[PATCH v2] staging: fsl-mc: add DPAA2 overview readme
From: Stuart Yoder
Date: Thu Aug 06 2015 - 21:21:33 EST
add README file providing an overview of the DPAA2 architecture
and how it is integrated in Linux
Signed-off-by: Stuart Yoder <stuart.yoder@xxxxxxxxxxxxx>
---
-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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