[PATCH v2 4/4] Documentation: PCI: Add specification for the PCI vNTB function device

[Frank Li <Frank.Li@nxp.com>]

Add specification for the PCI vNTB function device. The endpoint function
driver and the host PCI driver should be created based on this
specification.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Change from v1:
 - Add virtual pci ntb driver config

 Documentation/PCI/endpoint/index.rst          |   2 +
 .../PCI/endpoint/pci-vntb-function.rst        | 126 +++++++++++++
 Documentation/PCI/endpoint/pci-vntb-howto.rst | 167 ++++++++++++++++++
 3 files changed, 295 insertions(+)
 create mode 100644 Documentation/PCI/endpoint/pci-vntb-function.rst
 create mode 100644 Documentation/PCI/endpoint/pci-vntb-howto.rst

diff --git a/Documentation/PCI/endpoint/index.rst b/Documentation/PCI/endpoint/index.rst
index 38ea1f604b6d3..4d2333e7ae067 100644
--- a/Documentation/PCI/endpoint/index.rst
+++ b/Documentation/PCI/endpoint/index.rst
@@ -13,6 +13,8 @@ PCI Endpoint Framework
    pci-test-howto
    pci-ntb-function
    pci-ntb-howto
+   pci-vntb-function
+   pci-vntb-howto
 
    function/binding/pci-test
    function/binding/pci-ntb
diff --git a/Documentation/PCI/endpoint/pci-vntb-function.rst b/Documentation/PCI/endpoint/pci-vntb-function.rst
new file mode 100644
index 0000000000000..cad8013e88390
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-vntb-function.rst
@@ -0,0 +1,126 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+PCI vNTB Function
+=================
+
+:Author: Frank Li <Frank.Li@nxp.com>
+
+The difference between PCI NTB function and PCI vNTB function is
+
+PCI NTB function need at two endpoint instances and connect HOST1
+and HOST2.
+
+PCI vNTB function only use one host and one endpoint(EP), use NTB
+connect EP and PCI host
+
+.. code-block:: text
+
+
+  +------------+         +---------------------------------------+
+  |            |         |                                       |
+  +------------+         |                        +--------------+
+  | NTB        |         |                        | NTB          |
+  | NetDev     |         |                        | NetDev       |
+  +------------+         |                        +--------------+
+  | NTB        |         |                        | NTB          |
+  | Transfer   |         |                        | Transfer     |
+  +------------+         |                        +--------------+
+  |            |         |                        |              |
+  |  PCI NTB   |         |                        |              |
+  |    EPF     |         |                        |              |
+  |   Driver   |         |                        | PCI Virtual  |
+  |            |         +---------------+        | NTB Driver   |
+  |            |         | PCI EP NTB    |<------>|              |
+  |            |         |  FN Driver    |        |              |
+  +------------+         +---------------+        +--------------+
+  |            |         |               |        |              |
+  |  PCI BUS   | <-----> |  PCI EP BUS   |        |  Virtual PCI |
+  |            |  PCI    |               |        |     BUS      |
+  +------------+         +---------------+--------+--------------+
+      PCI RC                        PCI EP
+
+Constructs used for Implementing vNTB
+=====================================
+
+	1) Config Region
+	2) Self Scratchpad Registers
+	3) Peer Scratchpad Registers
+	4) Doorbell (DB) Registers
+	5) Memory Window (MW)
+
+
+Config Region:
+--------------
+
+It is same as PCI NTB Function driver
+
+Scratchpad Registers:
+---------------------
+
+  It is appended after Config region.
+
+  +--------------------------------------------------+ Base
+  |                                                  |
+  |                                                  |
+  |                                                  |
+  |          Common Config Register                  |
+  |                                                  |
+  |                                                  |
+  |                                                  |
+  +-----------------------+--------------------------+ Base + span_offset
+  |                       |                          |
+  |    Peer Span Space    |    Span Space            |
+  |                       |                          |
+  |                       |                          |
+  +-----------------------+--------------------------+ Base + span_offset
+  |                       |                          |      + span_count * 4
+  |                       |                          |
+  |     Span Space        |   Peer Span Space        |
+  |                       |                          |
+  +-----------------------+--------------------------+
+        Virtual PCI             Pcie Endpoint
+        NTB Driver               NTB Driver
+
+
+Doorbell Registers:
+-------------------
+
+  Doorbell Registers are used by the hosts to interrupt each other.
+
+Memory Window:
+--------------
+
+  Actual transfer of data between the two hosts will happen using the
+  memory window.
+
+Modeling Constructs:
+====================
+
+32-bit BARs.
+
+======  ===============
+BAR NO  CONSTRUCTS USED
+======  ===============
+BAR0    Config Region
+BAR1    Doorbell
+BAR2    Memory Window 1
+BAR3    Memory Window 2
+BAR4    Memory Window 3
+BAR5    Memory Window 4
+======  ===============
+
+64-bit BARs.
+
+======  ===============================
+BAR NO  CONSTRUCTS USED
+======  ===============================
+BAR0    Config Region + Scratchpad
+BAR1
+BAR2    Doorbell
+BAR3
+BAR4    Memory Window 1
+BAR5
+======  ===============================
+
+
diff --git a/Documentation/PCI/endpoint/pci-vntb-howto.rst b/Documentation/PCI/endpoint/pci-vntb-howto.rst
new file mode 100644
index 0000000000000..524cd487e1840
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-vntb-howto.rst
@@ -0,0 +1,167 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+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
+Documentation/PCI/endpoint/pci-vntb-function.rst
+
+Endpoint Device
+===============
+
+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
+
+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
+
+
+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-ntb 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_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-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
+
+
+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
+
+In order to configure NTB specific attributes, a new sub-directory to func1
+should be created::
+
+	# mkdir functions/pci_epf_vntb/func1/pci_epf_vntb.0/
+
+The NTB function driver will populate this directory with various attributes
+that can be configured by the user::
+
+	# ls functions/pci_epf_vntb/func1/pci_epf_vntb.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_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
+
+A sample configuration for virtual NTB driver for virutal 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
+
+Binding pci-epf-ntb 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-ntb/func1/primary
+
+Once the above step is completed, 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 (imx8 don't need this steps)::
+
+	# echo 1 > controllers/5f010000.pcie_ep/start
+
+RootComplex Device
+==================
+
+lspci Output at Host side
+------------------------
+
+Note that the devices listed here correspond to the values populated in
+"Creating pci-epf-ntb 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
+
+Endpoint Device / Virtual PCI bus
+=================================
+
+lspci Output at EP Side / Virtual PCI bus
+-----------------------------------------
+
+Note that the devices listed here correspond to the values populated in
+"Creating pci-epf-ntb Device" section above::
+
+        # lspci
+        10:00.0 Unassigned class [ffff]: Dawicontrol Computersysteme GmbH Device 1234 (rev ff)
+
+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>`
-- 
2.24.0.rc1