From: Stuart Yoder <stuart.yoder@freescale.com>
To: <gregkh@linuxfoundation.org>, <german.rivera@freescale.com>,
        <itai.katz@freescale.com>
CC: <devel@driverdev.osuosl.org>, <linux-kernel@vger.kernel.org>,
        <agraf@suse.de>, <arnd@arndb.de>,
        Stuart Yoder <stuart.yoder@freescale.com>
Subject: [PATCH v2] staging: fsl-mc: add DPAA2 overview readme
Date: Thu, 6 Aug 2015 20:09:24 -0500
Message-ID: <1438909764-16338-1-git-send-email-stuart.yoder@freescale.com>
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add README file providing an overview of the DPAA2 architecture
and how it is integrated in Linux

Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
---
-v2: added changelog text

 drivers/staging/fsl-mc/README.txt | 364 ++++++++++++++++++++++++++++++++++++++
 drivers/staging/fsl-mc/TODO       |   4 -
 2 files changed, 364 insertions(+), 4 deletions(-)
 create mode 100644 drivers/staging/fsl-mc/README.txt

diff --git a/drivers/staging/fsl-mc/README.txt b/drivers/staging/fsl-mc/README.txt
new file mode 100644
index 0000000..8214102
--- /dev/null
+++ b/drivers/staging/fsl-mc/README.txt
@@ -0,0 +1,364 @@
+Copyright (C) 2015 Freescale Semiconductor Inc.
+
+DPAA2 (Data Path Acceleration Architecture Gen2)
+------------------------------------------------
+
+This document provides an overview of the Freescale DPAA2 architecture
+and how it is integrated into the Linux kernel.
+
+Contents summary
+   -DPAA2 overview
+   -Overview of DPAA2 objects
+   -DPAA2 Linux driver architecture overview
+        -bus driver
+        -dprc driver
+        -allocator
+        -dpio driver
+        -Ethernet
+        -mac
+
+DPAA2 Overview
+--------------
+
+DPAA2 is a hardware architecture designed for high-speeed network
+packet processing.  DPAA2 consists of sophisticated mechanisms for
+processing Ethernet packets, queue management, buffer management,
+autonomous L2 switching, virtual Ethernet bridging, and accelerator
+(e.g. crypto) sharing.
+
+A DPAA2 hardware component called the Management Complex (or MC) manages the
+DPAA2 hardware resources.  The MC provides an object-based abstraction for
+software drivers to use the DPAA2 hardware.
+
+The MC uses DPAA2 hardware resources such as queues, buffer pools, and
+network ports to create functional objects/devices such as network
+interfaces, an L2 switch, or accelerator instances.
+
+The MC provides memory-mapped I/O command interfaces (MC portals)
+which DPAA2 software drivers use to operate on DPAA2 objects:
+
+         +--------------------------------------+
+         |                  OS                  |
+         |                        DPAA2 drivers |
+         |                             |        |
+         +-----------------------------|--------+
+                                       |
+                                       | (create,discover,connect
+                                       |  config,use,destroy)
+                                       |
+                         DPAA2         |
+         +------------------------| mc portal |-+
+         |                             |        |
+         |   +- - - - - - - - - - - - -V- - -+  |
+         |   |                               |  |
+         |   |   Management Complex (MC)     |  |
+         |   |                               |  |
+         |   +- - - - - - - - - - - - - - - -+  |
+         |                                      |
+         | Hardware                  Hardware   |
+         | Resources                 Objects    |
+         | ---------                 -------    |
+         | -queues                   -DPRC      |
+         | -buffer pools             -DPMCP     |
+         | -Eth MACs/ports           -DPIO      |
+         | -network interface        -DPNI      |
+         |  profiles                 -DPMAC     |
+         | -queue portals            -DPBP      |
+         | -MC portals                ...       |
+         |  ...                                 |
+         |                                      |
+         +--------------------------------------+
+
+The MC mediates operations such as create, discover,
+connect, configuration, and destroy.  Fast-path operations
+on data, such as packet transmit/receive, are not mediated by
+the MC and are done directly using memory mapped regions in
+DPIO objects.
+
+Overview of DPAA2 Objects
+-------------------------
+The section provides a brief overview of some key objects
+in the DPAA2 hardware.  A simple scenario is described illustrating
+the objects involved in creating a network interfaces.
+
+-DPRC (Datapath Resource Container)
+
+    A DPRC is an container object that holds all the other
+    types of DPAA2 objects.  In the example diagram below there
+    are 8 objects of 5 types (DPMCP, DPIO, DPBP, DPNI, and DPMAC)
+    in the container.
+
+    +---------------------------------------------------------+
+    | DPRC                                                    |
+    |                                                         |
+    |  +-------+  +-------+  +-------+  +-------+  +-------+  |
+    |  | DPMCP |  | DPIO  |  | DPBP  |  | DPNI  |  | DPMAC |  |
+    |  +-------+  +-------+  +-------+  +---+---+  +---+---+  |
+    |  | DPMCP |  | DPIO  |                                   |
+    |  +-------+  +-------+                                   |
+    |  | DPMCP |                                              |
+    |  +-------+                                              |
+    |                                                         |
+    +---------------------------------------------------------+
+
+    From the point of view of an OS, a DPRC is bus-like.  Like
+    a plug-and-play bus, such as PCI, DPRC commands can be used to
+    enumerate the contents of the DPRC, discover the hardware
+    objects present (including mappable regions and interrupts).
+
+     dprc.1 (bus)
+       |
+       +--+--------+-------+-------+-------+
+          |        |       |       |       |
+        dpmcp.1  dpio.1  dpbp.1  dpni.1  dpmac.1
+        dpmcp.2  dpio.2
+        dpmcp.3
+
+    Hardware objects can be created and destroyed dynamically, providing
+    the ability to hot plug/unplug objects in and out of the DPRC.
+
+    A DPRC has a mappable mmio region (an MC portal) that can be used
+    to send MC commands.  It has an interrupt for status events (like
+    hotplug).
+
+    All objects in a container share the same hardware "isolation context".
+    This means that with respect to an IOMMU the isolation granularity
+    is at the DPRC (container) level, not at the individual object
+    level.
+
+    DPRCs can be defined statically and populated with objects
+    via a config file passed to the MC when firmware starts
+    it.  There is also a Linux user space tool called "restool"
+    that can be used to create/destroy containers and objects
+    dynamically.
+
+-DPAA2 Objects for an Ethernet Network Interface
+
+    A typical Ethernet NIC is monolithic-- the NIC device contains TX/RX
+    queuing mechanisms, configuration mechanisms, buffer management,
+    physical ports, and interrupts.  DPAA2 uses a more granular approach
+    utilizing multiple hardware objects.  Each object has specialized
+    functions, and are used together by software to provide Ethernet network
+    interface functionality.  This approach provides efficient use of finite
+    hardware resources, flexibility, and performance advantages.
+
+    The diagram below shows the objects needed for a simple
+    network interface configuration on a system with 2 CPUs.
+
+              +---+---+ +---+---+
+                 CPU0     CPU1
+              +---+---+ +---+---+
+                  |         |
+              +---+---+ +---+---+
+                 DPIO     DPIO
+              +---+---+ +---+---+
+                    \     /
+                     \   /
+                      \ /
+                   +---+---+
+                      DPNI  --- DPBP,DPMCP
+                   +---+---+
+                       |
+                       |
+                   +---+---+
+                     DPMAC
+                   +---+---+
+                       |
+                    port/PHY
+
+    Below the objects are described.  For each object a brief description
+    is provided along with a summary of the kinds of operations the object
+    supports and a summary of key resources of the object (mmio regions
+    and irqs).
+
+       -DPMAC (Datapath Ethernet MAC): represents an Ethernet MAC, a
+        hardware device that connects to an Ethernet PHY and allows
+        physical transmission and reception of Ethernet frames.
+           -mmio regions: none
+           -irqs: dpni link change
+           -commands: set link up/down, link config, get stats,
+             irq config, enable, reset
+
+       -DPNI (Datapath Network Interface): contains TX/RX queues,
+        network interface configuration, and rx buffer pool configuration
+        mechanisms.
+           -mmio regions: none
+           -irqs: link state
+           -commands: port config, offload config, queue config,
+            parse/classify config, irq config, enable, reset
+
+       -DPIO (Datapath I/O): provides interfaces to enqueue and dequeue
+        packets and do hardware buffer pool management operations.  For
+        optimum performance there is typically DPIO per CPU.  This allows
+        each CPU to perform simultaneous enqueue/dequeue operations.
+           -mmio regions: queue operations, buffer mgmt
+           -irqs: data availability, congestion notification, buffer
+                  pool depletion
+           -commands: irq config, enable, reset
+
+       -DPBP (Datapath Buffer Pool): represents a hardware buffer
+        pool.
+           -mmio regions: none
+           -irqs: none
+           -commands: enable, reset
+
+       -DPMCP (Datapath MC Portal): provides an MC command portal.
+        Used by drivers to send commands to the MC to manage
+        objects.
+           -mmio regions: MC command portal
+           -irqs: command completion
+           -commands: irq config, enable, reset
+
+    Object Connections
+    ------------------
+    Some objects have explicit relationships that must
+    be configured:
+
+       -DPNI <--> DPMAC
+       -DPNI <--> DPNI
+       -DPNI <--> L2-switch-port
+          A DPNI must be connected to something such as a DPMAC,
+          another DPNI, or L2 switch port.  The DPNI connection
+          is made via a DPRC command.
+
+              +-------+  +-------+
+              | DPNI  |  | DPMAC |
+              +---+---+  +---+---+
+                  |          |
+                  +==========+
+
+       -DPNI <--> DPBP
+          A network interface requires a 'buffer pool' (DPBP
+          object) which provides a list of pointers to memory
+          where received Ethernet data is to be copied.  The
+          Ethernet driver configures the DPBPs associated with
+          the network interface.
+
+    Interrupts
+    ----------
+    All interrupts generated by DPAA2 objects are message
+    interrupts.  At the hardware level message interrupts
+    generated by devices will normally have 3 components--
+    1) a non-spoofable 'device-id' expressed on the hardware
+    bus, 2) an address, 3) a data value.
+
+    In the case of DPAA2 devices/objects, all objects in the
+    same container/DPRC share the same 'device-id'.
+    For ARM-based SoC this is the same as the stream ID.
+
+
+DPAA2 Linux Driver Overview
+---------------------------
+
+This section provides an overview of the Linux kernel drivers for
+DPAA2-- 1) the bus driver and associated "DPAA2 infrastructure"
+drivers and 2) functional object drivers (such as Ethernet).
+
+As described previously, a DPRC is a container that holds the other
+types of DPAA2 objects.  It is functionally similar to a plug-and-play
+bus controller.
+
+Each object in the DPRC is a Linux "device" and is bound to a driver.
+The diagram below shows the Linux drivers involved in a networking
+scenario and the objects bound to each driver.  A brief description
+of each driver follows.
+
+                                             +------------+
+                                             | OS Network |
+                                             |   Stack    |
+                 +------------+              +------------+
+                 | Allocator  |. . . . . . . |  Ethernet  |
+                 |(dpmcp,dpbp)|              |   (dpni)   |
+                 +-.----------+              +---+---+----+
+                  .          .                   ^   |
+                 .            .     <data avail, |   |<enqueue,
+                .              .     tx confirm> |   | dequeue>
+    +-------------+             .                |   |
+    | DPRC driver |              .           +---+---V----+     +---------+
+    |   (dprc)    |               . . . . . .| DPIO driver|     |   MAC   |
+    +----------+--+                          |  (dpio)    |     | (dpmac) |
+               |                             +------+-----+     +-----+---+
+               |<dev add/remove>                    |                 |
+               |                                    |                 |
+          +----+--------------+                     |              +--+---+
+          |   mc-bus driver   |                     |              | PHY  |
+          |                   |                     |              |driver|
+          | /fsl-mc@80c000000 |                     |              +--+---+
+          +-------------------+                     |                 |
+                                                    |                 |
+ ================================ HARDWARE =========|=================|======
+                                                  DPIO                |
+                                                    |                 |
+                                                  DPNI---DPBP         |
+                                                    |                 |
+                                                  DPMAC               |
+                                                    |                 |
+                                                   PHY ---------------+
+ ===================================================|========================
+
+A brief description of each driver is provided below.
+
+    mc-bus driver
+    -------------
+    The mc-bus driver is a platform driver and is probed from an
+    "/fsl-mc@xxxx" node in the device tree passed in by boot firmware.
+    It is responsible for bootstrapping the DPAA2 kernel infrastructure.
+    Key functions include:
+       -registering a new bus type named "fsl-mc" with the kernel,
+        and implementing bus call-backs (e.g. match/uevent/dev_groups)
+       -implemeting APIs for DPAA2 driver registration and for device
+        add/remove
+       -creates an MSI irq domain
+       -do a device add of the 'root' DPRC device, which is needed
+        to bootstrap things
+
+    DPRC driver
+    -----------
+    The dprc-driver is bound DPRC objects and does runtime management
+    of a bus instance.  It performs the initial bus scan of the DPRC
+    and handles interrupts for container events such as hot plug.
+
+    Allocator
+    ----------
+    Certain objects such as DPMCP and DPBP are generic and fungible,
+    and are intended to be used by other drivers.  For example,
+    the DPAA2 Ethernet driver needs:
+       -DPMCPs to send MC commands, to configure network interfaces
+       -DPBPs for network buffer pools
+
+    The allocator driver registers for these allocatable object types
+    and those objects are bound to the allocator when the bus is probed.
+    The allocator maintains a pool of objects that are available for
+    allocation by other DPAA2 drivers.
+
+    DPIO driver
+    -----------
+    The DPIO driver is bound to DPIO objects and provides services that allow
+    other drivers such as the Ethernet driver to receive and transmit data.
+    Key services include:
+        -data availability notifications
+        -hardware queuing operations (enqueue and dequeue of data)
+        -hardware buffer pool management
+
+    There is typically one DPIO object per physical CPU for optimum
+    performance, allowing each CPU to simultaneously enqueue
+    and dequeue data.
+
+    The DPIO driver operates on behalf of all DPAA2 drivers
+    active in the kernel--  Ethernet, crypto, compression,
+    etc.
+
+    Ethernet
+    --------
+    The Ethernet driver is bound to a DPNI and implements the kernel
+    interfaces needed to connect the DPAA2 network interface to
+    the network stack.
+
+    Each DPNI corresponds to a Linux network interface.
+
+    MAC driver
+    ----------
+    An Ethernet PHY is an off-chip, board specific component and is managed
+    by the appropriate PHY driver via an mdio bus.  The MAC driver
+    plays a role of being a proxy between the PHY driver and the
+    MC.  It does this proxy via the MC commands to a DPMAC object.
diff --git a/drivers/staging/fsl-mc/TODO b/drivers/staging/fsl-mc/TODO
index c29516b..3894368 100644
--- a/drivers/staging/fsl-mc/TODO
+++ b/drivers/staging/fsl-mc/TODO
@@ -1,7 +1,3 @@
-* Add README file (with ASCII art) describing relationships between
-  DPAA2 objects and how combine them to make a NIC, an LS2 switch, etc.
-  Also, define all acronyms used.
-
 * Decide if multiple root fsl-mc buses will be supported per Linux instance,
   and if so add support for this.
 
-- 
2.3.3

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