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