ALSA: firewire-lib: postpone to start IR context

Some devices have a quirk to postpone transmission of isoc packet for
several dozen or hundred isoc cycles since configured to transmit.
Furthermore, some devices have a quirk to transmit isoc packet with
discontinued data of its header.

In 1394 OHCI specification, software allows to start isoc context with
certain isoc cycle. Linux firewire subsystem has kernel API to use it
as well.

This commit uses the functionality of 1394 OHCI controller to handle
the quirks. At present, this feature is convenient to ALSA bebob and
fireface driver. As a result, some devices can be safely handled, as
long as I know:
 - MAudio FireWire solo
 - MAudio ProFire Lightbridge
 - MAudio FireWire 410
 - Roland FA-66
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191018061911.24909-7-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp-stream.c

@@ -9,6 +9,7 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/firewire.h>
+#include <linux/firewire-constants.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <sound/pcm.h>
@@ -983,13 +984,16 @@ static void amdtp_stream_master_first_callback(struct fw_iso_context *context,
  * @d: the AMDTP domain to which the AMDTP stream belongs
  * @is_irq_target: whether isoc context for the AMDTP stream is used to generate
  *		   hardware IRQ.
+ * @start_cycle: the isochronous cycle to start the context. Start immediately
+ *		 if negative value is given.
  *
  * The stream cannot be started until it has been configured with
  * amdtp_stream_set_parameters() and it must be started before any PCM or MIDI
  * device can be started.
  */
 static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
-			      struct amdtp_domain *d, bool is_irq_target)
+			      struct amdtp_domain *d, bool is_irq_target,
+			      int start_cycle)
 {
 	static const struct {
 		unsigned int data_block;
@@ -1146,7 +1150,7 @@ static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
 		tag |= FW_ISO_CONTEXT_MATCH_TAG0;
 
 	s->callbacked = false;
-	err = fw_iso_context_start(s->context, -1, 0, tag);
+	err = fw_iso_context_start(s->context, start_cycle, 0, tag);
 	if (err < 0)
 		goto err_pkt_descs;
 
@@ -1339,14 +1343,40 @@ 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.
  */
-int amdtp_domain_start(struct amdtp_domain *d)
+int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle)
 {
 	struct amdtp_stream *s;
-	int err = 0;
+	int cycle;
+	int err;
 
 	// Select an IT context as IRQ target.
 	list_for_each_entry(s, &d->streams, list) {
@@ -1357,17 +1387,54 @@ int amdtp_domain_start(struct amdtp_domain *d)
 		return -ENXIO;
 	d->irq_target = s;
 
+	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)
+			return err;
+
+		// 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 != d->irq_target) {
 			err = amdtp_stream_start(s, s->channel, s->speed, d,
-						 false);
+						 false, cycle_match);
 			if (err < 0)
 				goto error;
 		}
 	}
 
 	s = d->irq_target;
-	err = amdtp_stream_start(s, s->channel, s->speed, d, true);
+	err = amdtp_stream_start(s, s->channel, s->speed, d, true, -1);
 	if (err < 0)
 		goto error;
 

sound/firewire/amdtp-stream.h

@@ -288,7 +288,7 @@ void amdtp_domain_destroy(struct amdtp_domain *d);
 int amdtp_domain_add_stream(struct amdtp_domain *d, struct amdtp_stream *s,
 			    int channel, int speed);
 
-int amdtp_domain_start(struct amdtp_domain *d);
+int amdtp_domain_start(struct amdtp_domain *d, unsigned int ir_delay_cycle);
 void amdtp_domain_stop(struct amdtp_domain *d);
 
 static inline int amdtp_domain_set_events_per_period(struct amdtp_domain *d,

sound/firewire/bebob/bebob_stream.c

@@ -658,7 +658,15 @@ int snd_bebob_stream_start_duplex(struct snd_bebob *bebob)
 		if (err < 0)
 			goto error;
 
-		err = amdtp_domain_start(&bebob->domain);
+		// The device postpones start of transmission mostly for 1 sec
+		// after receives packets firstly. For safe, IR context starts
+		// 1.5 sec (=12000 cycles) later. This is within 2.0 sec
+		// (=CALLBACK_TIMEOUT).
+		// Furthermore, some devices transfer isoc packets with
+		// discontinuous counter in the beginning of packet streaming.
+		// The delay has an effect to avoid detection of this
+		// discontinuity.
+		err = amdtp_domain_start(&bebob->domain, 12000);
 		if (err < 0)
 			goto error;
 

sound/firewire/dice/dice-stream.c

@@ -462,7 +462,7 @@ int snd_dice_stream_start_duplex(struct snd_dice *dice)
 			goto error;
 		}
 
-		err = amdtp_domain_start(&dice->domain);
+		err = amdtp_domain_start(&dice->domain, 0);
 		if (err < 0)
 			goto error;
 

sound/firewire/digi00x/digi00x-stream.c

@@ -375,7 +375,7 @@ int snd_dg00x_stream_start_duplex(struct snd_dg00x *dg00x)
 		if (err < 0)
 			goto error;
 
-		err = amdtp_domain_start(&dg00x->domain);
+		err = amdtp_domain_start(&dg00x->domain, 0);
 		if (err < 0)
 			goto error;
 

sound/firewire/fireface/ff-stream.c

@@ -184,6 +184,7 @@ int snd_ff_stream_start_duplex(struct snd_ff *ff, unsigned int rate)
 	 */
 	if (!amdtp_stream_running(&ff->rx_stream)) {
 		int spd = fw_parent_device(ff->unit)->max_speed;
+		unsigned int ir_delay_cycle;
 
 		err = ff->spec->protocol->begin_session(ff, rate);
 		if (err < 0)
@@ -199,7 +200,14 @@ int snd_ff_stream_start_duplex(struct snd_ff *ff, unsigned int rate)
 		if (err < 0)
 			goto error;
 
-		err = amdtp_domain_start(&ff->domain);
+		// The device postpones start of transmission mostly for several
+		// cycles after receiving packets firstly.
+		if (ff->spec->protocol == &snd_ff_protocol_ff800)
+			ir_delay_cycle = 800;	// = 100 msec
+		else
+			ir_delay_cycle = 16;	// = 2 msec
+
+		err = amdtp_domain_start(&ff->domain, ir_delay_cycle);
 		if (err < 0)
 			goto error;
 

sound/firewire/fireworks/fireworks_stream.c

@@ -272,7 +272,7 @@ int snd_efw_stream_start_duplex(struct snd_efw *efw)
 		if (err < 0)
 			goto error;
 
-		err = amdtp_domain_start(&efw->domain);
+		err = amdtp_domain_start(&efw->domain, 0);
 		if (err < 0)
 			goto error;
 

sound/firewire/motu/motu-stream.c

@@ -260,7 +260,7 @@ int snd_motu_stream_start_duplex(struct snd_motu *motu)
 		if (err < 0)
 			goto stop_streams;
 
-		err = amdtp_domain_start(&motu->domain);
+		err = amdtp_domain_start(&motu->domain, 0);
 		if (err < 0)
 			goto stop_streams;
 

sound/firewire/oxfw/oxfw-stream.c

@@ -355,7 +355,7 @@ int snd_oxfw_stream_start_duplex(struct snd_oxfw *oxfw)
 			}
 		}
 
-		err = amdtp_domain_start(&oxfw->domain);
+		err = amdtp_domain_start(&oxfw->domain, 0);
 		if (err < 0)
 			goto error;
 

sound/firewire/tascam/tascam-stream.c

@@ -473,7 +473,7 @@ int snd_tscm_stream_start_duplex(struct snd_tscm *tscm, unsigned int rate)
 		if (err < 0)
 			goto error;
 
-		err = amdtp_domain_start(&tscm->domain);
+		err = amdtp_domain_start(&tscm->domain, 0);
 		if (err < 0)
 			return err;