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Subject[PATCH 06/22] misc: xlink-pcie: Add documentation for XLink PCIe driver
Date
From: Srikanth Thokala <srikanth.thokala@intel.com>

Provide overview of XLink PCIe driver implementation

Cc: linux-doc@vger.kernel.org
Reviewed-by: Mark Gross <mgross@linux.intel.com>
Signed-off-by: Srikanth Thokala <srikanth.thokala@intel.com>
---
Documentation/vpu/index.rst | 1 +
Documentation/vpu/xlink-pcie.rst | 91 ++++++++++++++++++++++++++++++++
2 files changed, 92 insertions(+)
create mode 100644 Documentation/vpu/xlink-pcie.rst

diff --git a/Documentation/vpu/index.rst b/Documentation/vpu/index.rst
index 7e290e048910..661cc700ee45 100644
--- a/Documentation/vpu/index.rst
+++ b/Documentation/vpu/index.rst
@@ -14,3 +14,4 @@ This documentation contains information for the Intel VPU stack.
:maxdepth: 2

vpu-stack-overview
+ xlink-pcie
diff --git a/Documentation/vpu/xlink-pcie.rst b/Documentation/vpu/xlink-pcie.rst
new file mode 100644
index 000000000000..bc64b566989d
--- /dev/null
+++ b/Documentation/vpu/xlink-pcie.rst
@@ -0,0 +1,91 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver: xlink-pcie driver
+================================
+Supported chips:
+ * Intel Edge.AI Computer Vision platforms: Keem Bay
+ Suffix: Bay
+ Slave address: 6240
+ Datasheet: Publicly available at Intel
+
+Author: Srikanth Thokala Srikanth.Thokala@intel.com
+
+-------------
+Introduction:
+-------------
+The xlink-pcie driver in linux-5.4 provides transport layer implementation for
+the data transfers to support xlink protocol subsystem communication with the
+peer device. i.e, between remote host system and the local Keem Bay device.
+
+The Keem Bay device is an ARM based SOC that includes a vision processing
+unit (VPU) and deep learning, neural network core in the hardware.
+The xlink-pcie driver exports a functional device endpoint to the Keem Bay device
+and supports two-way communication with peer device.
+
+------------------------
+High-level architecture:
+------------------------
+Remote Host: IA CPU
+Local Host: ARM CPU (Keem Bay)::
+
+ +------------------------------------------------------------------------+
+ | Remote Host IA CPU | | Local Host ARM CPU (Keem Bay) | |
+ +==================================+=+===============================+===+
+ | User App | | User App | |
+ +----------------------------------+-+-------------------------------+---+
+ | XLink UAPI | | XLink UAPI | |
+ +----------------------------------+-+-------------------------------+---+
+ | XLink Core | | XLink Core | |
+ +----------------------------------+-+-------------------------------+---+
+ | XLink PCIe | | XLink PCIe | |
+ +----------------------------------+-+-------------------------------+---+
+ | XLink-PCIe Remote Host driver | | XLink-PCIe Local Host driver | |
+ +----------------------------------+-+-------------------------------+---+
+ |-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:|:|:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:|
+ +----------------------------------+-+-------------------------------+---+
+ | PCIe Host Controller | | PCIe Device Controller | HW|
+ +----------------------------------+-+-------------------------------+---+
+ ^ ^
+ | |
+ |------------- PCIe x2 Link -----------------|
+
+This XLink PCIe driver comprises of two variants:
+* Local Host driver
+
+ * Intended for ARM CPU
+ * It is based on PCI Endpoint Framework
+ * Driver path: {tree}/drivers/misc/xlink-pcie/local_host
+
+* Remote Host driver
+
+ * Intended for IA CPU
+ * It is a PCIe endpoint driver
+ * Driver path: {tree}/drivers/misc/xlink-pcie/remote_host
+
+XLink PCIe communication between local host and remote host is achieved through
+ring buffer management and MSI/Doorbell interrupts.
+
+The xlink-pcie driver subsystem registers Keem Bay device as an endpoint driver
+and provides standard linux pcie sysfs interface, # /sys/bus/pci/devices/xxxx:xx:xx.0/
+
+
+-------------------------
+XLink protocol subsystem:
+-------------------------
+xlink is an abstracted control and communication subsystem based on channel
+identification. It is intended to support VPU technology both at SoC level as
+well as at IP level, over multiple interfaces.
+
+- The xlink subsystem abstracts several types of communication channels
+ underneath, allowing the usage of different interfaces with the
+ same function call interface.
+- The Communication channels are full-duplex protocol channels allowing
+ concurrent bidirectional communication.
+- The xlink subsystem also supports control operations to VPU either
+ from standalone local system or from remote system based on communication
+ interface underneath.
+- The xlink subsystem supports following communication interfaces:
+ * USB CDC
+ * Gigabit Ethernet
+ * PCIe
+ * IPC
--
2.17.1
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