ALSA: firewire-lib: cache maximum length of payload to reduce function calls
During packet streaming, maximum length of payload for isochronous packet
is invariable, therefore no need to recalculate. Current ALSA IEC 61883-1/6
engine calls a function to calculate it 8,000 or more times per second
for incoming packet processing.
This commit adds a member to have maximum length of payload into 'struct
amdtp_stream', to reduces the function calls. At first callback from
isochronous context, the length is calculated and stored for later
processing.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index f6af8e6..9e6f54f 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -412,8 +412,7 @@ static inline int queue_out_packet(struct amdtp_stream *s,
static inline int queue_in_packet(struct amdtp_stream *s)
{
- return queue_packet(s, IN_PACKET_HEADER_SIZE,
- amdtp_stream_get_max_payload(s));
+ return queue_packet(s, IN_PACKET_HEADER_SIZE, s->max_payload_length);
}
static int handle_out_packet(struct amdtp_stream *s,
@@ -713,12 +712,12 @@ static void in_stream_callback(struct fw_iso_context *context, u32 tstamp,
cycle = decrement_cycle_count(cycle, packets);
/* For buffer-over-run prevention. */
- max_payload_length = amdtp_stream_get_max_payload(s);
+ max_payload_length = s->max_payload_length;
for (i = 0; i < packets; i++) {
cycle = increment_cycle_count(cycle, 1);
- /* The number of quadlets in this packet */
+ /* The number of bytes in this packet */
payload_length =
(be32_to_cpu(headers[i]) >> ISO_DATA_LENGTH_SHIFT);
if (payload_length > max_payload_length) {
@@ -751,6 +750,8 @@ static void amdtp_stream_first_callback(struct fw_iso_context *context,
u32 cycle;
unsigned int packets;
+ s->max_payload_length = amdtp_stream_get_max_payload(s);
+
/*
* For in-stream, first packet has come.
* For out-stream, prepared to transmit first packet