ALSA: firewire-lib: use circular linked list to enumerate packet descriptors

Current implementation uses list of packet descriptor as template to
schedule isochronous packet. The packet descriptors are operated by
position and size, while circular linked list is convenient to enumerate
the packet descriptors.

This commit utilizes circular linked list for the purpose.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230109021738.75543-2-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp-stream.c

@@ -504,7 +504,7 @@ static unsigned int calculate_cached_cycle_count(struct amdtp_stream *s, unsigne
 	return cycles;
 }
 
-static void cache_seq(struct amdtp_stream *s, const struct pkt_desc *descs, unsigned int desc_count)
+static void cache_seq(struct amdtp_stream *s, const struct pkt_desc *src, unsigned int desc_count)
 {
 	const unsigned int transfer_delay = s->transfer_delay;
 	const unsigned int cache_size = s->ctx_data.tx.cache.size;
@@ -515,7 +515,6 @@ static void cache_seq(struct amdtp_stream *s, const struct pkt_desc *descs, unsi
 
 	for (i = 0; i < desc_count; ++i) {
 		struct seq_desc *dst = cache + cache_pos;
-		const struct pkt_desc *src = descs + i;
 
 		if (aware_syt && src->syt != CIP_SYT_NO_INFO)
 			dst->syt_offset = compute_syt_offset(src->syt, src->cycle, transfer_delay);
@@ -524,6 +523,7 @@ static void cache_seq(struct amdtp_stream *s, const struct pkt_desc *descs, unsi
 		dst->data_blocks = src->data_blocks;
 
 		cache_pos = (cache_pos + 1) % cache_size;
+		src = amdtp_stream_next_packet_desc(s, src);
 	}
 
 	s->ctx_data.tx.cache.pos = cache_pos;
@@ -881,7 +881,7 @@ static inline u32 compute_ohci_it_cycle(const __be32 ctx_header_tstamp,
 	return increment_ohci_cycle_count(cycle, queue_size);
 }
 
-static int generate_tx_packet_descs(struct amdtp_stream *s, struct pkt_desc *descs,
+static int generate_tx_packet_descs(struct amdtp_stream *s, struct pkt_desc *desc,
 				    const __be32 *ctx_header, unsigned int packet_count,
 				    unsigned int *desc_count)
 {
@@ -894,7 +894,6 @@ static int generate_tx_packet_descs(struct amdtp_stream *s, struct pkt_desc *des
 
 	*desc_count = 0;
 	for (i = 0; i < packet_count; ++i) {
-		struct pkt_desc *desc = descs + *desc_count;
 		unsigned int cycle;
 		bool lost;
 		unsigned int data_blocks;
@@ -918,7 +917,7 @@ static int generate_tx_packet_descs(struct amdtp_stream *s, struct pkt_desc *des
 					desc->data_blocks = 0;
 					desc->data_block_counter = dbc;
 					desc->ctx_payload = NULL;
-					++desc;
+					desc = amdtp_stream_next_packet_desc(s, desc);
 					++(*desc_count);
 				}
 			} else if (s->flags & CIP_JUMBO_PAYLOAD) {
@@ -951,6 +950,7 @@ static int generate_tx_packet_descs(struct amdtp_stream *s, struct pkt_desc *des
 			dbc = (dbc + desc->data_blocks) & 0xff;
 
 		next_cycle = increment_ohci_cycle_count(next_cycle, 1);
+		desc = amdtp_stream_next_packet_desc(s, desc);
 		++(*desc_count);
 		ctx_header += s->ctx_data.tx.ctx_header_size / sizeof(*ctx_header);
 		packet_index = (packet_index + 1) % queue_size;
@@ -973,7 +973,7 @@ static unsigned int compute_syt(unsigned int syt_offset, unsigned int cycle,
 	return syt & CIP_SYT_MASK;
 }
 
-static void generate_rx_packet_descs(struct amdtp_stream *s, struct pkt_desc *descs,
+static void generate_rx_packet_descs(struct amdtp_stream *s, struct pkt_desc *desc,
 				     const __be32 *ctx_header, unsigned int packet_count)
 {
 	struct seq_desc *seq_descs = s->ctx_data.rx.seq.descs;
@@ -986,7 +986,6 @@ static void generate_rx_packet_descs(struct amdtp_stream *s, struct pkt_desc *de
 	pool_seq_descs(s, seq_descs, seq_size, seq_pos, packet_count);
 
 	for (i = 0; i < packet_count; ++i) {
-		struct pkt_desc *desc = descs + i;
 		unsigned int index = (s->packet_index + i) % s->queue_size;
 		const struct seq_desc *seq = seq_descs + seq_pos;
 
@@ -1010,6 +1009,7 @@ static void generate_rx_packet_descs(struct amdtp_stream *s, struct pkt_desc *de
 		desc->ctx_payload = s->buffer.packets[index].buffer;
 
 		seq_pos = (seq_pos + 1) % seq_size;
+		desc = amdtp_stream_next_packet_desc(s, desc);
 
 		++ctx_header;
 	}
@@ -1047,6 +1047,7 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_
 	const __be32 *ctx_header = header;
 	const unsigned int events_per_period = d->events_per_period;
 	unsigned int event_count = s->ctx_data.rx.event_count;
+	struct pkt_desc *desc = s->pkt_descs;
 	unsigned int pkt_header_length;
 	unsigned int packets;
 	bool need_hw_irq;
@@ -1058,9 +1059,9 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_
 	// Calculate the number of packets in buffer and check XRUN.
 	packets = header_length / sizeof(*ctx_header);
 
-	generate_rx_packet_descs(s, s->pkt_descs, ctx_header, packets);
+	generate_rx_packet_descs(s, desc, ctx_header, packets);
 
-	process_ctx_payloads(s, s->pkt_descs, packets);
+	process_ctx_payloads(s, desc, packets);
 
 	if (!(s->flags & CIP_NO_HEADER))
 		pkt_header_length = IT_PKT_HEADER_SIZE_CIP;
@@ -1078,7 +1079,6 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_
 	}
 
 	for (i = 0; i < packets; ++i) {
-		const struct pkt_desc *desc = s->pkt_descs + i;
 		struct {
 			struct fw_iso_packet params;
 			__be32 header[CIP_HEADER_QUADLETS];
@@ -1101,6 +1101,8 @@ static void process_rx_packets(struct fw_iso_context *context, u32 tstamp, size_
 			cancel_stream(s);
 			return;
 		}
+
+		desc = amdtp_stream_next_packet_desc(s, desc);
 	}
 
 	s->ctx_data.rx.event_count = event_count;
@@ -1200,6 +1202,7 @@ static void process_tx_packets(struct fw_iso_context *context, u32 tstamp, size_
 {
 	struct amdtp_stream *s = private_data;
 	__be32 *ctx_header = header;
+	struct pkt_desc *desc = s->pkt_descs;
 	unsigned int packet_count;
 	unsigned int desc_count;
 	int i;
@@ -1212,7 +1215,7 @@ static void process_tx_packets(struct fw_iso_context *context, u32 tstamp, size_
 	packet_count = header_length / s->ctx_data.tx.ctx_header_size;
 
 	desc_count = 0;
-	err = generate_tx_packet_descs(s, s->pkt_descs, ctx_header, packet_count, &desc_count);
+	err = generate_tx_packet_descs(s, desc, ctx_header, packet_count, &desc_count);
 	if (err < 0) {
 		if (err != -EAGAIN) {
 			cancel_stream(s);
@@ -1221,10 +1224,10 @@ static void process_tx_packets(struct fw_iso_context *context, u32 tstamp, size_
 	} else {
 		struct amdtp_domain *d = s->domain;
 
-		process_ctx_payloads(s, s->pkt_descs, desc_count);
+		process_ctx_payloads(s, desc, desc_count);
 
 		if (d->replay.enable)
-			cache_seq(s, s->pkt_descs, desc_count);
+			cache_seq(s, desc, desc_count);
 	}
 
 	for (i = 0; i < packet_count; ++i) {
@@ -1547,7 +1550,8 @@ static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
 	unsigned int ctx_header_size;
 	unsigned int max_ctx_payload_size;
 	enum dma_data_direction dir;
-	int type, tag, err;
+	struct pkt_desc *descs;
+	int i, type, tag, err;
 
 	mutex_lock(&s->mutex);
 
@@ -1655,12 +1659,19 @@ static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
 	else
 		s->tag = TAG_CIP;
 
-	s->pkt_descs = kcalloc(s->queue_size, sizeof(*s->pkt_descs),
-			       GFP_KERNEL);
-	if (!s->pkt_descs) {
+	descs = kcalloc(s->queue_size, sizeof(*descs), GFP_KERNEL);
+	if (!descs) {
 		err = -ENOMEM;
 		goto err_context;
 	}
+	s->pkt_descs = descs;
+
+	INIT_LIST_HEAD(&s->packet_descs_list);
+	for (i = 0; i < s->queue_size; ++i) {
+		INIT_LIST_HEAD(&descs->link);
+		list_add_tail(&descs->link, &s->packet_descs_list);
+		++descs;
+	}
 
 	s->packet_index = 0;
 	do {
@@ -1700,6 +1711,7 @@ static int amdtp_stream_start(struct amdtp_stream *s, int channel, int speed,
 	return 0;
 err_pkt_descs:
 	kfree(s->pkt_descs);
+	s->pkt_descs = NULL;
 err_context:
 	if (s->direction == AMDTP_OUT_STREAM) {
 		kfree(s->ctx_data.rx.seq.descs);
@@ -1794,6 +1806,7 @@ static void amdtp_stream_stop(struct amdtp_stream *s)
 	s->context = ERR_PTR(-1);
 	iso_packets_buffer_destroy(&s->buffer, s->unit);
 	kfree(s->pkt_descs);
+	s->pkt_descs = NULL;
 
 	if (s->direction == AMDTP_OUT_STREAM) {
 		kfree(s->ctx_data.rx.seq.descs);

sound/firewire/amdtp-stream.h

@@ -103,6 +103,7 @@ struct pkt_desc {
 	unsigned int data_blocks;
 	unsigned int data_block_counter;
 	__be32 *ctx_payload;
+	struct list_head link;
 };
 
 struct amdtp_stream;
@@ -126,6 +127,7 @@ struct amdtp_stream {
 	unsigned int queue_size;
 	int packet_index;
 	struct pkt_desc *pkt_descs;
+	struct list_head packet_descs_list;
 	int tag;
 	union {
 		struct {
@@ -276,6 +278,16 @@ static inline void amdtp_stream_pcm_trigger(struct amdtp_stream *s,
 	WRITE_ONCE(s->pcm, pcm);
 }
 
+/**
+ * amdtp_stream_next_packet_desc - retrieve next descriptor for amdtp packet.
+ * @s: the AMDTP stream
+ * @desc: the descriptor of packet
+ *
+ * This macro computes next descriptor so that the list of descriptors behaves circular queue.
+ */
+#define amdtp_stream_next_packet_desc(s, desc) \
+	list_next_entry_circular(desc, &s->packet_descs_list, link)
+
 static inline bool cip_sfc_is_base_44100(enum cip_sfc sfc)
 {
 	return sfc & 1;