9.9. PCI Non-Transparent Bridge (NTB) Endpoint Function (EPF) User Guide — The Linux Kernel 7.0.11-gnu-zen1-1-zen documentation

# 9.9. PCI Non-Transparent Bridge (NTB) Endpoint Function (EPF) User Guide

Author:

  Frank Li <Frank.Li@nxp.com>

This document is a guide to help users use pci-epf-vntb 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 PCI vNTB Function

## 9.9.1. Endpoint Device

### 9.9.1.1. Endpoint Controller Devices

To find the list of endpoint controller devices in the system:

    # ls /sys/class/pci_epc/
      5f010000.pcie_ep

If PCI_ENDPOINT_CONFIGFS is enabled:

    # ls /sys/kernel/config/pci_ep/controllers
      5f010000.pcie_ep

### 9.9.1.2. 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_test  pci_epf_vntb

If PCI_ENDPOINT_CONFIGFS is enabled:

    # ls /sys/kernel/config/pci_ep/functions
    pci_epf_ntb  pci_epf_test  pci_epf_vntb

### 9.9.1.3. Creating pci-epf-vntb Device

PCI endpoint function device can be created using the configfs. To create pci-epf-vntb device, the following commands can be used:

    # mount -t configfs none /sys/kernel/config
    # cd /sys/kernel/config/pci_ep/
    # mkdir functions/pci_epf_vntb/func1

The “mkdir func1” above creates the pci-epf-vntb function device that will be probed by pci_epf_vntb driver.

The PCI endpoint framework populates the directory with the following configurable fields:

    # ls functions/pci_epf_vntb/func1
    baseclass_code    deviceid          msi_interrupts    pci-epf-vntb.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-vntb driver populates vendorid with 0xffff and interrupt_pin with 0x0001:

    # cat functions/pci_epf_vntb/func1/vendorid
    0xffff
    # cat functions/pci_epf_vntb/func1/interrupt_pin
    0x0001

### 9.9.1.4. Configuring pci-epf-vntb Device

The user can configure the pci-epf-vntb device using its configfs entry. In order to change the vendorid and the deviceid, the following commands can be used:

    # echo 0x1957 > functions/pci_epf_vntb/func1/vendorid
    # echo 0x0809 > functions/pci_epf_vntb/func1/deviceid

The PCI endpoint framework also automatically creates a sub-directory in the function attribute directory. This sub-directory has the same name as the name of the function device and is populated with the following NTB specific attributes that can be configured by the user:

    # ls functions/pci_epf_vntb/func1/pci_epf_vntb.0/
    ctrl_bar  db_count  mw1_bar  mw2_bar  mw3_bar  mw4_bar  spad_count
    db_bar    mw1       mw2      mw3      mw4      num_mws  vbus_number
    vntb_vid  vntb_pid

A sample configuration for NTB function is given below:

    # echo 4 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/db_count
    # echo 128 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/spad_count
    # echo 1 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/num_mws
    # echo 0x100000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1

By default, each construct is assigned a BAR, as needed and in order. Should a specific BAR setup be required by the platform, BAR may be assigned to each construct using the related `XYZ_bar` entry.

A sample configuration for virtual NTB driver for virtual PCI bus:

    # echo 0x1957 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_vid
    # echo 0x080A > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid
    # echo 0x10 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vbus_number

### 9.9.1.5. Binding pci-epf-vntb Device to EP Controller

NTB function device should be attached to PCI endpoint controllers connected to the host.

> # ln -s controllers/5f010000.pcie_ep functions/pci_epf_vntb/func1/primary

Once the above step is completed, the PCI endpoint controllers are ready to establish a link with the host.

### 9.9.1.6. 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 (imx8 don’t need this steps):

    # echo 1 > controllers/5f010000.pcie_ep/start

## 9.9.2. RootComplex Device

### 9.9.2.1. lspci Output at Host side

Note that the devices listed here correspond to the values populated in “Creating pci-epf-vntb Device” section above:

    # lspci
    00:00.0 PCI bridge: Freescale Semiconductor Inc Device 0000 (rev 01)
    01:00.0 RAM memory: Freescale Semiconductor Inc Device 0809

## 9.9.3. Endpoint Device / Virtual PCI bus

### 9.9.3.1. lspci Output at EP Side / Virtual PCI bus

Note that the devices listed here correspond to the values populated in “Creating pci-epf-vntb Device” section above:

    # lspci
    10:00.0 Unassigned class [ffff]: Dawicontrol Computersysteme GmbH Device 1234 (rev ff)

### 9.9.3.2. 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 Non-Transparent Bridge