indirect.hw_queue_size = H2_BUF_SIZE / 2;
> >  	snd_pcm_indirect_playback_transfer(substream,
> >  					   &dac->pcm_indirect,
> > @@ -702,11 +706,15 @@ static void hal2_capture_transfer(struct snd_pcm_substream *substream,
> >  	memcpy(substream->runtime->dma_area + rec->sw_data, buf, bytes);
> >  }
> >  
> > -static int hal2_capture_ack(struct snd_pcm_substream *substream)
> > +static int hal2_capture_ack(struct snd_pcm_substream *substream,
> > +			    unsigned int ack_attr)
> >  {
> >  	struct snd_hal2 *hal2 = snd_pcm_substream_chip(substream);
> >  	struct hal2_codec *adc = &hal2->adc;
> >  
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	snd_pcm_indirect_capture_transfer(substream,
> >  					  &adc->pcm_indirect,
> >  					  hal2_capture_transfer);
> > diff --git a/sound/pci/cs46xx/cs46xx_lib.c b/sound/pci/cs46xx/cs46xx_lib.c
> > index e4cf3187b4dd..877edda61e45 100644
> > --- a/sound/pci/cs46xx/cs46xx_lib.c
> > +++ b/sound/pci/cs46xx/cs46xx_lib.c
> > @@ -883,10 +883,15 @@ static void snd_cs46xx_pb_trans_copy(struct snd_pcm_substream *substream,
> >  	memcpy(cpcm->hw_buf.area + rec->hw_data, runtime->dma_area + rec->sw_data, bytes);
> >  }
> >  
> > -static int snd_cs46xx_playback_transfer(struct snd_pcm_substream *substream)
> > +static int snd_cs46xx_playback_transfer(struct snd_pcm_substream *substream,
> > +					unsigned int ack_attr)
> >  {
> >  	struct snd_pcm_runtime *runtime = substream->runtime;
> >  	struct snd_cs46xx_pcm * cpcm = runtime->private_data;
> > +
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	snd_pcm_indirect_playback_transfer(substream, &cpcm->pcm_rec, snd_cs46xx_pb_trans_copy);
> >  	return 0;
> >  }
> > @@ -900,9 +905,14 @@ static void snd_cs46xx_cp_trans_copy(struct snd_pcm_substream *substream,
> >  	       chip->capt.hw_buf.area + rec->hw_data, bytes);
> >  }
> >  
> > -static int snd_cs46xx_capture_transfer(struct snd_pcm_substream *substream)
> > +static int snd_cs46xx_capture_transfer(struct snd_pcm_substream *substream,
> > +					       unsigned int ack_attr)
> >  {
> >  	struct snd_cs46xx *chip = snd_pcm_substream_chip(substream);
> > +
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	snd_pcm_indirect_capture_transfer(substream, &chip->capt.pcm_rec, snd_cs46xx_cp_trans_copy);
> >  	return 0;
> >  }
> > @@ -981,11 +991,11 @@ static int snd_cs46xx_playback_trigger(struct snd_pcm_substream *substream,
> >  			cs46xx_dsp_pcm_link(chip,cpcm->pcm_channel);
> >  
> >  		if (substream->runtime->periods != CS46XX_FRAGS)
> > -			snd_cs46xx_playback_transfer(substream);
> > +			snd_cs46xx_playback_transfer(substream, SND_PCM_ACK_LEGACY);
> >  #else
> >  		spin_lock(&chip->reg_lock);
> >  		if (substream->runtime->periods != CS46XX_FRAGS)
> > -			snd_cs46xx_playback_transfer(substream);
> > +			snd_cs46xx_playback_transfer(substream, SND_PCM_ACK_LEGACY);
> >  		{ unsigned int tmp;
> >  		tmp = snd_cs46xx_peek(chip, BA1_PCTL);
> >  		tmp &= 0x0000ffff;
> > diff --git a/sound/pci/emu10k1/emupcm.c b/sound/pci/emu10k1/emupcm.c
> > index ef1cf530c929..74c78df6e5a8 100644
> > --- a/sound/pci/emu10k1/emupcm.c
> > +++ b/sound/pci/emu10k1/emupcm.c
> > @@ -1627,11 +1627,15 @@ static void fx8010_pb_trans_copy(struct snd_pcm_substream *substream,
> >  	pcm->tram_shift = tram_shift;
> >  }
> >  
> > -static int snd_emu10k1_fx8010_playback_transfer(struct snd_pcm_substream *substream)
> > +static int snd_emu10k1_fx8010_playback_transfer(struct snd_pcm_substream *substream,
> > +						unsigned int ack_attr)
> >  {
> >  	struct snd_emu10k1 *emu = snd_pcm_substream_chip(substream);
> >  	struct snd_emu10k1_fx8010_pcm *pcm = &emu->fx8010.pcm[substream->number];
> >  
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	snd_pcm_indirect_playback_transfer(substream, &pcm->pcm_rec, fx8010_pb_trans_copy);
> >  	return 0;
> >  }
> > @@ -1710,7 +1714,7 @@ static int snd_emu10k1_fx8010_playback_trigger(struct snd_pcm_substream *substre
> >  		result = snd_emu10k1_fx8010_register_irq_handler(emu, snd_emu10k1_fx8010_playback_irq, pcm->gpr_running, substream, &pcm->irq);
> >  		if (result < 0)
> >  			goto __err;
> > -		snd_emu10k1_fx8010_playback_transfer(substream);	/* roll the ball */
> > +		snd_emu10k1_fx8010_playback_transfer(substream, SND_PCM_ACK_LEGACY);	/* roll the ball */
> >  		snd_emu10k1_ptr_write(emu, emu->gpr_base + pcm->gpr_trigger, 0, 1);
> >  		break;
> >  	case SNDRV_PCM_TRIGGER_STOP:
> > diff --git a/sound/pci/rme32.c b/sound/pci/rme32.c
> > index 96d15db65dfd..3fd8de5bab26 100644
> > --- a/sound/pci/rme32.c
> > +++ b/sound/pci/rme32.c
> > @@ -1092,7 +1092,7 @@ static int snd_rme32_capture_prepare(struct snd_pcm_substream *substream)
> >  	if (cmd == SNDRV_PCM_TRIGGER_START && rme32->fullduplex_mode) {
> >  		snd_pcm_group_for_each_entry(s, substream) {
> >  			if (s == rme32->playback_substream) {
> > -				s->ops->ack(s);
> > +				s->ops->ack(s, SND_PCM_ACK_LEGACY);
> >  				break;
> >  			}
> >  		}
> > @@ -1145,11 +1145,15 @@ static void snd_rme32_pb_trans_copy(struct snd_pcm_substream *substream,
> >  		    substream->runtime->dma_area + rec->sw_data, bytes);
> >  }
> >  
> > -static int snd_rme32_playback_fd_ack(struct snd_pcm_substream *substream)
> > +static int snd_rme32_playback_fd_ack(struct snd_pcm_substream *substream,
> > +				     unsigned int ack_attr)
> >  {
> >  	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
> >  	struct snd_pcm_indirect *rec, *cprec;
> >  
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	rec = &rme32->playback_pcm;
> >  	cprec = &rme32->capture_pcm;
> >  	spin_lock(&rme32->lock);
> > @@ -1171,9 +1175,14 @@ static void snd_rme32_cp_trans_copy(struct snd_pcm_substream *substream,
> >  		      bytes);
> >  }
> >  
> > -static int snd_rme32_capture_fd_ack(struct snd_pcm_substream *substream)
> > +static int snd_rme32_capture_fd_ack(struct snd_pcm_substream *substream,
> > +					unsigned int ack_attr)
> >  {
> >  	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
> > +
> > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > +		return 0;
> > +
> >  	snd_pcm_indirect_capture_transfer(substream, &rme32->capture_pcm,
> >  					  snd_rme32_cp_trans_copy);
> >  	return 0;
> > -- 
> > 1.9.1
> > 
> _______________________________________________
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> Alsa-devel@alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel

Comments

Subhransu S. Prusty May 18, 2017, 6:18 a.m. UTC | #1
On Tue, May 16, 2017 at 01:06:57PM +0530, Subhransu S. Prusty wrote:
> On Tue, May 16, 2017 at 07:56:44AM +0200, Takashi Iwai wrote:
> > On Tue, 16 May 2017 03:01:57 +0200,
> > Subhransu S. Prusty wrote:
> > > 
> > > From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > 
> > > When appl_ptr is updated let low-level driver know, e.g.  to let the
> > > low-level driver/hardware pre-fetch data opportunistically.
> > > 
> > > The existing .ack callback is extended with new attribute argument, to
> > > support this capability. Legacy driver subscribe to SND_PCM_ACK_LEGACY and
> > > doesn't process ack if it is not set. SND_PCM_ACK_APP_PTR can be used to
> > > process the application ptr update in the driver like in the skylake
> > > driver which can use this to inform position of appl pointer to host DMA
> > > controller. The skylake driver to process the SND_PCM_ACK_APP_PTR will be
> > > submitted with a separate patch set.
> > > 
> > > In the ALSA core, this capability is independent from the NO_REWIND
> > > hardware flag. The low-level driver may however tie both options and only
> > > use the updated appl_ptr when rewinds are disabled due to hardware
> > > limitations.
> > > 
> > > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > Signed-off-by: Jaikrishna Nemallapudi <jaikrishnax.nemallapudi@intel.com>
> > > Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
> > 
> > It might be me who suggested the extension of the ack ops, but now
> > looking at the result, I reconsider whether it'd be a better choice if
> > we add another ops (e.g. update_appl_ptr()) instead.  Could you try to
> > rewrite the patch in that way for comparison?
> 
> Here is the version using update_appl_ptr.

Hi Takashi,

Did you get a chance to look at the update_appl_ptr changes?
Please let us know which one will be preferable, will submit the patches
accordingly.

Regards,
Subhransu

> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index 5344c16854d3..1accb8b522d3 100644
> --- a/include/sound/pcm.h
> +++ b/include/sound/pcm.h
> @@ -87,6 +87,7 @@ struct snd_pcm_ops {
>  			     unsigned long offset);
>  	int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);
>  	int (*ack)(struct snd_pcm_substream *substream);
> +	int (*appl_ptr_update)(struct snd_pcm_substream *substream);
>  };
>  
>  /*
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index bb1261591a1f..1656ca903c08 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -2090,6 +2090,9 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
>  		if (substream->ops->ack)
>  			substream->ops->ack(substream);
>  
> +		if (substream->ops->appl_ptr_update)
> +			substream->ops->appl_ptr_update(substream);
> +
>  		offset += frames;
>  		size -= frames;
>  		xfer += frames;
> @@ -2322,6 +2325,9 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
>  		if (substream->ops->ack)
>  			substream->ops->ack(substream);
>  
> +		if (substream->ops->appl_ptr_update)
> +			substream->ops->appl_ptr_update(substream);
> +
>  		offset += frames;
>  		size -= frames;
>  		xfer += frames;
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index be8617be12e9..c56d4ed17497 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -2475,6 +2475,10 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
>  		appl_ptr += runtime->boundary;
>  	runtime->control->appl_ptr = appl_ptr;
>  	ret = frames;
> +
> +	if (substream->ops->appl_ptr_update)
> +		substream->ops->appl_ptr_update(substream);
> +
>   __end:
>  	snd_pcm_stream_unlock_irq(substream);
>  	return ret;
> @@ -2526,6 +2530,10 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr
>  		appl_ptr += runtime->boundary;
>  	runtime->control->appl_ptr = appl_ptr;
>  	ret = frames;
> +
> +	if (substream->ops->appl_ptr_update)
> +		substream->ops->appl_ptr_update(substream);
> +
>   __end:
>  	snd_pcm_stream_unlock_irq(substream);
>  	return ret;
> @@ -2575,6 +2583,10 @@ static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
>  		appl_ptr -= runtime->boundary;
>  	runtime->control->appl_ptr = appl_ptr;
>  	ret = frames;
> +
> +	if (substream->ops->appl_ptr_update)
> +		substream->ops->appl_ptr_update(substream);
> +
>   __end:
>  	snd_pcm_stream_unlock_irq(substream);
>  	return ret;
> @@ -2624,6 +2636,10 @@ static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
>  		appl_ptr -= runtime->boundary;
>  	runtime->control->appl_ptr = appl_ptr;
>  	ret = frames;
> +
> +	if (substream->ops->appl_ptr_update)
> +		substream->ops->appl_ptr_update(substream);
> +
>   __end:
>  	snd_pcm_stream_unlock_irq(substream);
>  	return ret;
> @@ -2723,8 +2739,14 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
>  			return err;
>  	}
>  	snd_pcm_stream_lock_irq(substream);
> -	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
> +	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) {
> +		/* boundary wrap-around is assumed to be handled in userspace */
>  		control->appl_ptr = sync_ptr.c.control.appl_ptr;
> +
> +		/* let low-level driver know about appl_ptr change */
> +		if (substream->ops->appl_ptr_update)
> +			substream->ops->appl_ptr_update(substream);
> +	}
>  	else
>  		sync_ptr.c.control.appl_ptr = control->appl_ptr;
>  	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN))
> 
> 
> Regards,
> Subhransu
> > 
> > Besides that, the flag name SND_PCM_ACK_LEGACY sounds too ambiguous to
> > me...
> > 
> > 
> > thanks,
> > 
> > Takashi
> > 
> > > ---
> > >  include/sound/pcm-indirect.h  |  4 ++--
> > >  include/sound/pcm.h           |  8 +++++++-
> > >  sound/core/pcm_lib.c          |  6 ++++--
> > >  sound/core/pcm_native.c       | 24 +++++++++++++++++++++++-
> > >  sound/mips/hal2.c             | 14 +++++++++++---
> > >  sound/pci/cs46xx/cs46xx_lib.c | 18 ++++++++++++++----
> > >  sound/pci/emu10k1/emupcm.c    |  8 ++++++--
> > >  sound/pci/rme32.c             | 15 ++++++++++++---
> > >  8 files changed, 79 insertions(+), 18 deletions(-)
> > > 
> > > diff --git a/include/sound/pcm-indirect.h b/include/sound/pcm-indirect.h
> > > index 1df7acaaa535..2f647ff970fb 100644
> > > --- a/include/sound/pcm-indirect.h
> > > +++ b/include/sound/pcm-indirect.h
> > > @@ -101,7 +101,7 @@ typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
> > >  	if (rec->sw_io >= rec->sw_buffer_size)
> > >  		rec->sw_io -= rec->sw_buffer_size;
> > >  	if (substream->ops->ack)
> > > -		substream->ops->ack(substream);
> > > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> > >  	return bytes_to_frames(substream->runtime, rec->sw_io);
> > >  }
> > >  
> > > @@ -170,7 +170,7 @@ typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
> > >  	if (rec->sw_io >= rec->sw_buffer_size)
> > >  		rec->sw_io -= rec->sw_buffer_size;
> > >  	if (substream->ops->ack)
> > > -		substream->ops->ack(substream);
> > > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> > >  	return bytes_to_frames(substream->runtime, rec->sw_io);
> > >  }
> > >  
> > > diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> > > index a2682c5f5b72..0151552342f9 100644
> > > --- a/include/sound/pcm.h
> > > +++ b/include/sound/pcm.h
> > > @@ -63,6 +63,12 @@ struct snd_pcm_hardware {
> > >  struct snd_pcm_audio_tstamp_config; /* definitions further down */
> > >  struct snd_pcm_audio_tstamp_report;
> > >  
> > > +/*
> > > + * Attibute to distinguish the ack for legacy code and pointer update.
> > > + */
> > > +#define SND_PCM_ACK_LEGACY		BIT(0) /* Legacy callback */
> > > +#define SND_PCM_ACK_APP_PTR		BIT(1) /* Update pointer callback */
> > > +
> > >  struct snd_pcm_ops {
> > >  	int (*open)(struct snd_pcm_substream *substream);
> > >  	int (*close)(struct snd_pcm_substream *substream);
> > > @@ -86,7 +92,7 @@ struct snd_pcm_ops {
> > >  	struct page *(*page)(struct snd_pcm_substream *substream,
> > >  			     unsigned long offset);
> > >  	int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);
> > > -	int (*ack)(struct snd_pcm_substream *substream);
> > > +	int (*ack)(struct snd_pcm_substream *substream, unsigned int ack_attr);
> > >  };
> > >  
> > >  /*
> > > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> > > index 5088d4b8db22..b25af69a67da 100644
> > > --- a/sound/core/pcm_lib.c
> > > +++ b/sound/core/pcm_lib.c
> > > @@ -2089,7 +2089,8 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
> > >  			appl_ptr -= runtime->boundary;
> > >  		runtime->control->appl_ptr = appl_ptr;
> > >  		if (substream->ops->ack)
> > > -			substream->ops->ack(substream);
> > > +			substream->ops->ack(substream, SND_PCM_ACK_LEGACY |
> > > +						SND_PCM_ACK_APP_PTR);
> > >  
> > >  		offset += frames;
> > >  		size -= frames;
> > > @@ -2321,7 +2322,8 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
> > >  			appl_ptr -= runtime->boundary;
> > >  		runtime->control->appl_ptr = appl_ptr;
> > >  		if (substream->ops->ack)
> > > -			substream->ops->ack(substream);
> > > +			substream->ops->ack(substream, SND_PCM_ACK_LEGACY |
> > > +						SND_PCM_ACK_APP_PTR);
> > >  
> > >  		offset += frames;
> > >  		size -= frames;
> > > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > > index 35dd4ca93f84..c14cdbd9ff86 100644
> > > --- a/sound/core/pcm_native.c
> > > +++ b/sound/core/pcm_native.c
> > > @@ -2476,6 +2476,10 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
> > >  		appl_ptr += runtime->boundary;
> > >  	runtime->control->appl_ptr = appl_ptr;
> > >  	ret = frames;
> > > +
> > > +	if (substream->ops->ack)
> > > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > > +
> > >   __end:
> > >  	snd_pcm_stream_unlock_irq(substream);
> > >  	return ret;
> > > @@ -2527,6 +2531,10 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr
> > >  		appl_ptr += runtime->boundary;
> > >  	runtime->control->appl_ptr = appl_ptr;
> > >  	ret = frames;
> > > +
> > > +	if (substream->ops->ack)
> > > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > > +
> > >   __end:
> > >  	snd_pcm_stream_unlock_irq(substream);
> > >  	return ret;
> > > @@ -2576,6 +2584,10 @@ static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
> > >  		appl_ptr -= runtime->boundary;
> > >  	runtime->control->appl_ptr = appl_ptr;
> > >  	ret = frames;
> > > +
> > > +	if (substream->ops->ack)
> > > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > > +
> > >   __end:
> > >  	snd_pcm_stream_unlock_irq(substream);
> > >  	return ret;
> > > @@ -2625,6 +2637,10 @@ static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
> > >  		appl_ptr -= runtime->boundary;
> > >  	runtime->control->appl_ptr = appl_ptr;
> > >  	ret = frames;
> > > +
> > > +	if (substream->ops->ack)
> > > +		substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > > +
> > >   __end:
> > >  	snd_pcm_stream_unlock_irq(substream);
> > >  	return ret;
> > > @@ -2726,8 +2742,14 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
> > >  			return err;
> > >  	}
> > >  	snd_pcm_stream_lock_irq(substream);
> > > -	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
> > > +	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) {
> > > +		/* boundary wrap-around is assumed to be handled in userspace */
> > >  		control->appl_ptr = sync_ptr.c.control.appl_ptr;
> > > +
> > > +		/* let low-level driver know about appl_ptr change */
> > > +		if (substream->ops->ack)
> > > +			substream->ops->ack(substream, SND_PCM_ACK_APP_PTR);
> > > +	}
> > >  	else
> > >  		sync_ptr.c.control.appl_ptr = control->appl_ptr;
> > >  	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN))
> > > diff --git a/sound/mips/hal2.c b/sound/mips/hal2.c
> > > index 00fc9241d266..3740381b188a 100644
> > > --- a/sound/mips/hal2.c
> > > +++ b/sound/mips/hal2.c
> > > @@ -577,7 +577,7 @@ static int hal2_playback_trigger(struct snd_pcm_substream *substream, int cmd)
> > >  	case SNDRV_PCM_TRIGGER_START:
> > >  		hal2->dac.pcm_indirect.hw_io = hal2->dac.buffer_dma;
> > >  		hal2->dac.pcm_indirect.hw_data = 0;
> > > -		substream->ops->ack(substream);
> > > +		substream->ops->ack(substream, SND_PCM_ACK_LEGACY);
> > >  		hal2_start_dac(hal2);
> > >  		break;
> > >  	case SNDRV_PCM_TRIGGER_STOP:
> > > @@ -610,11 +610,15 @@ static void hal2_playback_transfer(struct snd_pcm_substream *substream,
> > >  
> > >  }
> > >  
> > > -static int hal2_playback_ack(struct snd_pcm_substream *substream)
> > > +static int hal2_playback_ack(struct snd_pcm_substream *substream,
> > > +			     unsigned int ack_attr)
> > >  {
> > >  	struct snd_hal2 *hal2 = snd_pcm_substream_chip(substream);
> > >  	struct hal2_codec *dac = &hal2->dac;
> > >  
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	dac->pcm_indirect.hw_queue_size = H2_BUF_SIZE / 2;
> > >  	snd_pcm_indirect_playback_transfer(substream,
> > >  					   &dac->pcm_indirect,
> > > @@ -702,11 +706,15 @@ static void hal2_capture_transfer(struct snd_pcm_substream *substream,
> > >  	memcpy(substream->runtime->dma_area + rec->sw_data, buf, bytes);
> > >  }
> > >  
> > > -static int hal2_capture_ack(struct snd_pcm_substream *substream)
> > > +static int hal2_capture_ack(struct snd_pcm_substream *substream,
> > > +			    unsigned int ack_attr)
> > >  {
> > >  	struct snd_hal2 *hal2 = snd_pcm_substream_chip(substream);
> > >  	struct hal2_codec *adc = &hal2->adc;
> > >  
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	snd_pcm_indirect_capture_transfer(substream,
> > >  					  &adc->pcm_indirect,
> > >  					  hal2_capture_transfer);
> > > diff --git a/sound/pci/cs46xx/cs46xx_lib.c b/sound/pci/cs46xx/cs46xx_lib.c
> > > index e4cf3187b4dd..877edda61e45 100644
> > > --- a/sound/pci/cs46xx/cs46xx_lib.c
> > > +++ b/sound/pci/cs46xx/cs46xx_lib.c
> > > @@ -883,10 +883,15 @@ static void snd_cs46xx_pb_trans_copy(struct snd_pcm_substream *substream,
> > >  	memcpy(cpcm->hw_buf.area + rec->hw_data, runtime->dma_area + rec->sw_data, bytes);
> > >  }
> > >  
> > > -static int snd_cs46xx_playback_transfer(struct snd_pcm_substream *substream)
> > > +static int snd_cs46xx_playback_transfer(struct snd_pcm_substream *substream,
> > > +					unsigned int ack_attr)
> > >  {
> > >  	struct snd_pcm_runtime *runtime = substream->runtime;
> > >  	struct snd_cs46xx_pcm * cpcm = runtime->private_data;
> > > +
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	snd_pcm_indirect_playback_transfer(substream, &cpcm->pcm_rec, snd_cs46xx_pb_trans_copy);
> > >  	return 0;
> > >  }
> > > @@ -900,9 +905,14 @@ static void snd_cs46xx_cp_trans_copy(struct snd_pcm_substream *substream,
> > >  	       chip->capt.hw_buf.area + rec->hw_data, bytes);
> > >  }
> > >  
> > > -static int snd_cs46xx_capture_transfer(struct snd_pcm_substream *substream)
> > > +static int snd_cs46xx_capture_transfer(struct snd_pcm_substream *substream,
> > > +					       unsigned int ack_attr)
> > >  {
> > >  	struct snd_cs46xx *chip = snd_pcm_substream_chip(substream);
> > > +
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	snd_pcm_indirect_capture_transfer(substream, &chip->capt.pcm_rec, snd_cs46xx_cp_trans_copy);
> > >  	return 0;
> > >  }
> > > @@ -981,11 +991,11 @@ static int snd_cs46xx_playback_trigger(struct snd_pcm_substream *substream,
> > >  			cs46xx_dsp_pcm_link(chip,cpcm->pcm_channel);
> > >  
> > >  		if (substream->runtime->periods != CS46XX_FRAGS)
> > > -			snd_cs46xx_playback_transfer(substream);
> > > +			snd_cs46xx_playback_transfer(substream, SND_PCM_ACK_LEGACY);
> > >  #else
> > >  		spin_lock(&chip->reg_lock);
> > >  		if (substream->runtime->periods != CS46XX_FRAGS)
> > > -			snd_cs46xx_playback_transfer(substream);
> > > +			snd_cs46xx_playback_transfer(substream, SND_PCM_ACK_LEGACY);
> > >  		{ unsigned int tmp;
> > >  		tmp = snd_cs46xx_peek(chip, BA1_PCTL);
> > >  		tmp &= 0x0000ffff;
> > > diff --git a/sound/pci/emu10k1/emupcm.c b/sound/pci/emu10k1/emupcm.c
> > > index ef1cf530c929..74c78df6e5a8 100644
> > > --- a/sound/pci/emu10k1/emupcm.c
> > > +++ b/sound/pci/emu10k1/emupcm.c
> > > @@ -1627,11 +1627,15 @@ static void fx8010_pb_trans_copy(struct snd_pcm_substream *substream,
> > >  	pcm->tram_shift = tram_shift;
> > >  }
> > >  
> > > -static int snd_emu10k1_fx8010_playback_transfer(struct snd_pcm_substream *substream)
> > > +static int snd_emu10k1_fx8010_playback_transfer(struct snd_pcm_substream *substream,
> > > +						unsigned int ack_attr)
> > >  {
> > >  	struct snd_emu10k1 *emu = snd_pcm_substream_chip(substream);
> > >  	struct snd_emu10k1_fx8010_pcm *pcm = &emu->fx8010.pcm[substream->number];
> > >  
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	snd_pcm_indirect_playback_transfer(substream, &pcm->pcm_rec, fx8010_pb_trans_copy);
> > >  	return 0;
> > >  }
> > > @@ -1710,7 +1714,7 @@ static int snd_emu10k1_fx8010_playback_trigger(struct snd_pcm_substream *substre
> > >  		result = snd_emu10k1_fx8010_register_irq_handler(emu, snd_emu10k1_fx8010_playback_irq, pcm->gpr_running, substream, &pcm->irq);
> > >  		if (result < 0)
> > >  			goto __err;
> > > -		snd_emu10k1_fx8010_playback_transfer(substream);	/* roll the ball */
> > > +		snd_emu10k1_fx8010_playback_transfer(substream, SND_PCM_ACK_LEGACY);	/* roll the ball */
> > >  		snd_emu10k1_ptr_write(emu, emu->gpr_base + pcm->gpr_trigger, 0, 1);
> > >  		break;
> > >  	case SNDRV_PCM_TRIGGER_STOP:
> > > diff --git a/sound/pci/rme32.c b/sound/pci/rme32.c
> > > index 96d15db65dfd..3fd8de5bab26 100644
> > > --- a/sound/pci/rme32.c
> > > +++ b/sound/pci/rme32.c
> > > @@ -1092,7 +1092,7 @@ static int snd_rme32_capture_prepare(struct snd_pcm_substream *substream)
> > >  	if (cmd == SNDRV_PCM_TRIGGER_START && rme32->fullduplex_mode) {
> > >  		snd_pcm_group_for_each_entry(s, substream) {
> > >  			if (s == rme32->playback_substream) {
> > > -				s->ops->ack(s);
> > > +				s->ops->ack(s, SND_PCM_ACK_LEGACY);
> > >  				break;
> > >  			}
> > >  		}
> > > @@ -1145,11 +1145,15 @@ static void snd_rme32_pb_trans_copy(struct snd_pcm_substream *substream,
> > >  		    substream->runtime->dma_area + rec->sw_data, bytes);
> > >  }
> > >  
> > > -static int snd_rme32_playback_fd_ack(struct snd_pcm_substream *substream)
> > > +static int snd_rme32_playback_fd_ack(struct snd_pcm_substream *substream,
> > > +				     unsigned int ack_attr)
> > >  {
> > >  	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
> > >  	struct snd_pcm_indirect *rec, *cprec;
> > >  
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	rec = &rme32->playback_pcm;
> > >  	cprec = &rme32->capture_pcm;
> > >  	spin_lock(&rme32->lock);
> > > @@ -1171,9 +1175,14 @@ static void snd_rme32_cp_trans_copy(struct snd_pcm_substream *substream,
> > >  		      bytes);
> > >  }
> > >  
> > > -static int snd_rme32_capture_fd_ack(struct snd_pcm_substream *substream)
> > > +static int snd_rme32_capture_fd_ack(struct snd_pcm_substream *substream,
> > > +					unsigned int ack_attr)
> > >  {
> > >  	struct rme32 *rme32 = snd_pcm_substream_chip(substream);
> > > +
> > > +	if (!(ack_attr & SND_PCM_ACK_LEGACY))
> > > +		return 0;
> > > +
> > >  	snd_pcm_indirect_capture_transfer(substream, &rme32->capture_pcm,
> > >  					  snd_rme32_cp_trans_copy);
> > >  	return 0;
> > > -- 
> > > 1.9.1
> > > 
> > _______________________________________________
> > Alsa-devel mailing list
> > Alsa-devel@alsa-project.org
> > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
> 
> --
Takashi Iwai May 18, 2017, 8:09 a.m. UTC | #2
On Thu, 18 May 2017 08:18:21 +0200,
Subhransu S. Prusty wrote:
> 
> On Tue, May 16, 2017 at 01:06:57PM +0530, Subhransu S. Prusty wrote:
> > On Tue, May 16, 2017 at 07:56:44AM +0200, Takashi Iwai wrote:
> > > On Tue, 16 May 2017 03:01:57 +0200,
> > > Subhransu S. Prusty wrote:
> > > > 
> > > > From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > > 
> > > > When appl_ptr is updated let low-level driver know, e.g.  to let the
> > > > low-level driver/hardware pre-fetch data opportunistically.
> > > > 
> > > > The existing .ack callback is extended with new attribute argument, to
> > > > support this capability. Legacy driver subscribe to SND_PCM_ACK_LEGACY and
> > > > doesn't process ack if it is not set. SND_PCM_ACK_APP_PTR can be used to
> > > > process the application ptr update in the driver like in the skylake
> > > > driver which can use this to inform position of appl pointer to host DMA
> > > > controller. The skylake driver to process the SND_PCM_ACK_APP_PTR will be
> > > > submitted with a separate patch set.
> > > > 
> > > > In the ALSA core, this capability is independent from the NO_REWIND
> > > > hardware flag. The low-level driver may however tie both options and only
> > > > use the updated appl_ptr when rewinds are disabled due to hardware
> > > > limitations.
> > > > 
> > > > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > > Signed-off-by: Jaikrishna Nemallapudi <jaikrishnax.nemallapudi@intel.com>
> > > > Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
> > > 
> > > It might be me who suggested the extension of the ack ops, but now
> > > looking at the result, I reconsider whether it'd be a better choice if
> > > we add another ops (e.g. update_appl_ptr()) instead.  Could you try to
> > > rewrite the patch in that way for comparison?
> > 
> > Here is the version using update_appl_ptr.
> 
> Hi Takashi,
> 
> Did you get a chance to look at the update_appl_ptr changes?
> Please let us know which one will be preferable, will submit the patches
> accordingly.

Now I have a mixed feeling.  Using ack() is basically "the right
thing".  The update of appl_ptr in forward/rewind and sync_ptr should
be notified to ack() in general.  It's the purpose of ack(), after
all.  In that sense, we may call ack() without any argument from any
places.

The only problem is that the rewind is broken on some drivers, and
calling ack() may lead to unexpected results.

That is, we should look at these existing drivers and handle the
rewind case (negative appl_ptr diff) appropriately -- or maybe we
should add a flag to disallow the rewind on such drivers.
After that, ack() can be called safely from all places that update
appl_ptr.

... this is one way.  Another way is to allow a quick hack and doubly
call a new callback.

I prefer the former, but obviously it'll take longer.  So it depends
on urgency.


Takashi
Vinod Koul May 22, 2017, 5:41 a.m. UTC | #3
On Thu, May 18, 2017 at 10:09:23AM +0200, Takashi Iwai wrote:
> On Thu, 18 May 2017 08:18:21 +0200,
> Subhransu S. Prusty wrote:
> > 
> > On Tue, May 16, 2017 at 01:06:57PM +0530, Subhransu S. Prusty wrote:
> > > On Tue, May 16, 2017 at 07:56:44AM +0200, Takashi Iwai wrote:
> > > > On Tue, 16 May 2017 03:01:57 +0200,
> > > > Subhransu S. Prusty wrote:
> > > > > 
> > > > > From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > > > 
> > > > > When appl_ptr is updated let low-level driver know, e.g.  to let the
> > > > > low-level driver/hardware pre-fetch data opportunistically.
> > > > > 
> > > > > The existing .ack callback is extended with new attribute argument, to
> > > > > support this capability. Legacy driver subscribe to SND_PCM_ACK_LEGACY and
> > > > > doesn't process ack if it is not set. SND_PCM_ACK_APP_PTR can be used to
> > > > > process the application ptr update in the driver like in the skylake
> > > > > driver which can use this to inform position of appl pointer to host DMA
> > > > > controller. The skylake driver to process the SND_PCM_ACK_APP_PTR will be
> > > > > submitted with a separate patch set.
> > > > > 
> > > > > In the ALSA core, this capability is independent from the NO_REWIND
> > > > > hardware flag. The low-level driver may however tie both options and only
> > > > > use the updated appl_ptr when rewinds are disabled due to hardware
> > > > > limitations.
> > > > > 
> > > > > Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> > > > > Signed-off-by: Jaikrishna Nemallapudi <jaikrishnax.nemallapudi@intel.com>
> > > > > Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
> > > > 
> > > > It might be me who suggested the extension of the ack ops, but now
> > > > looking at the result, I reconsider whether it'd be a better choice if
> > > > we add another ops (e.g. update_appl_ptr()) instead.  Could you try to
> > > > rewrite the patch in that way for comparison?
> > > 
> > > Here is the version using update_appl_ptr.
> > 
> > Hi Takashi,
> > 
> > Did you get a chance to look at the update_appl_ptr changes?
> > Please let us know which one will be preferable, will submit the patches
> > accordingly.
> 
> Now I have a mixed feeling.  Using ack() is basically "the right
> thing".  The update of appl_ptr in forward/rewind and sync_ptr should
> be notified to ack() in general.  It's the purpose of ack(), after
> all.  In that sense, we may call ack() without any argument from any
> places.
> 
> The only problem is that the rewind is broken on some drivers, and
> calling ack() may lead to unexpected results.

Precisely the reason we went with an arg to make it opt-in and ensure
existing drivers don't break

> That is, we should look at these existing drivers and handle the
> rewind case (negative appl_ptr diff) appropriately -- or maybe we
> should add a flag to disallow the rewind on such drivers.
> After that, ack() can be called safely from all places that update
> appl_ptr.

Testing a large set of those drivers will be an issue :(

> ... this is one way.  Another way is to allow a quick hack and doubly
> call a new callback.

Sorry but how would invoking twice help here?

> 
> I prefer the former, but obviously it'll take longer.  So it depends
> on urgency.

We have been going back and forth on this for at least couple of years now,
so I would really love this to get merged before next window :)

Patch
diff mbox

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 5344c16854d3..1accb8b522d3 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -87,6 +87,7 @@  struct snd_pcm_ops {
 			     unsigned long offset);
 	int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);
 	int (*ack)(struct snd_pcm_substream *substream);
+	int (*appl_ptr_update)(struct snd_pcm_substream *substream);
 };
 
 /*
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index bb1261591a1f..1656ca903c08 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2090,6 +2090,9 @@  static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
 		if (substream->ops->ack)
 			substream->ops->ack(substream);
 
+		if (substream->ops->appl_ptr_update)
+			substream->ops->appl_ptr_update(substream);
+
 		offset += frames;
 		size -= frames;
 		xfer += frames;
@@ -2322,6 +2325,9 @@  static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
 		if (substream->ops->ack)
 			substream->ops->ack(substream);
 
+		if (substream->ops->appl_ptr_update)
+			substream->ops->appl_ptr_update(substream);
+
 		offset += frames;
 		size -= frames;
 		xfer += frames;
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index be8617be12e9..c56d4ed17497 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -2475,6 +2475,10 @@  static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
 		appl_ptr += runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (substream->ops->appl_ptr_update)
+		substream->ops->appl_ptr_update(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2526,6 +2530,10 @@  static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr
 		appl_ptr += runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (substream->ops->appl_ptr_update)
+		substream->ops->appl_ptr_update(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2575,6 +2583,10 @@  static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
 		appl_ptr -= runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (substream->ops->appl_ptr_update)
+		substream->ops->appl_ptr_update(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2624,6 +2636,10 @@  static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
 		appl_ptr -= runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (substream->ops->appl_ptr_update)
+		substream->ops->appl_ptr_update(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2723,8 +2739,14 @@  static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
 			return err;
 	}
 	snd_pcm_stream_lock_irq(substream);
-	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
+	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) {
+		/* boundary wrap-around is assumed to be handled in userspace */
 		control->appl_ptr = sync_ptr.c.control.appl_ptr;
+
+		/* let low-level driver know about appl_ptr change */
+		if (substream->ops->appl_ptr_update)
+			substream->ops->appl_ptr_update(substream);
+	}
 	else
 		sync_ptr.c.control.appl_ptr = control->appl_ptr;
 	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN))