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@linu...

Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- sound/firewire/amdtp-stream.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c index 68ffbc33f692..8e72e7f4c082 100644 --- a/sound/firewire/amdtp-stream.c +++ b/sound/firewire/amdtp-stream.c @@ -191,14 +191,13 @@ 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;

@@ -503,7 +502,12 @@ 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; - queue_work(system_highpri_wq, &s->period_work); + + // 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); } }

@@ -949,6 +953,7 @@ 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) @@ -968,6 +973,16 @@ 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 { @@ -984,7 +999,7 @@ 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; } }