scamp-p2p.c File Reference

P2P packet handling for SC&MP. More...

#include "spinnaker.h"
#include "sark.h"
#include "scamp.h"
#include "spinn_net.h"

Data Structures
struct	rx_desc_t
	P2P channel state structure: receiver. More...
struct	tx_desc_t
	P2P channel state structure: transmitter. More...

Macros
#define	P2P_NUM_STR   8
	Number of streams.

Enumerations
enum	p2p_tx_state {   TX_IDLE = 0 , TX_OPEN_REQ = 1 , TX_OPEN = 2 , TX_RETRY = 3 ,   TX_CLOSE = 4 }
	Possible states in P2P protocol: transmitter side.
enum	p2p_rx_state { RX_IDLE = 0 , RX_OPEN = 1 , RX_CLOSE_REQ = 2 }
	Possible states in P2P protocol: receiver side.
enum	p2p_stats_indices {   DATA_TO = 0 , ACK_TO = 1 , OPEN_TO = 2 , CLOSE_TO = 3 ,   P2P_SENDS = 4 , P2P_OPENS = 5 , P2P_BUSY1 = 6 , P2P_BUSY2 = 7 ,   P2P_REJECTS = 8 , TCOUNT = 9 , OPEN_DUP = 10 , TX_FAIL = 11 ,   OPEN_EVENT = 12 , P2P_OPEN_N = 16 }
	Indices into p2p_stats. More...

Functions
void	desc_init (void)
	initialise TX and RX descriptors
static void	p2p_send_data (uint data, uint addr)
	Send a P2P data packet. Delegates to pkt_tx()
static uint	p2p_send_ctl (uint ctrl, uint addr, uint data)
	Send a P2P control packet. Delegates to pkt_tx()
void	p2p_data_ack (uint data, uint srce)
	Received ACK from receiver. Cancel ack timeout and update tx_desc.
void	p2p_close_req (uint data, uint srce)
	Received CLOSE_REQ from receiver.
void	p2p_ack_timeout (uint txd, uint a2)
	Timed out waiting for data ACK from receiver.
void	p2p_open_timeout (uint a, uint b)
	Timeout handler during channel opening phase.
uint	p2p_send_msg (uint addr, sdp_msg_t *msg)
	Send an SDP message to another SCAMP instance.
void	p2p_data_timeout (uint rxd, uint a2)
	Timed out waiting for "seq_len" data packets. Send P2P_DATA_ACK with current mask and restart timeout.
void	p2p_open_ack (uint data, uint srce)
	Received OPEN_ACK packet.
void	p2p_open_req (uint data, uint addr)
	Another SCAMP has asked for an open channel.
void	p2p_close_timeout (uint rxd, uint rid)
	Timed out waiting for CLOSE_ACK. Repeat P2P_CLOSE_REQ a few times then give up.
void	p2p_close_ack (uint data, uint srce)
	Received an acknowledge that a channel has been closed.
void	p2p_rcv_data (uint data, uint addr)
	Receive data on channel.
uint	p2p_send_ping (uint addr, uint link)
void	p2p_ping (uint data, uint addr)
void	p2p_req_count (uint addr, uint app_id, uint state)
uint	n_cores_in_state (uint app_id, uint state)
void	p2p_count (uint data, uint addr)
void	p2p_count_resp (uint data, uint addr)
void	p2p_rcv_ctrl (uint data, uint addr)
	Received P2P control packet.

Variables
tx_desc_t	tx_desc
	Transmitter state descriptor. Transmission is a foreground task.
rx_desc_t	rx_desc_table [P2P_NUM_STR]
	Receiver state descriptors. Reception is a background task.
uint	p2p_stats [32]
	Peer-to-peer statistics table.
const uint	open_req_retry = 16
	Number of retries for an open request.
const uint	open_ack_retry = 4
	Number of retries for an open acknowledge.
const uint	data_ack_retry = 4
	Number of retries for a data acknowledge.
const uint	close_req_retry = 4
	Number of retries for a close request.
const uint	open_ack_time = 250
	Timeout on open acknowledge, in μs.
const uint	data_ack_time = 3000
	Timeout on data acknowledge, in μs.
const uint	data_time = 500
	Timeout on data, in μs.
const uint	close_ack_time = 250
	Timeout on close acknowledge, in μs.
volatile uint	pp_ping_count [NUM_LINKS]
	Reserved for performing P2P pings.
volatile uint	p2p_count_result
	Reserved for performing a P2P count operation.
volatile uint	p2p_count_n_results
uint	p2p_count_id

Detailed Description

P2P packet handling for SC&MP.

Copyright

© The University of Manchester - 2009-2019

Author

Steve Temple, APT Group, School of Computer Science

---

Data Structure Documentation

rx_desc_t

struct rx_desc_t

P2P channel state structure: receiver.

Data Fields
uchar	state
uchar	seq_len
uchar	done
uchar	tid
uchar	tcount
uchar	ctrl
uchar	phase
ushort	mask
ushort	new_mask
uint	srce
uchar *	base
uchar *	limit
sdp_msg_t *	msg
event_t *	event	pre-allocated reused event
uint	event_id

tx_desc_t

struct tx_desc_t

P2P channel state structure: transmitter.

Data Fields
uchar	seq_len
uchar	seq
uchar	odd
uchar	done
uchar	state
uchar	rid
uchar	tid
uchar	tcount
uchar	rc
uchar	phase
volatile uchar	ack
ushort	mask
uint	dest
uchar *	base
uchar *	limit
event_t *	event	pre-allocated reused event
uint	event_id

Enumeration Type Documentation

p2p_stats_indices

enum p2p_stats_indices

Indices into p2p_stats.

Enumerator
DATA_TO	Timeouts waiting for data.
ACK_TO	Timeouts waiting for acknowledgements.
OPEN_TO	Timeouts during channel open (request)
CLOSE_TO	Timeouts during channel close.
P2P_SENDS	Number of sends.
P2P_OPENS	Number of opens.
P2P_BUSY1	Number of times busy due to no more streams.
P2P_BUSY2	Number of times busy due to no more SDP buffers.
P2P_REJECTS	Number of times message was rejected.
TCOUNT	Most recent value of tx_desc_t::tcount.
OPEN_DUP	Number of times a channel was already open.
TX_FAIL	Number of transmission failures.
OPEN_EVENT	Timeouts during open (timeout handler)
P2P_OPEN_N	Base for array of counters for tracking channel usage.

Function Documentation

p2p_send_data()

static void p2p_send_data ( uint  data, uint  addr  )

static

Send a P2P data packet. Delegates to pkt_tx()

Parameters

[in]	data	Payload of the message
[in]	addr	Where to send to

p2p_send_ctl()

static uint p2p_send_ctl ( uint  ctrl, uint  addr, uint  data  )

static

Send a P2P control packet. Delegates to pkt_tx()

Parameters

[in]	ctrl	What message to send
[in]	addr	Where to send to
[in]	data	Payload of the message

p2p_data_ack()

void p2p_data_ack	(	uint	data,
		uint	srce
	)

Received ACK from receiver. Cancel ack timeout and update tx_desc.

     +-------+-----+-+---+-+---------+---------------+---------------+
     |       |     | |   |P|         |                               |
Data |  Sum  | 001 |1| 00|H|   TID   |           Ack mask            |
Ack  |       |     | |   |A|         |                               |
     +-------+-----+-+---+-+---------+---------------+---------------+

Parameters

[in]	data	The payload from the packet
[in]	srce	The sender address (lower 16 bits) from the packet

p2p_close_req()

void p2p_close_req	(	uint	data,
		uint	srce
	)

Received CLOSE_REQ from receiver.

If TX_OPEN then tidy up tx_desc. In any case, send a CLOSE_ACK back to receiver.

Parameters

[in]	data	The payload from the packet
[in]	srce	The sender address (lower 16 bits) from the packet

p2p_ack_timeout()

void p2p_ack_timeout	(	uint	txd,
		uint	a2
	)

Timed out waiting for data ACK from receiver.

This suggests that the receiver has died so close the connection.

Parameters

[out]	txd	Transmit descriptor
[in]	a2	ignored

p2p_open_timeout()

void p2p_open_timeout	(	uint	a,
		uint	b
	)

Timeout handler during channel opening phase.

Parameters

[out]	a	pointer to transmit descriptor
[in]	b	code to write to tx_desc_t::ack on timeout

p2p_send_msg()

uint p2p_send_msg	(	uint	addr,
		sdp_msg_t *	msg
	)

Send an SDP message to another SCAMP instance.

Parameters

[in]	addr	the P2P address of the SCAMP to send to
[in]	msg	the message to send, presumably for either the target SCAMP or a core that that SCAMP can deliver to

Returns

result code saying whether message sending was successful

p2p_data_timeout()

void p2p_data_timeout	(	uint	rxd,
		uint	a2
	)

Timed out waiting for "seq_len" data packets. Send P2P_DATA_ACK with current mask and restart timeout.

Parameters

[in,out]	rxd	channel receiver descriptor
[in]	a2	ignored

p2p_open_ack()

void p2p_open_ack	(	uint	data,
		uint	srce
	)

Received OPEN_ACK packet.

If RX_BUSY do nothing so that timeout will expire (and we keep trying). Otherwise update tx_desc and cancel timeout.

Parameters

[in]	data	The payload from the packet
[in]	srce	The sender address (lower 16 bits) from the packet

p2p_open_req()

void p2p_open_req	(	uint	data,
		uint	addr
	)

Another SCAMP has asked for an open channel.

Parameters

[in]	data	The payload from the packet
[in]	addr	The sender address (lower 16 bits) from the packet

p2p_close_timeout()

void p2p_close_timeout	(	uint	rxd,
		uint	rid
	)

Timed out waiting for CLOSE_ACK. Repeat P2P_CLOSE_REQ a few times then give up.

State should be RX_CLOSE_REQ

Parameters

[in,out]	rxd	Receive descriptor
[in]	rid	Receiver ID

p2p_close_ack()

void p2p_close_ack	(	uint	data,
		uint	srce
	)

Received an acknowledge that a channel has been closed.

Parameters

[in]	data	The payload from the packet
[in]	srce	The sender address (lower 16 bits) from the packet

p2p_rcv_data()

void p2p_rcv_data	(	uint	data,
		uint	addr
	)

Receive data on channel.

May write 1 or 2 bytes beyond end of buffer (buffer has pad word)

Parameters

[in]	data	The payload from the packet
[in]	addr	The sender address (lower 16 bits) from the packet

p2p_rcv_ctrl()

void p2p_rcv_ctrl	(	uint	data,
		uint	addr
	)

Received P2P control packet.

Delegates to:

• p2p_open_req()
• p2p_open_ack()
• p2p_data_ack()
• p2p_close_req()
• p2p_close_ack()

Parameters

[in]	data	The payload from the packet
[in]	addr	The sender address (lower 16 bits) from the packet