[alsa-devel] [PATCH] ALSA: firewire-lib: cache maximum length of payload to reduce function calls

[Takashi Iwai]

On Tue, 11 Apr 2017 13:33:18 +0200,
Takashi Sakamoto wrote:
> 
> 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 at sakamocchi.jp>

Applied, thanks.


Takashi

> ---
>  sound/firewire/amdtp-stream.c | 9 +++++----
>  sound/firewire/amdtp-stream.h | 1 +
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> 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
> diff --git a/sound/firewire/amdtp-stream.h b/sound/firewire/amdtp-stream.h
> index 2bd4de4..7e88317 100644
> --- a/sound/firewire/amdtp-stream.h
> +++ b/sound/firewire/amdtp-stream.h
> @@ -110,6 +110,7 @@ struct amdtp_stream {
>  	int (*handle_packet)(struct amdtp_stream *s,
>  			unsigned int payload_quadlets, unsigned int cycle,
>  			unsigned int index);
> +	unsigned int max_payload_length;
>  
>  	/* For CIP headers. */
>  	unsigned int source_node_id_field;
> -- 
> 2.9.3
>