staging: fsl-mc: Convert documentation to rst format (60b91319) · Commits · e / devices / android_kernel_xiaomi_nabu

drivers/staging/fsl-mc/README.txt

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		Copyright (C) 2015 Freescale Semiconductor Inc.

		DPAA2 (Data Path Acceleration Architecture Gen2) Overview
		---------------------------------------------------------

		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

		Introduction
		------------

		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.

		The diagram below shows an overview of the DPAA2 resource management
		architecture:

		+--------------------------------------+
		\| 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 DPAA2 objects.
		A simple scenario is described illustrating the objects involved
		in creating a network interfaces.

		-DPRC (Datapath Resource Container)

		A DPRC is a 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 behaves similar to a plug and
		play bus, like 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.

		-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 provides specialized
		functions. Groups of these objects are used 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. The TX/RX queues are in memory and are identified by
		queue number.
		-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. The DPAA2
		architecture separates the mechanism to access queues (the DPIO object)
		from the queues themselves. The DPIO provides an MMIO interface to
		enqueue/dequeue packets. To enqueue something a descriptor is written
		to the DPIO MMIO region, which includes the target queue number.
		There will typically be one DPIO assigned to each CPU. This allows all
		CPUs to simultaneously perform enqueue/dequeued operations. DPIOs are
		expected to be shared by different DPAA2 drivers.
		-MMIO regions: queue operations, buffer management
		-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 Drivers 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\|
		\| /bus/fsl-mc \| \| +--+---+
		+-------------------+ \| \|
		\| \|
		================================ 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 a
		node in the device tree (compatible "fsl,qoriq-mc") 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)
		-implementing APIs for DPAA2 driver registration and for device
		add/remove
		-creates an MSI IRQ domain
		-doing a 'device add' to expose the 'root' DPRC, in turn triggering
		a bind of the root DPRC to the DPRC driver
		The binding for the MC-bus device-tree node can be consulted here:
		Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt
		The sysfs bind/unbind interfaces for the MC-bus can be consulted here:
		Documentation/ABI/testing/sysfs-bus-fsl-mc*

		DPRC driver
		-----------
		The DPRC driver is bound to 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 by
		re-scanning the DPRC.

		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 enqueue and dequeue data for
		their respective objects.
		Key services include:
		-data availability notifications
		-hardware queuing operations (enqueue and dequeue of data)
		-hardware buffer pool management

		To transmit a packet the Ethernet driver puts data on a queue and
		invokes a DPIO API. For receive, the Ethernet driver registers
		a data availability notification callback. To dequeue a packet
		a DPIO API is used.

		There is typically one DPIO object per physical CPU for optimum
		performance, allowing different CPUs 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 driver
		---------------
		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.
		If the PHY driver signals a link change, the MAC driver notifies
		the MC via a DPMAC command. If a network interface is brought
		up or down, the MC notifies the DPMAC driver via an interrupt and
		the driver can take appropriate action.

drivers/staging/fsl-mc/overview.rst

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