pci-ntb-howto.rst

  1.. SPDX-License-Identifier: GPL-2.0
  2
  3===================================================================
  4PCI Non-Transparent Bridge (NTB) Endpoint Function (EPF) User Guide
  5===================================================================
  6
  7:Author: Kishon Vijay Abraham I <kishon@ti.com>
  8
  9This document is a guide to help users use pci-epf-ntb function driver
 10and ntb_hw_epf host driver for NTB functionality. The list of steps to
 11be followed in the host side and EP side is given below. For the hardware
 12configuration and internals of NTB using configurable endpoints see
 13Documentation/PCI/endpoint/pci-ntb-function.rst
 14
 15Endpoint Device
 16===============
 17
 18Endpoint Controller Devices
 19---------------------------
 20
 21For implementing NTB functionality at least two endpoint controller devices
 22are required.
 23
 24To find the list of endpoint controller devices in the system::
 25
 26	# ls /sys/class/pci_epc/
 27	2900000.pcie-ep  2910000.pcie-ep
 28
 29If PCI_ENDPOINT_CONFIGFS is enabled::
 30
 31	# ls /sys/kernel/config/pci_ep/controllers
 32	2900000.pcie-ep  2910000.pcie-ep
 33
 34
 35Endpoint Function Drivers
 36-------------------------
 37
 38To find the list of endpoint function drivers in the system::
 39
 40	# ls /sys/bus/pci-epf/drivers
 41	pci_epf_ntb   pci_epf_ntb
 42
 43If PCI_ENDPOINT_CONFIGFS is enabled::
 44
 45	# ls /sys/kernel/config/pci_ep/functions
 46	pci_epf_ntb   pci_epf_ntb
 47
 48
 49Creating pci-epf-ntb Device
 50----------------------------
 51
 52PCI endpoint function device can be created using the configfs. To create
 53pci-epf-ntb device, the following commands can be used::
 54
 55	# mount -t configfs none /sys/kernel/config
 56	# cd /sys/kernel/config/pci_ep/
 57	# mkdir functions/pci_epf_ntb/func1
 58
 59The "mkdir func1" above creates the pci-epf-ntb function device that will
 60be probed by pci_epf_ntb driver.
 61
 62The PCI endpoint framework populates the directory with the following
 63configurable fields::
 64
 65	# ls functions/pci_epf_ntb/func1
 66	baseclass_code    deviceid          msi_interrupts    pci-epf-ntb.0
 67	progif_code       secondary         subsys_id         vendorid
 68	cache_line_size   interrupt_pin     msix_interrupts   primary
 69	revid             subclass_code     subsys_vendor_id
 70
 71The PCI endpoint function driver populates these entries with default values
 72when the device is bound to the driver. The pci-epf-ntb driver populates
 73vendorid with 0xffff and interrupt_pin with 0x0001::
 74
 75	# cat functions/pci_epf_ntb/func1/vendorid
 76	0xffff
 77	# cat functions/pci_epf_ntb/func1/interrupt_pin
 78	0x0001
 79
 80
 81Configuring pci-epf-ntb Device
 82-------------------------------
 83
 84The user can configure the pci-epf-ntb device using its configfs entry. In order
 85to change the vendorid and the deviceid, the following
 86commands can be used::
 87
 88	# echo 0x104c > functions/pci_epf_ntb/func1/vendorid
 89	# echo 0xb00d > functions/pci_epf_ntb/func1/deviceid
 90
 91The PCI endpoint framework also automatically creates a sub-directory in the
 92function attribute directory. This sub-directory has the same name as the name
 93of the function device and is populated with the following NTB specific
 94attributes that can be configured by the user::
 95
 96	# ls functions/pci_epf_ntb/func1/pci_epf_ntb.0/
 97	db_count    mw1         mw2         mw3         mw4         num_mws
 98	spad_count
 99
100A sample configuration for NTB function is given below::
101
102	# echo 4 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/db_count
103	# echo 128 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/spad_count
104	# echo 2 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/num_mws
105	# echo 0x100000 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/mw1
106	# echo 0x100000 > functions/pci_epf_ntb/func1/pci_epf_ntb.0/mw2
107
108Binding pci-epf-ntb Device to EP Controller
109--------------------------------------------
110
111NTB function device should be attached to two PCI endpoint controllers
112connected to the two hosts. Use the 'primary' and 'secondary' entries
113inside NTB function device to attach one PCI endpoint controller to
114primary interface and the other PCI endpoint controller to the secondary
115interface::
116
117	# ln -s controllers/2900000.pcie-ep/ functions/pci-epf-ntb/func1/primary
118	# ln -s controllers/2910000.pcie-ep/ functions/pci-epf-ntb/func1/secondary
119
120Once the above step is completed, both the PCI endpoint controllers are ready to
121establish a link with the host.
122
123
124Start the Link
125--------------
126
127In order for the endpoint device to establish a link with the host, the _start_
128field should be populated with '1'. For NTB, both the PCI endpoint controllers
129should establish link with the host::
130
131	# echo 1 > controllers/2900000.pcie-ep/start
132	# echo 1 > controllers/2910000.pcie-ep/start
133
134
135RootComplex Device
136==================
137
138lspci Output
139------------
140
141Note that the devices listed here correspond to the values populated in
142"Creating pci-epf-ntb Device" section above::
143
144	# lspci
145	0000:00:00.0 PCI bridge: Texas Instruments Device b00d
146	0000:01:00.0 RAM memory: Texas Instruments Device b00d
147
148
149Using ntb_hw_epf Device
150-----------------------
151
152The host side software follows the standard NTB software architecture in Linux.
153All the existing client side NTB utilities like NTB Transport Client and NTB
154Netdev, NTB Ping Pong Test Client and NTB Tool Test Client can be used with NTB
155function device.
156
157For more information on NTB see
158:doc:`Non-Transparent Bridge <../../driver-api/ntb>`