[PATCH v7 18/18] Documentation: PCI: Add userguide for PCI endpoint NTB function

From: Kishon Vijay Abraham I
Date: Wed Sep 30 2020 - 11:38:44 EST

Add documentation to help users use pci-epf-ntb function driver and
existing host side NTB infrastructure for NTB functionality.

Signed-off-by: Kishon Vijay Abraham I <kishon@xxxxxx>
Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
---
Documentation/PCI/endpoint/index.rst | 1 +
Documentation/PCI/endpoint/pci-ntb-howto.rst | 160 +++++++++++++++++++
2 files changed, 161 insertions(+)
create mode 100644 Documentation/PCI/endpoint/pci-ntb-howto.rst

diff --git a/Documentation/PCI/endpoint/index.rst b/Documentation/PCI/endpoint/index.rst
index 9cb6e5f3c4d5..38ea1f604b6d 100644
--- a/Documentation/PCI/endpoint/index.rst
+++ b/Documentation/PCI/endpoint/index.rst
@@ -12,6 +12,7 @@ PCI Endpoint Framework
pci-test-function
pci-test-howto
pci-ntb-function
+ pci-ntb-howto

function/binding/pci-test
function/binding/pci-ntb
diff --git a/Documentation/PCI/endpoint/pci-ntb-howto.rst b/Documentation/PCI/endpoint/pci-ntb-howto.rst
new file mode 100644
index 000000000000..b6e1073c9a39
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-ntb-howto.rst
@@ -0,0 +1,160 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+PCI Non-Transparent Bridge (NTB) Endpoint Function (EPF) User Guide
+===================================================================
+
+:Author: Kishon Vijay Abraham I <kishon@xxxxxx>
+
+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
+Documentation/PCI/endpoint/pci-ntb-function.rst
+
+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
+
+If PCI_ENDPOINT_CONFIGFS is enabled::
+
+ # 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
+
+If PCI_ENDPOINT_CONFIGFS is enabled::
+
+ # 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
+ 0xffff
+ # cat functions/pci_epf_ntb/func1/interrupt_pin
+ 0x0001
+
+
+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
+ spad_count
+
+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 PCIe endpoint controllers
+connected to the two hosts. Use the 'primary' and 'secondary' entries
+inside NTB function device to attach one PCIe endpoint controller to
+primary interface and the other PCIe endpoint controller to the secondary
+interface. ::
+
+ # 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 PCIe 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>`
--
2.17.1