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

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Hi,

On May 16 2017 10:01, Subhransu S. Prusty wrote:

From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: Jaikrishna Nemallapudi <jaikrishnax.nemallapudi@xxxxxxxxx>
Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@xxxxxxxxx>
---
  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
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