Re: [PATCH 2/3] ALSA: core: modify .ack callback to take arguments for updating appl ptr

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi,

On May 16 2017 10:01, 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>
> ---
>   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(-)

I think it better to take care of 
'drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c' as well. 
This is a driver for sound functionality of Raspberry PI 1/zero and some 
people may still get influences from this work.

$ git grep -A20 'struct snd_pcm_ops' v4.12-rc1 | grep \\.ack
v4.12-rc1:drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c-...
...

> 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;

Regards

Takashi Sakamoto