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.. SPDX-License-Identifier: GPL-2.0
PCI Non-Transparent Bridge (NTB) Endpoint Function (EPF) User Guide
:Author: Kishon Vijay Abraham I <>
This document is a guide to help users use pci-epf-ntb function driver
and ntb_hw_epf host driver for NTB functionality. The list of steps to
be followed in the host side and EP side is given below. For the hardware
configuration and internals of NTB using configurable endpoints see
Endpoint Device
Endpoint Controller Devices
For implementing NTB functionality at least two endpoint controller devices
are required.
To find the list of endpoint controller devices in the system::
# ls /sys/class/pci_epc/
2900000.pcie-ep 2910000.pcie-ep
# ls /sys/kernel/config/pci_ep/controllers
2900000.pcie-ep 2910000.pcie-ep
Endpoint Function Drivers
To find the list of endpoint function drivers in the system::
# ls /sys/bus/pci-epf/drivers
pci_epf_ntb pci_epf_ntb
# ls /sys/kernel/config/pci_ep/functions
pci_epf_ntb pci_epf_ntb
Creating pci-epf-ntb Device
PCI endpoint function device can be created using the configfs. To create
pci-epf-ntb device, the following commands can be used::
# mount -t configfs none /sys/kernel/config
# cd /sys/kernel/config/pci_ep/
# mkdir functions/pci_epf_ntb/func1
The "mkdir func1" above creates the pci-epf-ntb function device that will
be probed by pci_epf_ntb driver.
The PCI endpoint framework populates the directory with the following
configurable fields::
# ls functions/pci_epf_ntb/func1
baseclass_code deviceid msi_interrupts pci-epf-ntb.0
progif_code secondary subsys_id vendorid
cache_line_size interrupt_pin msix_interrupts primary
revid subclass_code subsys_vendor_id
The PCI endpoint function driver populates these entries with default values
when the device is bound to the driver. The pci-epf-ntb driver populates
vendorid with 0xffff and interrupt_pin with 0x0001::
# cat functions/pci_epf_ntb/func1/vendorid
# cat functions/pci_epf_ntb/func1/interrupt_pin
Configuring pci-epf-ntb Device
The user can configure the pci-epf-ntb device using its configfs entry. In order
to change the vendorid and the deviceid, the following
commands can be used::
# echo 0x104c > functions/pci_epf_ntb/func1/vendorid
# echo 0xb00d > functions/pci_epf_ntb/func1/deviceid
In order to configure NTB specific attributes, a new sub-directory to func1
should be created::
# mkdir functions/pci_epf_ntb/func1/pci_epf_ntb.0/
The NTB function driver will populate this directory with various attributes
that can be configured by the user::
# ls functions/pci_epf_ntb/func1/pci_epf_ntb.0/
db_count mw1 mw2 mw3 mw4 num_mws
A sample configuration for NTB function is given below::
# echo 4 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/db_count
# echo 128 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/spad_count
# echo 2 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/num_mws
# echo 0x100000 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/mw1
# echo 0x100000 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/mw2
Binding pci-epf-ntb Device to EP Controller
NTB function device should be attached to two PCI endpoint controllers
connected to the two hosts. Use the 'primary' and 'secondary' entries
inside NTB function device to attach one PCI endpoint controller to
primary interface and the other PCI endpoint controller to the secondary
# ln -s controllers/2900000.pcie-ep/ functions/pci-epf-ntb/func1/primary
# ln -s controllers/2910000.pcie-ep/ functions/pci-epf-ntb/func1/secondary
Once the above step is completed, both the PCI endpoint controllers are ready to
establish a link with the host.
Start the Link
In order for the endpoint device to establish a link with the host, the _start_
field should be populated with '1'. For NTB, both the PCI endpoint controllers
should establish link with the host::
# echo 1 > controllers/2900000.pcie-ep/start
# echo 1 > controllers/2910000.pcie-ep/start
RootComplex Device
lspci Output
Note that the devices listed here correspond to the values populated in
"Creating pci-epf-ntb Device" section above::
# lspci
0000:00:00.0 PCI bridge: Texas Instruments Device b00d
0000:01:00.0 RAM memory: Texas Instruments Device b00d
Using ntb_hw_epf Device
The host side software follows the standard NTB software architecture in Linux.
All the existing client side NTB utilities like NTB Transport Client and NTB
Netdev, NTB Ping Pong Test Client and NTB Tool Test Client can be used with NTB
function device.
For more information on NTB see
:doc:`Non-Transparent Bridge <../../driver-api/ntb>`