Commit d360870a authored by Takashi Sakamoto's avatar Takashi Sakamoto Committed by Takashi Iwai
Browse files

ALSA: firewire-lib: support NO_PERIOD_WAKEUP in ALSA PCM runtime 

Drivers of ALSA firewire stack can process packets for IT/IR context in
process context when the process operates ALSA PCM character device by
calling ioctl(2) with some requests. The ioctl requests are:

 * SNDRV_PCM_IOCTL_HWSYNC
 * SNDRV_PCM_IOCTL_SYNC_PTR
 * SNDRV_PCM_IOCTL_REWIND
 * SNDRV_PCM_IOCTL_FORWARD
 * SNDRV_PCM_IOCTL_WRITEI_FRAMES
 * SNDRV_PCM_IOCTL_READI_FRAMES
 * SNDRV_PCM_IOCTL_WRITEN_FRAMES
 * SNDRV_PCM_IOCTL_READN_FRAMES

This means that general application can process PCM frames apart from
hardware IRQ invocation, even if they are programmed by either IRQ-based
scheduling model or Timer-based scheduling model.

This commit add support for Timer-based scheduling model by allowing
PCM runtime to suppress both process wakeup per period and scheduling
hardware IRQ.

SNDRV_PCM_INFO_BATCH is obsoleted since ALSA IEC 61883-1/6 packet streaming
engine can report the number of transferred PCM frames within PCM period
boundary. The granularity equals to SYT_INTERVAL in blocking transmission.
In non-blocking transmission, it doesn't equal to SYT_INTERVAL but doesn't
exceed.

This patch is tested with PulseAudio, and --sched-model option of axfer
with fix against the issue reported at:

 * https://lore.kernel.org/alsa-devel/687f9871-7484-1370-04d1-9c968e86f72b@linux.intel.com/#r



Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210527123253.174315-1-o-takashi@sakamocchi.jp


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 2f21a177

sound/firewire/amdtp-stream.c

+21 −6
Original line number Diff line number Diff line
@@ -192,14 +192,13 @@ int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s, 
	unsigned int maximum_usec_per_period;

	int err;



	hw->info = SNDRV_PCM_INFO_BATCH |

		   SNDRV_PCM_INFO_BLOCK_TRANSFER |

	hw->info = SNDRV_PCM_INFO_BLOCK_TRANSFER |

		   SNDRV_PCM_INFO_INTERLEAVED |

		   SNDRV_PCM_INFO_JOINT_DUPLEX |

		   SNDRV_PCM_INFO_MMAP |

		   SNDRV_PCM_INFO_MMAP_VALID;

		   SNDRV_PCM_INFO_MMAP_VALID |

		   SNDRV_PCM_INFO_NO_PERIOD_WAKEUP;



	/* SNDRV_PCM_INFO_BATCH */

	hw->periods_min = 2;

	hw->periods_max = UINT_MAX;
@@ -610,6 +609,11 @@ static void update_pcm_pointers(struct amdtp_stream *s, 
	s->pcm_period_pointer += frames;

	if (s->pcm_period_pointer >= pcm->runtime->period_size) {

		s->pcm_period_pointer -= pcm->runtime->period_size;



		// The program in user process should periodically check the status of intermediate

		// buffer associated to PCM substream to process PCM frames in the buffer, instead

		// of receiving notification of period elapsed by poll wait.

		if (!pcm->runtime->no_period_wakeup)

			queue_work(system_highpri_wq, &s->period_work);

	}

}
@@ -1056,6 +1060,7 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_ 
	unsigned int event_count = s->ctx_data.rx.event_count;

	unsigned int pkt_header_length;

	unsigned int packets;

	bool need_hw_irq;

	int i;



	if (s->packet_index < 0)
@@ -1075,6 +1080,16 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_ 
	else

		pkt_header_length = 0;



	if (s == d->irq_target) {

		// At NO_PERIOD_WAKEUP mode, the packets for all IT/IR contexts are processed by

		// the tasks of user process operating ALSA PCM character device by calling ioctl(2)

		// with some requests, instead of scheduled hardware IRQ of an IT context.

		struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);

		need_hw_irq = !pcm || !pcm->runtime->no_period_wakeup;

	} else {

		need_hw_irq = false;

	}



	for (i = 0; i < packets; ++i) {

		const struct pkt_desc *desc = s->pkt_descs + i;

		struct {
@@ -1091,7 +1106,7 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_ 
			event_count += desc->data_blocks;

			if (event_count >= events_per_period) {

				event_count -= events_per_period;

				sched_irq = true;

				sched_irq = need_hw_irq;

			}

		}