| 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: |
| |
| 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 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| |
| | /soc/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 |
| |
| 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 |
| -------- |
| 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. |
