[linux-2.6-block.git] / drivers / staging / fsl-mc / README.txt

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.
Commit	Line	Data
c9eda125 SY	1	Copyright (C) 2015 Freescale Semiconductor Inc.
	2
	3	DPAA2 (Data Path Acceleration Architecture Gen2)
	4	------------------------------------------------
	5
	6	This document provides an overview of the Freescale DPAA2 architecture
	7	and how it is integrated into the Linux kernel.
	8
	9	Contents summary
	10	-DPAA2 overview
	11	-Overview of DPAA2 objects
	12	-DPAA2 Linux driver architecture overview
	13	-bus driver
	14	-dprc driver
	15	-allocator
	16	-dpio driver
	17	-Ethernet
	18	-mac
	19
	20	DPAA2 Overview
	21	--------------
	22
	23	DPAA2 is a hardware architecture designed for high-speeed network
	24	packet processing. DPAA2 consists of sophisticated mechanisms for
	25	processing Ethernet packets, queue management, buffer management,
	26	autonomous L2 switching, virtual Ethernet bridging, and accelerator
	27	(e.g. crypto) sharing.
	28
	29	A DPAA2 hardware component called the Management Complex (or MC) manages the
	30	DPAA2 hardware resources. The MC provides an object-based abstraction for
	31	software drivers to use the DPAA2 hardware.
	32
	33	The MC uses DPAA2 hardware resources such as queues, buffer pools, and
	34	network ports to create functional objects/devices such as network
	35	interfaces, an L2 switch, or accelerator instances.
	36
	37	The MC provides memory-mapped I/O command interfaces (MC portals)
	38	which DPAA2 software drivers use to operate on DPAA2 objects:
	39
	40	+--------------------------------------+
	41	\| OS \|
	42	\| DPAA2 drivers \|
	43	\| \| \|
	44	+-----------------------------\|--------+
	45	\|
	46	\| (create,discover,connect
	47	\| config,use,destroy)
	48	\|
	49	DPAA2 \|
	50	+------------------------\| mc portal \|-+
	51	\| \| \|
	52	\| +- - - - - - - - - - - - -V- - -+ \|
	53	\| \| \| \|
	54	\| \| Management Complex (MC) \| \|
	55	\| \| \| \|
	56	\| +- - - - - - - - - - - - - - - -+ \|
	57	\| \|
	58	\| Hardware Hardware \|
	59	\| Resources Objects \|
	60	\| --------- ------- \|
	61	\| -queues -DPRC \|
	62	\| -buffer pools -DPMCP \|
	63	\| -Eth MACs/ports -DPIO \|
	64	\| -network interface -DPNI \|
65	\| profiles -DPMAC \|
66	\| -queue portals -DPBP \|
67	\| -MC portals ... \|
68	\| ... \|
69	\| \|
70	+--------------------------------------+
71
72	The MC mediates operations such as create, discover,
73	connect, configuration, and destroy. Fast-path operations
74	on data, such as packet transmit/receive, are not mediated by
75	the MC and are done directly using memory mapped regions in
76	DPIO objects.
77
78	Overview of DPAA2 Objects
79	-------------------------
80	The section provides a brief overview of some key objects
81	in the DPAA2 hardware. A simple scenario is described illustrating
82	the objects involved in creating a network interfaces.
83
84	-DPRC (Datapath Resource Container)
85
86	A DPRC is an container object that holds all the other
87	types of DPAA2 objects. In the example diagram below there
88	are 8 objects of 5 types (DPMCP, DPIO, DPBP, DPNI, and DPMAC)
89	in the container.
90
91	+---------------------------------------------------------+
92	\| DPRC \|
93	\| \|
94	\| +-------+ +-------+ +-------+ +-------+ +-------+ \|
95	\| \| DPMCP \| \| DPIO \| \| DPBP \| \| DPNI \| \| DPMAC \| \|
96	\| +-------+ +-------+ +-------+ +---+---+ +---+---+ \|
97	\| \| DPMCP \| \| DPIO \| \|
98	\| +-------+ +-------+ \|
99	\| \| DPMCP \| \|
100	\| +-------+ \|
101	\| \|
102	+---------------------------------------------------------+
103
104	From the point of view of an OS, a DPRC is bus-like. Like
105	a plug-and-play bus, such as PCI, DPRC commands can be used to
106	enumerate the contents of the DPRC, discover the hardware
107	objects present (including mappable regions and interrupts).
108
109	dprc.1 (bus)
110	\|
111	+--+--------+-------+-------+-------+
112	\| \| \| \| \|
113	dpmcp.1 dpio.1 dpbp.1 dpni.1 dpmac.1
114	dpmcp.2 dpio.2
115	dpmcp.3
116
117	Hardware objects can be created and destroyed dynamically, providing
118	the ability to hot plug/unplug objects in and out of the DPRC.
119
120	A DPRC has a mappable mmio region (an MC portal) that can be used
121	to send MC commands. It has an interrupt for status events (like
122	hotplug).
123
124	All objects in a container share the same hardware "isolation context".
125	This means that with respect to an IOMMU the isolation granularity
126	is at the DPRC (container) level, not at the individual object
127	level.
128
129	DPRCs can be defined statically and populated with objects
130	via a config file passed to the MC when firmware starts
131	it. There is also a Linux user space tool called "restool"
132	that can be used to create/destroy containers and objects
133	dynamically.
134
135	-DPAA2 Objects for an Ethernet Network Interface
136
137	A typical Ethernet NIC is monolithic-- the NIC device contains TX/RX
138	queuing mechanisms, configuration mechanisms, buffer management,
139	physical ports, and interrupts. DPAA2 uses a more granular approach
140	utilizing multiple hardware objects. Each object has specialized
141	functions, and are used together by software to provide Ethernet network
142	interface functionality. This approach provides efficient use of finite
143	hardware resources, flexibility, and performance advantages.
144
145	The diagram below shows the objects needed for a simple
146	network interface configuration on a system with 2 CPUs.
147
148	+---+---+ +---+---+
149	CPU0 CPU1
150	+---+---+ +---+---+
151	\| \|
152	+---+---+ +---+---+
153	DPIO DPIO
154	+---+---+ +---+---+
155	\ /
156	\ /
157	\ /
158	+---+---+
159	DPNI --- DPBP,DPMCP
160	+---+---+
161	\|
162	\|
163	+---+---+
164	DPMAC
165	+---+---+
166	\|
167	port/PHY
168
169	Below the objects are described. For each object a brief description
170	is provided along with a summary of the kinds of operations the object
171	supports and a summary of key resources of the object (mmio regions
172	and irqs).
173
174	-DPMAC (Datapath Ethernet MAC): represents an Ethernet MAC, a
175	hardware device that connects to an Ethernet PHY and allows
176	physical transmission and reception of Ethernet frames.
177	-mmio regions: none
178	-irqs: dpni link change
179	-commands: set link up/down, link config, get stats,
180	irq config, enable, reset
181
182	-DPNI (Datapath Network Interface): contains TX/RX queues,
183	network interface configuration, and rx buffer pool configuration
184	mechanisms.
185	-mmio regions: none
186	-irqs: link state
187	-commands: port config, offload config, queue config,
188	parse/classify config, irq config, enable, reset
189
190	-DPIO (Datapath I/O): provides interfaces to enqueue and dequeue
191	packets and do hardware buffer pool management operations. For
192	optimum performance there is typically DPIO per CPU. This allows
193	each CPU to perform simultaneous enqueue/dequeue operations.
194	-mmio regions: queue operations, buffer mgmt
195	-irqs: data availability, congestion notification, buffer
196	pool depletion
197	-commands: irq config, enable, reset
198
199	-DPBP (Datapath Buffer Pool): represents a hardware buffer
200	pool.
201	-mmio regions: none
202	-irqs: none
203	-commands: enable, reset
204
205	-DPMCP (Datapath MC Portal): provides an MC command portal.
206	Used by drivers to send commands to the MC to manage
207	objects.
208	-mmio regions: MC command portal
209	-irqs: command completion
210	-commands: irq config, enable, reset
211
212	Object Connections
213	------------------
214	Some objects have explicit relationships that must
215	be configured:
216
217	-DPNI <--> DPMAC
218	-DPNI <--> DPNI
219	-DPNI <--> L2-switch-port
220	A DPNI must be connected to something such as a DPMAC,
221	another DPNI, or L2 switch port. The DPNI connection
222	is made via a DPRC command.
223
224	+-------+ +-------+
225	\| DPNI \| \| DPMAC \|
226	+---+---+ +---+---+
227	\| \|
228	+==========+
229
230	-DPNI <--> DPBP
231	A network interface requires a 'buffer pool' (DPBP
232	object) which provides a list of pointers to memory
233	where received Ethernet data is to be copied. The
234	Ethernet driver configures the DPBPs associated with
235	the network interface.
236
237	Interrupts
238	----------
239	All interrupts generated by DPAA2 objects are message
240	interrupts. At the hardware level message interrupts
241	generated by devices will normally have 3 components--
242	1) a non-spoofable 'device-id' expressed on the hardware
243	bus, 2) an address, 3) a data value.
244
245	In the case of DPAA2 devices/objects, all objects in the
246	same container/DPRC share the same 'device-id'.
247	For ARM-based SoC this is the same as the stream ID.
248
249
250	DPAA2 Linux Driver Overview
251	---------------------------
252
253	This section provides an overview of the Linux kernel drivers for
254	DPAA2-- 1) the bus driver and associated "DPAA2 infrastructure"
255	drivers and 2) functional object drivers (such as Ethernet).
256
257	As described previously, a DPRC is a container that holds the other
258	types of DPAA2 objects. It is functionally similar to a plug-and-play
259	bus controller.
260
261	Each object in the DPRC is a Linux "device" and is bound to a driver.
262	The diagram below shows the Linux drivers involved in a networking
263	scenario and the objects bound to each driver. A brief description
264	of each driver follows.
265
266	+------------+
267	\| OS Network \|
268	\| Stack \|
269	+------------+ +------------+
270	\| Allocator \|. . . . . . . \| Ethernet \|
271	\|(dpmcp,dpbp)\| \| (dpni) \|
272	+-.----------+ +---+---+----+
273	. . ^ \|
274	. . <data avail, \| \|<enqueue,
275	. . tx confirm> \| \| dequeue>
276	+-------------+ . \| \|
277	\| DPRC driver \| . +---+---V----+ +---------+
278	\| (dprc) \| . . . . . .\| DPIO driver\| \| MAC \|
279	+----------+--+ \| (dpio) \| \| (dpmac) \|
280	\| +------+-----+ +-----+---+
281	\|<dev add/remove> \| \|
282	\| \| \|
283	+----+--------------+ \| +--+---+
284	\| mc-bus driver \| \| \| PHY \|
285	\| \| \| \|driver\|
286	\| /fsl-mc@80c000000 \| \| +--+---+
287	+-------------------+ \| \|
288	\| \|
289	================================ HARDWARE =========\|=================\|======
290	DPIO \|
291	\| \|
292	DPNI---DPBP \|
293	\| \|
294	DPMAC \|
295	\| \|
296	PHY ---------------+
297	===================================================\|========================
298
299	A brief description of each driver is provided below.
300
301	mc-bus driver
302	-------------
303	The mc-bus driver is a platform driver and is probed from an
304	"/fsl-mc@xxxx" node in the device tree passed in by boot firmware.
305	It is responsible for bootstrapping the DPAA2 kernel infrastructure.
306	Key functions include:
307	-registering a new bus type named "fsl-mc" with the kernel,
308	and implementing bus call-backs (e.g. match/uevent/dev_groups)
309	-implemeting APIs for DPAA2 driver registration and for device
310	add/remove
311	-creates an MSI irq domain
312	-do a device add of the 'root' DPRC device, which is needed
313	to bootstrap things
314
315	DPRC driver
316	-----------
317	The dprc-driver is bound DPRC objects and does runtime management
318	of a bus instance. It performs the initial bus scan of the DPRC
319	and handles interrupts for container events such as hot plug.
320
321	Allocator
322	----------
323	Certain objects such as DPMCP and DPBP are generic and fungible,
324	and are intended to be used by other drivers. For example,
325	the DPAA2 Ethernet driver needs:
326	-DPMCPs to send MC commands, to configure network interfaces
327	-DPBPs for network buffer pools
328
329	The allocator driver registers for these allocatable object types
330	and those objects are bound to the allocator when the bus is probed.
331	The allocator maintains a pool of objects that are available for
332	allocation by other DPAA2 drivers.
333
334	DPIO driver
335	-----------
336	The DPIO driver is bound to DPIO objects and provides services that allow
337	other drivers such as the Ethernet driver to receive and transmit data.
338	Key services include:
339	-data availability notifications
340	-hardware queuing operations (enqueue and dequeue of data)
341	-hardware buffer pool management
342
343	There is typically one DPIO object per physical CPU for optimum
344	performance, allowing each CPU to simultaneously enqueue
345	and dequeue data.
346
347	The DPIO driver operates on behalf of all DPAA2 drivers
348	active in the kernel-- Ethernet, crypto, compression,
349	etc.
350
351	Ethernet
352	--------
353	The Ethernet driver is bound to a DPNI and implements the kernel
354	interfaces needed to connect the DPAA2 network interface to
355	the network stack.
356
357	Each DPNI corresponds to a Linux network interface.
358
359	MAC driver
360	----------
361	An Ethernet PHY is an off-chip, board specific component and is managed
362	by the appropriate PHY driver via an mdio bus. The MAC driver
363	plays a role of being a proxy between the PHY driver and the
364	MC. It does this proxy via the MC commands to a DPMAC object.