Time-Sensitive Networking (TSN) is a set of standards under development by the Time-Sensitive Networking task group of the IEEE 802.1 working group.
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TSN kernel drivers are currently support supported in Xilinx Linux staging area: https://github.com/Xilinx/linux-xlnx/tree/xilinx-v2022.1/drivers/staging/xilinx-tsn
TSN user space utilities and sample configurations are provided to enable TSN functionality. Please refer to the TSN SW user guide and the following sections for more details.
Kernel Configuration
The following config options should be enabled in order to build the TSN Subsystem:
CONFIG_XILINX_TSN
CONFIG_AXIENET_HAS_TADMA
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The following additional config is required/selected by the TSN subsystem:
CONFIG_NET_SWITCHDEV
CONFIG_STP
CONFIG_NETFILTER
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Please refer to PL Ethernet and DMA documentation for additional information: Documentation/devicetree/bindings/net/xilinx_axienet.txt
For more details on phy bindings please refer "Documentation/devicetree/bindings/net/phy.txt"
TSN System
- Xilinx’s TSN IP Switch have has three ports Endpoint (Port 0), MAC1 (Port 1) and MAC2 (Port 2)
- Endpoint is connected to MCDMA (Multichannel DMA), each MCDMA channel is a dedicated channel for each type of traffic, i.e. Best Effort, Scheduled Traffic and Reserved. There could be other use cases where there would be separate channels for management traffic
- MAC1 is connected to external world by PHY1
- MAC2 is connected to external world by PHY2
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You would observe that every second 12 ST packets are sent of which 8 packets are sent in the 100us of 10 ms cycle and the rest 4 packets are sent in the next cycle.
As we can see in the above picture, from 4th packet until 11th packet (8 packets) are received sequentially and the next packet starts after 10ms delay (packet no. 12).
Running IPIC:
IP interception translates the transmit packet with the configured source, destination MAC addresses, VLAN ID and PCP values if the packets' IPv4 tuples (source IP, destination IP, DSCP, protocol, source port number and destination port number) match. IPIC module maintains hash entries of IPv4 tuples and if the out-going packets' tuple data match with that of hash entries , translates the IP stream.
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Make sure iperf3 server is run at the receiver as below and observe the received packets with destination MAC, source MAC addresses and VLAN ID.
- iperf3 -s
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When the system has preemption capabilities, openlldp is run to detect frame preemption capabilities of the peer and if the peer has the capabilities, to enable the preemption.
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0th bit of preemption enable register is 1 implying preemption is enabled, and 31st bit of preemption control status register is 1 implying preemption is active.
Steps to demonstrate Preemption
1. Change MAC addresses (if two xilinx boards are used back to back).
2. Launch lldpad daemon.
# lldpad -d
# lldptool set-lldp -i eth1 adminStatus=rxtx
3. Setup lldpad for additional ethernet capabilities TLV. Make sure preemption is enabled and active.
#lldptool -i eth1 set-tlv -V addEth enableTx=yes
4. Bring up the network interfaces.
5. Establish PTP sync, run qbv on tx side.
6. Add switch CAM entries as necessary, and send traffic, both ST and BE (express and preemptable) from tx side.
7. Run br_prog <interface name> stats, check if the TX MAC MERGE FRAGMENT COUNT(on tx side), RX MAC MERGE FRAGMENT COUNT(On rx side), are increasing.
Running Spanning Tree Protocol
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