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Subject: [PATCH Xilinx Alveo 1/8] Documentation: fpga: Add a document describing Alveo XRT drivers
Date:   Sat, 28 Nov 2020 16:00:33 -0800
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From: Sonal Santan <sonal.santan@xilinx.com>

Describe Alveo XRT driver architecture and provide basic overview
of Xilinx Alveo platform.

Signed-off-by: Sonal Santan <sonal.santan@xilinx.com>
---
 Documentation/fpga/index.rst |   1 +
 Documentation/fpga/xrt.rst   | 588 +++++++++++++++++++++++++++++++++++
 2 files changed, 589 insertions(+)
 create mode 100644 Documentation/fpga/xrt.rst

diff --git a/Documentation/fpga/index.rst b/Documentation/fpga/index.rst
index f80f95667ca2..30134357b70d 100644
--- a/Documentation/fpga/index.rst
+++ b/Documentation/fpga/index.rst
@@ -8,6 +8,7 @@ fpga
     :maxdepth: 1

     dfl
+    xrt

 .. only::  subproject and html

diff --git a/Documentation/fpga/xrt.rst b/Documentation/fpga/xrt.rst
new file mode 100644
index 000000000000..9f37d46459b0
--- /dev/null
+++ b/Documentation/fpga/xrt.rst
@@ -0,1 +1,588 @@
+==================================
+XRTV2 Linux Kernel Driver Overview
+==================================
+
+XRTV2 drivers are second generation `XRT <https://github.com/Xilinx/XRT>`_ drivers which
+support `Alveo <https://www.xilinx.com/products/boards-and-kits/alveo.html>`_ PCIe platforms
+from Xilinx.
+
+XRTV2 drivers support *subsystem* style data driven platforms where driver's configuration
+and behavior is determined by meta data provided by platform (in *device tree* format).
+Primary management physical function (MPF) driver is called **xmgmt**. Primary user physical
+function (UPF) driver is called **xuser** and HW subsystem drivers are packaged into a library
+module called **xrt-lib**, which is shared by **xmgmt** and **xuser** (WIP).
+
+Alveo Platform Overview
+=======================
+
+Alveo platforms are architected as two physical FPGA partitions: *Shell* and *User*. Shell
+provides basic infrastructure for the Alveo platform like PCIe connectivity, board management,
+Dynamic Function Exchange (DFX), sensors, clocking, reset, and security. User partition contains
+user compiled binary which is loaded by a process called DFX also known as partial reconfiguration.
+
+Physical partitions require strict HW compatibility with each other for DFX to work properly.
+Every physical partition has two interface UUIDs: *parent* UUID and *child* UUID. For simple
+single stage platforms Shell → User forms parent child relationship. For complex two stage
+platforms Base → Shell → User forms the parent child relationship chain.
+
+.. note::
+   Partition compatibility matching is key design component of Alveo platforms and XRT. Partitions
+   have child and parent relationship. A loaded partition exposes child partition UUID to advertise
+   its compatibility requirement for child partition. When loading a child partition the xmgmt
+   management driver matches parent UUID of the child partition against child UUID exported by the
+   parent. Parent and child partition UUIDs are stored in the *xclbin* (for user) or *xsabin* (for
+   base and shell). Except for root UUID, VSEC, hardware itself does not know about UUIDs. UUIDs are
+   stored in xsabin and xclbin.
+
+
+The physical partitions and their loading is illustrated below::
+
+            SHELL                               USER
+        +-----------+                  +-------------------+
+        |           |                  |                   |
+        | VSEC UUID | CHILD     PARENT |    LOGIC UUID     |
+        |           o------->|<--------o                   |
+        |           | UUID       UUID  |                   |
+        +-----+-----+                  +--------+----------+
+              |                                 |
+              .                                 .
+              |                                 |
+          +---+---+                      +------+--------+
+          |  POR  |                      | USER COMPILED |
+          | FLASH |                      |    XCLBIN     |
+          +-------+                      +---------------+
+
+
+Loading Sequence
+----------------
+
+Shell partition is loaded from flash at system boot time. It establishes the PCIe link and exposes
+two physical functions to the BIOS. After OS boot, xmgmt driver attaches to PCIe physical function
+0 exposed by the Shell and then looks for VSEC in PCIe extended configuration space. Using VSEC it
+determines the logic UUID of Shell and uses the UUID to load matching *xsabin* file from Linux
+firmware directory. The xsabin file contains metadata to discover peripherals that are part of Shell
+and firmware(s) for any embedded soft processors in Shell.
+
+Shell exports child interface UUID which is used for compatibility check when loading user compiled
+xclbin over the User partition as part of DFX. When a user requests loading of a specific xclbin the
+xmgmt management driver reads the parent interface UUID specified in the xclbin and matches it with
+child interface UUID exported by Shell to determine if xclbin is compatible with the Shell. If match
+fails loading of xclbin is denied.
+
+xclbin loading is requested using ICAP_DOWNLOAD_AXLF ioctl command. When loading xclbin xmgmt driver
+performs the following operations:
+
+1. Sanity check the xclbin contents
+2. Isolate the User partition
+3. Download the bitstream using the FPGA config engine (ICAP)
+4. De-isolate the User partition
+5. Program the clocks (ClockWiz) driving the User partition
+6. Wait for memory controller (MIG) calibration
+
+`Platform Loading Overview <https://xilinx.github.io/XRT/master/html/platforms_partitions.html>`_
+provides more detailed information on platform loading.
+
+xsabin
+------
+
+Each Alveo platform comes packaged with its own xsabin. The xsabin is trusted component of the
+platform. For format details refer to :ref:`xsabin/xclbin Container Format`. xsabin contains
+basic information like UUIDs, platform name and metadata in the form of device tree. See
+:ref:`Device Tree Usage` for details and example.
+
+xclbin
+------
+
+xclbin is compiled by end user using
+`Vitis <https://www.xilinx.com/products/design-tools/vitis/vitis-platform.html>`_ tool set from
+Xilinx. The xclbin contains sections describing user compiled acceleration engines/kernels, memory
+subsystems, clocking information etc. It also contains bitstream for the user partition, UUIDs,
+platform name, etc. xclbin uses the same container format as xsabin which is described below.
+
+
+xsabin/xclbin Container Format
+------------------------------
+
+xclbin/xsabin is ELF-like binary container format. It is structured as series of sections.
+There is a file header followed by several section headers which is followed by sections.
+A section header points to an actual section. There is an optional signature at the end.
+The format is defined by header file ``xclbin.h``. The following figure illustrates a
+typical xclbin::
+
+
+          +---------------------+
+          |                     |
+          |       HEADER        |
+          +---------------------+
+          |   SECTION  HEADER   |
+          |                     |
+          +---------------------+
+          |         ...         |
+          |                     |
+          +---------------------+
+          |   SECTION  HEADER   |
+          |                     |
+          +---------------------+
+          |       SECTION       |
+          |                     |
+          +---------------------+
+          |         ...         |
+          |                     |
+          +---------------------+
+          |       SECTION       |
+          |                     |
+          +---------------------+
+          |      SIGNATURE      |
+          |      (OPTIONAL)     |
+          +---------------------+
+
+
+xclbin/xsabin files can be packaged, un-packaged and inspected using XRT utility called
+**xclbinutil**. xclbinutil is part of XRT open source software stack. The source code for
+xclbinutil can be found at https://github.com/Xilinx/XRT/tree/master/src/runtime_src/tools/xclbinutil
+
+For example to enumerate the contents of a xclbin/xsabin use the *--info* switch as shown
+below::
+
+  xclbinutil --info --input /opt/xilinx/firmware/u50/gen3x16-xdma/blp/test/bandwidth.xclbin
+  xclbinutil --info --input /lib/firmware/xilinx/862c7020a250293e32036f19956669e5/partition.xsabin
+
+
+Device Tree Usage
+-----------------
+
+As mentioned previously xsabin stores metadata which advertise HW subsystems present in a partition.
+The metadata is stored in device tree format with well defined schema. Subsystem instantiations are
+captured as children of ``addressable_endpoints`` node. Subsystem nodes have standard attributes like
+``reg``, ``interrupts`` etc. Additionally the nodes also have PCIe specific attributes:
+``pcie_physical_function`` and ``pcie_bar_mapping``. These identify which PCIe physical function and
+which BAR space in that physical function the subsystem resides. XRT management driver uses this
+information to bind *platform drivers* to the subsystem instantiations. The platform drivers are
+found in **xrt-lib.ko** kernel module defined later. Below is an example of device tree for Alveo U50
+platform::
+
+  /dts-v1/;
+
+  /{
+	logic_uuid = "f465b0a3ae8c64f619bc150384ace69b";
+
+	schema_version {
+		major = <0x01>;
+		minor = <0x00>;
+	};
+
+	interfaces {
+
+		@0 {
+			interface_uuid = "862c7020a250293e32036f19956669e5";
+		};
+	};
+
+	addressable_endpoints {
+
+		ep_blp_rom_00 {
+			reg = <0x00 0x1f04000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_bram_ctrl-1.0\0axi_bram_ctrl";
+		};
+
+		ep_card_flash_program_00 {
+			reg = <0x00 0x1f06000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_quad_spi-1.0\0axi_quad_spi";
+			interrupts = <0x03 0x03>;
+		};
+
+		ep_cmc_firmware_mem_00 {
+			reg = <0x00 0x1e20000 0x00 0x20000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_bram_ctrl-1.0\0axi_bram_ctrl";
+
+			firmware {
+				firmware_product_name = "cmc";
+				firmware_branch_name = "u50";
+				firmware_version_major = <0x01>;
+				firmware_version_minor = <0x00>;
+			};
+		};
+
+		ep_cmc_intc_00 {
+			reg = <0x00 0x1e03000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_intc-1.0\0axi_intc";
+			interrupts = <0x04 0x04>;
+		};
+
+		ep_cmc_mutex_00 {
+			reg = <0x00 0x1e02000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_cmc_regmap_00 {
+			reg = <0x00 0x1e08000 0x00 0x2000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_bram_ctrl-1.0\0axi_bram_ctrl";
+
+			firmware {
+				firmware_product_name = "sc-fw";
+				firmware_branch_name = "u50";
+				firmware_version_major = <0x05>;
+			};
+		};
+
+		ep_cmc_reset_00 {
+			reg = <0x00 0x1e01000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_ddr_mem_calib_00 {
+			reg = <0x00 0x63000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_debug_bscan_mgmt_00 {
+			reg = <0x00 0x1e90000 0x00 0x10000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-debug_bridge-1.0\0debug_bridge";
+		};
+
+		ep_ert_base_address_00 {
+			reg = <0x00 0x21000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_ert_command_queue_mgmt_00 {
+			reg = <0x00 0x40000 0x00 0x10000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-ert_command_queue-1.0\0ert_command_queue";
+		};
+
+		ep_ert_command_queue_user_00 {
+			reg = <0x00 0x40000 0x00 0x10000>;
+			pcie_physical_function = <0x01>;
+			compatible = "xilinx.com,reg_abs-ert_command_queue-1.0\0ert_command_queue";
+		};
+
+		ep_ert_firmware_mem_00 {
+			reg = <0x00 0x30000 0x00 0x8000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_bram_ctrl-1.0\0axi_bram_ctrl";
+
+			firmware {
+				firmware_product_name = "ert";
+				firmware_branch_name = "v20";
+				firmware_version_major = <0x01>;
+			};
+		};
+
+		ep_ert_intc_00 {
+			reg = <0x00 0x23000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_intc-1.0\0axi_intc";
+			interrupts = <0x05 0x05>;
+		};
+
+		ep_ert_reset_00 {
+			reg = <0x00 0x22000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_ert_sched_00 {
+			reg = <0x00 0x50000 0x00 0x1000>;
+			pcie_physical_function = <0x01>;
+			compatible = "xilinx.com,reg_abs-ert_sched-1.0\0ert_sched";
+			interrupts = <0x09 0x0c>;
+		};
+
+		ep_fpga_configuration_00 {
+			reg = <0x00 0x1e88000 0x00 0x8000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_hwicap-1.0\0axi_hwicap";
+			interrupts = <0x02 0x02>;
+		};
+
+		ep_icap_reset_00 {
+			reg = <0x00 0x1f07000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_mailbox_mgmt_00 {
+			reg = <0x00 0x1f10000 0x00 0x10000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-mailbox-1.0\0mailbox";
+			interrupts = <0x00 0x00>;
+		};
+
+		ep_mailbox_user_00 {
+			reg = <0x00 0x1f00000 0x00 0x10000>;
+			pcie_physical_function = <0x01>;
+			compatible = "xilinx.com,reg_abs-mailbox-1.0\0mailbox";
+			interrupts = <0x08 0x08>;
+		};
+
+		ep_msix_00 {
+			reg = <0x00 0x00 0x00 0x20000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-msix-1.0\0msix";
+			pcie_bar_mapping = <0x02>;
+		};
+
+		ep_pcie_link_mon_00 {
+			reg = <0x00 0x1f05000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_pr_isolate_plp_00 {
+			reg = <0x00 0x1f01000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_pr_isolate_ulp_00 {
+			reg = <0x00 0x1000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_gpio-1.0\0axi_gpio";
+		};
+
+		ep_uuid_rom_00 {
+			reg = <0x00 0x64000 0x00 0x1000>;
+			pcie_physical_function = <0x00>;
+			compatible = "xilinx.com,reg_abs-axi_bram_ctrl-1.0\0axi_bram_ctrl";
+		};
+
+		ep_xdma_00 {
+			reg = <0x00 0x00 0x00 0x10000>;
+			pcie_physical_function = <0x01>;
+			compatible = "xilinx.com,reg_abs-xdma-1.0\0xdma";
+			pcie_bar_mapping = <0x02>;
+		};
+	};
+
+  }
+
+
+
+Deployment Models
+=================
+
+Baremetal
+---------
+
+In bare-metal deployments both MPF and UPF are visible and accessible. xmgmt driver binds to
+MPF. xmgmt driver operations are privileged and available to system administrator. The full
+stack is illustrated below::
+
+
+                            HOST
+
+                 [XMGMT]            [XUSER]
+                    |                  |
+                    |                  |
+                 +-----+            +-----+
+                 | MPF |            | UPF |
+                 |     |            |     |
+                 | PF0 |            | PF1 |
+                 +--+--+            +--+--+
+          ......... ^................. ^..........
+                    |                  |
+                    |   PCIe DEVICE    |
+                    |                  |
+                 +--+------------------+--+
+                 |         SHELL          |
+                 |                        |
+                 +------------------------+
+                 |         USER           |
+                 |                        |
+                 |                        |
+                 |                        |
+                 |                        |
+                 +------------------------+
+
+
+
+Virtualized
+-----------
+
+In virtualized deployments privileged MPF is assigned to host but unprivileged UPF
+is assigned to guest VM via PCIe pass-through. xmgmt driver in host binds to MPF.
+xmgmt driver operations are privileged and only accessible by hosting service provider.
+The full stack is illustrated below::
+
+
+                                 .............
+                  HOST           .    VM     .
+                                 .           .
+                 [XMGMT]         .  [XUSER]  .
+                    |            .     |     .
+                    |            .     |     .
+                 +-----+         .  +-----+  .
+                 | MPF |         .  | UPF |  .
+                 |     |         .  |     |  .
+                 | PF0 |         .  | PF1 |  .
+                 +--+--+         .  +--+--+  .
+          ......... ^................. ^..........
+                    |                  |
+                    |   PCIe DEVICE    |
+                    |                  |
+                 +--+------------------+--+
+                 |         SHELL          |
+                 |                        |
+                 +------------------------+
+                 |         USER           |
+                 |                        |
+                 |                        |
+                 |                        |
+                 |                        |
+                 +------------------------+
+
+
+
+Driver Modules
+==============
+
+xrt-lib.ko
+----------
+
+Repository of all subsystem drivers and pure software modules that can potentially
+be shared between xmgmt and xuser. All these drivers are structured as Linux
+*platform driver* and are instantiated by xmgmt (or xuser in future) based on meta
+data associated with hardware. The metadata is in the form of device tree as
+explained before.
+
+xmgmt.ko
+--------
+
+The xmgmt driver is a PCIe device driver driving MPF found on Xilinx's Alveo
+PCIE device. It consists of one *root* driver, one or more *partition* drivers
+and one or more *leaf* drivers. The root and MPF specific leaf drivers are in
+xmgmt.ko. The partition driver and other leaf drivers are in xrt-lib.ko.
+
+The instantiation of specific partition driver or leaf driver is completely data
+driven based on meta data (mostly in device tree format) found through VSEC
+capability and inside firmware files, such as xsabin or xclbin file. The root
+driver manages life cycle of multiple partition drivers, which, in turn, manages
+multiple leaf drivers. This allows a single set of driver code to support all
+kinds of subsystems exposed by different shells. The difference among all
+these subsystems will be handled in leaf drivers with root and partition drivers
+being part of the infrastructure and provide common services for all leaves found
+on all platforms.
+
+
+xmgmt-root
+^^^^^^^^^^
+
+The xmgmt-root driver is a PCIe device driver attaches to MPF. It's part of the
+infrastructure of the MPF driver and resides in xmgmt.ko. This driver
+
+* manages one or more partition drivers
+* provides access to functionalities that requires pci_dev, such as PCIE config
+  space access, to other leaf drivers through parent calls
+* together with partition driver, facilities event callbacks for other leaf drivers
+* together with partition driver, facilities inter-leaf driver calls for other leaf
+  drivers
+
+When root driver starts, it will explicitly create an initial partition instance,
+which contains leaf drivers that will trigger the creation of other partition
+instances. The root driver will wait for all partitions and leaves to be created
+before it returns from it's probe routine and claim success of the initialization
+of the entire xmgmt driver.
+
+partition
+^^^^^^^^^
+
+The partition driver is a platform device driver whose life cycle is managed by
+root and does not have real IO mem or IRQ resources. It's part of the
+infrastructure of the MPF driver and resides in xrt-lib.ko. This driver
+
+* manages one or more leaf drivers so that multiple leaves can be managed as a group
+* provides access to root from leaves, so that parent calls, event notifications
+  and inter-leaf calls can happen
+
+In xmgmt, an initial partition driver instance will be created by root, which
+contains leaves that will trigger partition instances to be created to manage
+groups of leaves found on different partitions on hardware, such as VSEC, Shell,
+and User.
+
+leaves
+^^^^^^
+
+The leaf driver is a platform device driver whose life cycle is managed by
+a partition driver and may or may not have real IO mem or IRQ resources. They
+are the real meat of xmgmt and contains platform specific code to Shell and User
+found on a MPF.
+
+A leaf driver may not have real hardware resources when it merely acts as a driver
+that manages certain in-memory states for xmgmt. These in-memory states could be
+shared by multiple other leaves.
+
+Leaf drivers assigned to specific hardware resources drive specific subsystem in
+the device. To manipulate the subsystem or carry out a task, a leaf driver may ask
+help from root via parent calls and/or from other leaves via inter-leaf calls.
+
+A leaf can also broadcast events through infrastructure code for other leaves
+to process. It can also receive event notification from infrastructure about certain
+events, such as post-creation or pre-exit of a particular leaf.
+
+
+Driver Interfaces
+=================
+
+xmgmt Driver Ioctls
+-------------------
+
+Ioctls exposed by xmgmt driver to user space are enumerated in the following table:
+
+== ===================== ============================= ===========================
+#  Functionality         ioctl request code            data format
+== ===================== ============================= ===========================
+1  FPGA image download   XMGMT_IOCICAPDOWNLOAD_AXLF    xmgmt_ioc_bitstream_axlf
+2  CL frequency scaling  XMGMT_IOCFREQSCALE            xmgmt_ioc_freqscaling
+== ===================== ============================= ===========================
+
+xmgmt Driver Sysfs
+------------------
+
+xmgmt driver exposes a rich set of sysfs interfaces. Subsystem platform drivers
+export sysfs node for every platform instance.
+
+Every partition also exports its UUIDs. See below for examples::
+
+  /sys/bus/pci/devices/0000:06:00.0/xmgmt_main.0/interface_uuids
+  /sys/bus/pci/devices/0000:06:00.0/xmgmt_main.0/logic_uuids
+
+
+hwmon
+-----
+
+xmgmt driver exposes standard hwmon interface to report voltage, current, temperature,
+power, etc. These can easily be viewed using *sensors* command line utility.
+
+
+mailbox
+-------
+
+xmgmt communicates with user physical function driver via HW mailbox. Mailbox opcodes
+are defined in ``mailbox_proto.h``. `Mailbox Inter-domain Communication Protocol
+<https://xilinx.github.io/XRT/master/html/mailbox.proto.html>`_ defines the full
+specification. xmgmt implements subset of the specification. It provides the following
+services to the UPF driver:
+
+1.  Responding to *are you there* request including determining if the two drivers are
+    running in the same OS domain
+2.  Provide sensor readings, loaded xclbin UUID, clock frequency, shell information, etc.
+3.  Perform PCIe hot reset
+4.  Download user compiled xclbin
+
+
+Platform Security Considerations
+================================
+
+`Security of Alveo Platform <https://xilinx.github.io/XRT/master/html/security.html>`_
+discusses the deployment options and security implications in great detail.
--
2.17.1