Flex bus protocol negotiation and enabling sequence

A system comprising:

• an endpoint device;
• and
• a host device coupled to the endpoint device by a link, the host device comprising:
• a processor, and
• a root complex;
• the root complex to send, to the endpoint device, a first stream of modified training sequence 1 (TS1) ordered sets to the endpoint device, each modified TS1 ordered set in the first stream of modified TS1 ordered sets comprising information to advertise a low latency capability;
• the endpoint device to send, to the root complex, a second stream of modified TS1 ordered sets, each modified TS1 ordered set in the second stream of modified TS1 ordered sets comprising information to indicate a low latency capability of the endpoint device;
• and
• the root complex to send a stream of modified training sequence 2 (TS2) ordered sets to the endpoint device, each modified TS2 ordered set of the stream of modified TS2 ordered sets comprising information to indicate, to the endpoint device, the low latency capability to use on the link.

An apparatus comprising:

• an endpoint device to:
• receive, from a central processing unit (CPU), a first stream of modified training sequence 1 (TS1) ordered sets, each modified TS1 ordered set in the first stream of modified TS1 comprising information to advertise a low latency capability;
• send a second stream of modified TS1 ordered sets to the CPU, each modified TS1 ordered set in the second stream of TS1 ordered sets from the endpoint device comprising information to indicate a low latency capability of the endpoint;
• receive, from the CPU, a first stream of modified training sequence 2 (TS2) ordered sets, each of the modified TS2 ordered sets in the first stream of modified TS2 ordered sets comprising information to indicate a low latency capability to use on the link;
• and
• send, to the CPU, a second stream of modified TS2 ordered sets to confirm the low latency capability to use on the link.

A method performed by a host device, the method comprising:

• sending, to an endpoint device, a first stream of modified training sequence 1 (TS1) ordered sets to advertise a capability to prepare data for transmission either a Peripheral Component Interconnect Express (PCIe) protocol or an accelerator link protocol;
• receiving, from the endpoint device, a second stream of modified TS1 ordered sets;
• identifying, from the second stream of modified TS1 ordered sets, a low latency capability for the endpoint device;
• determining to use the low latency capability;
• and
• sending a stream of modified training sequence 2 (TS2) ordered sets to the endpoint to inform the endpoint device to use the low latency capability.