ALSA: firewire-lib: skip initial packets instead of scheduling IR context

Current implementation of ALSA IEC 61883-1/6 packet streaming engine
allows drivers to decide isochronous cycle to start IR context. This
option is mainly used to avoid processing the sequence of packet with
some quirks; e.g. discontinuity of counter. However, it's inconvenient
to fail to continue packet processing when the target device doesn't
start transmission of packet till the decided cycle.

This commit changes the behaviour. As an alternative to the start cycle
for IR context, the cycle count to drop content of packet in the beginning
of IR context.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210520040154.80450-6-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 13 insertions, 67 deletions

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index 35925c9666fc..48ed9612407f 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -1199,12 +1199,16 @@ static void amdtp_stream_first_callback(struct fw_iso_context *context,
 		}
 
 		if (stream_count == callbacked_count) {
+			unsigned int next_cycle;
+
 			list_for_each_entry(s, &d->streams, list) {
 				if (s->direction != AMDTP_IN_STREAM)
 					continue;
 
-				if (compare_ohci_cycle_count(s->next_cycle, cycle) > 0)
-					cycle = s->next_cycle;
+				next_cycle = increment_ohci_cycle_count(s->next_cycle,
+								d->processing_cycle.tx_init_skip);
+				if (compare_ohci_cycle_count(next_cycle, cycle) > 0)
+					cycle = next_cycle;
 
 				s->context->callback.sc = process_tx_packets_intermediately;
 			}
@@ -1533,36 +1537,13 @@ int amdtp_domain_add_stream(struct amdtp_domain *d, struct amdtp_stream *s,
 }
 EXPORT_SYMBOL_GPL(amdtp_domain_add_stream);
 
-static int get_current_cycle_time(struct fw_card *fw_card, int *cur_cycle)
-{
-	int generation;
-	int rcode;
-	__be32 reg;
-	u32 data;
-
-	// This is a request to local 1394 OHCI controller and expected to
-	// complete without any event waiting.
-	generation = fw_card->generation;
-	smp_rmb();	// node_id vs. generation.
-	rcode = fw_run_transaction(fw_card, TCODE_READ_QUADLET_REQUEST,
-				   fw_card->node_id, generation, SCODE_100,
-				   CSR_REGISTER_BASE + CSR_CYCLE_TIME,
-				   &reg, sizeof(reg));
-	if (rcode != RCODE_COMPLETE)
-		return -EIO;
-
-	data = be32_to_cpu(reg);
-	*cur_cycle = data >> 12;
-
-	return 0;
-}
-
 /**
  * amdtp_domain_start - start sending packets for isoc context in the domain.
  * @d: the AMDTP domain.
- * @ir_delay_cycle: the cycle delay to start all IR contexts.
+ * @tx_init_skip_cycles: the number of cycles to skip processing packets at initial stage of IR
+ *			 contexts.
  */
-int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
+int amdtp_domain_start(struct amdtp_domain *d, unsigned int tx_init_skip_cycles)
 {
 	static const struct {
 		unsigned int data_block;
@@ -1581,7 +1562,6 @@ int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
 	unsigned int idle_irq_interval;
 	unsigned int queue_size;
 	struct amdtp_stream *s;
-	int cycle;
 	int err;
 
 	// Select an IT context as IRQ target.
@@ -1593,6 +1573,8 @@ int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
 		return -ENXIO;
 	d->irq_target = s;
 
+	d->processing_cycle.tx_init_skip = tx_init_skip_cycles;
+
 	// This is a case that AMDTP streams in domain run just for MIDI
 	// substream. Use the number of events equivalent to 10 msec as
 	// interval of hardware IRQ.
@@ -1615,48 +1597,12 @@ int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
 	d->syt_offset_state = entry->syt_offset;
 	d->last_syt_offset = TICKS_PER_CYCLE;
 
-	if (ir_delay_cycle > 0) {
-		struct fw_card *fw_card = fw_parent_device(s->unit)->card;
-
-		err = get_current_cycle_time(fw_card, &cycle);
-		if (err < 0)
-			goto error;
-
-		// No need to care overflow in cycle field because of enough
-		// width.
-		cycle += ir_delay_cycle;
-
-		// Round up to sec field.
-		if ((cycle & 0x00001fff) >= CYCLES_PER_SECOND) {
-			unsigned int sec;
-
-			// The sec field can overflow.
-			sec = (cycle & 0xffffe000) >> 13;
-			cycle = (++sec << 13) |
-				((cycle & 0x00001fff) / CYCLES_PER_SECOND);
-		}
-
-		// In OHCI 1394 specification, lower 2 bits are available for
-		// sec field.
-		cycle &= 0x00007fff;
-	} else {
-		cycle = -1;
-	}
-
 	list_for_each_entry(s, &d->streams, list) {
-		int cycle_match;
-
-		if (s->direction == AMDTP_IN_STREAM) {
-			cycle_match = cycle;
-		} else {
-			// IT context starts immediately.
-			cycle_match = -1;
+		if (s->direction == AMDTP_OUT_STREAM)
 			s->ctx_data.rx.seq_index = 0;
-		}
 
 		if (s != d->irq_target) {
-			err = amdtp_stream_start(s, s->channel, s->speed,
-						 cycle_match, queue_size, 0);
+			err = amdtp_stream_start(s, s->channel, s->speed, -1, queue_size, 0);
 			if (err < 0)
 				goto error;
 		}