Flit-based parallel-forward error correction and parity
A flit-based packetization approach is used for transmitting information between electronic components. A protocol stack can generate transaction layer packets from information received from a transmitting device, assemble the transaction layer packets into one or more flits, and protect the flits with a flit-level cyclic redundancy check (CRC) scheme and a flit-level forward error correction or parallel-forward error correction (FEC) scheme. Flit-level FEC schemes can provide improved latencies and efficiencies over per-lane FEC schemes. To improve retry probability, flits can contain information indicating whether immediately preceding flits are null flits. Receivers can avoid sending a retry request for a corrupted flit if a seceding flit indicates the corrupted flit is a null fit. Parity flits can be used to protect groups of flits and correct single-flit errors.
1. An apparatus comprising:
a port to send information on multiple lanes of a link;
protocol stack circuitry to:
create a transaction layer packet (TLP) to be transmitted on the link;
calculate error correcting code (ECC) for all of the transaction layer packets;
generate a flit comprising the transaction layer packet;
interleave the ECC in multiple symbols of the flit; and
cause the port to send the flit on the multiple lanes.
2. The apparatus of claim 1 , the protocol stack to interleave the ECC using 3-way interleaving.
3. The apparatus of claim 1 , wherein the ECC comprises parity and check bits.
4. The apparatus of claim 1 , the protocol stack to:
create data link layer packets (DLLP); and
encode the flit with data link layer packet into symbols after the transaction layer packets and before the ECC.
5. The apparatus of claim 4 , wherein the protocol stack is further to:
calculate cyclic redundancy check (CRC) code for the transaction layer packets, the CRC code comprising eight bytes;
encode eight consecutive symbols of the flit with the CRC code after the transaction layer packets.
6. The apparatus of claim 5 , wherein the CRC code is to check the TLPs and the DLLPs in the flit.
7. The apparatus of claim 5 , wherein the ECC is interleaved into the flit after the CRC code.
8. The apparatus of claim 5 , wherein the ECC is to check the TLPs, the DLLPs, and the CRC code.
9. The apparatus of claim 1 , wherein the ECC comprises six bytes interleaved across six symbols of the flit.
10. A method, comprising:
creating transaction layer packet (TLP) to be transmitted on multiple lanes of a link;
calculating error correcting code (ECC) for the transaction layer packet;
generating a flit comprising the transaction layer packets;
interleaving the ECC in multiple symbols of the flit, wherein the ECC is for the entire Flit payload; and
transmitting the flit on the link.
11. The method of claim 10 , further comprising interleaving the ECC using 3-way interleaving.
12. The method of claim 10 , wherein the ECC comprises parity and check bits.
13. The method of claim 10 , further comprising:
generating data link layer packets (DLLP); and
encoding the flit with data link layer packet into symbols after the transaction layer packets and before the ECC.
14. The method of claim 13 , further comprising:
calculating cyclic redundancy check (CRC) code for the transaction layer packets, the CRC code comprising eight bytes; and
encoding eight consecutive symbols of the flit with the CRC code after the transaction layer packets.
15. The method of claim 14 , wherein the CRC code is to check the TLPs and the DLLPs in the flit.
16. The method of claim 14 , wherein the ECC is interleaved into the flit after the CRC code.
17. The method of claim 14 , wherein the ECC is to check the TLPs, the DLLPs, and the CRC code.
18. The method of claim 10 , wherein the ECC comprises six bytes interleaved across six symbols of the flit.
19. A system comprising:
a link connecting a transmitter to a receiver;
the transmitter comprising a transmitter-side protocol stack circuitry to:
create transaction layer packets (TLP) to be transmitted on the link,
calculate error correcting code (ECC) for the transaction layer packets,
generate a flit comprising the transaction layer packets,
interleave the ECC in multiple symbols of the flit, and
transmit the flit on the link; and
the receiver comprising receiver-side protocol stack circuitry to:
receive the flit from across the link, and
check the TLP for errors using ECC received in the flit.
20. The system of claim 19 , the transmitter-side protocol stack circuitry to interleave the ECC using 3-way interleaving.
21. The system of claim 19 , the transmitter-side protocol stack circuitry to:
generate data link layer packets (DLLP); and
encode the flit with data link layer packet into symbols after the transaction layer packets and before the ECC.
22. The system of claim 21 , wherein the transmitter-side protocol stack circuitry is to:
calculate cyclic redundancy check (CRC) code for the transaction layer packets, the CRC code comprising eight bytes;
encode eight consecutive symbols of the flit with the CRC code after the transaction layer packets.
23. The system of claim 22 , wherein the CRC code is to check the TLPs and the DLLPs in the flit.
24. The system of claim 22 , wherein:
the ECC is interleaved into the flit after the CRC code; and
the ECC is to check the TLPs, the DLLPs, and the CRC code.
25. The system of claim 19 , wherein the ECC comprises six bytes interleaved across six symbols of the flit.
26. An apparatus comprising:
protocol stack circuitry to:
generate a flow control unit (Flit), the Flit comprising a predetermined number of bytes;
the Flit comprising:
a transaction layer packet (TLP) payload to occupy a first number of bytes of the Flit; and
error correcting code (ECC) to occupy six bytes of the Flit, the ECC to protect each byte of the TLP payload.
27. The apparatus of claim 26 , the protocol stack circuitry to:
calculate cyclic redundancy check (CRC) code for the transaction layer packet, the CRC code comprising eight bytes;
encode eight consecutive symbols of the flit with the CRC code after the transaction layer packets, the CRC to check the entire TLP payload.