[PATCH 02/14] staging: fsl-mc: DPAA2 overview readme update

From: Stuart Yoder
Date: Mon Apr 11 2016 - 12:48:55 EST

From: Stuart Yoder <stuart.yoder@xxxxxxx>

incorporated feedback from review comments, other misc cleanup/tweaks

Signed-off-by: Stuart Yoder <stuart.yoder@xxxxxxx>
---
drivers/staging/fsl-mc/README.txt | 138 +++++++++++++++++++++----------------
1 file changed, 80 insertions(+), 58 deletions(-)

diff --git a/drivers/staging/fsl-mc/README.txt b/drivers/staging/fsl-mc/README.txt
index 8214102..179536a 100644
--- a/drivers/staging/fsl-mc/README.txt
+++ b/drivers/staging/fsl-mc/README.txt
@@ -11,11 +11,11 @@ Contents summary
-Overview of DPAA2 objects
-DPAA2 Linux driver architecture overview
-bus driver
- -dprc driver
+ -DPRC driver
-allocator
- -dpio driver
+ -DPIO driver
-Ethernet
- -mac
+ -MAC

DPAA2 Overview
--------------
@@ -37,6 +37,9 @@ 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 |
@@ -77,13 +80,13 @@ 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.
+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 an container object that holds all the other
+ 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.
@@ -101,23 +104,23 @@ the objects involved in creating a network interfaces.
| |
+---------------------------------------------------------+

- 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).
+ 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)
+ DPRC.1 (bus)
|
+--+--------+-------+-------+-------+
| | | | |
- dpmcp.1 dpio.1 dpbp.1 dpni.1 dpmac.1
- dpmcp.2 dpio.2
- dpmcp.3
+ 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
+ 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).

@@ -137,10 +140,11 @@ the objects involved in creating a network interfaces.
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.
+ 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.
@@ -168,46 +172,52 @@ the objects involved in creating a network interfaces.

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).
+ 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
+ -MMIO regions: none
+ -IRQs: DPNI link change
-commands: set link up/down, link config, get stats,
- irq config, enable, reset
+ 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
+ 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
+ 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
+ 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
+ -commands: IRQ config, enable, reset

-DPBP (Datapath Buffer Pool): represents a hardware buffer
pool.
- -mmio regions: none
- -irqs: none
+ -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
+ -MMIO regions: MC command portal
+ -IRQs: command completion
+ -commands: IRQ config, enable, reset

Object Connections
------------------
@@ -268,22 +278,22 @@ of each driver follows.
| Stack |
+------------+ +------------+
| Allocator |. . . . . . . | Ethernet |
- |(dpmcp,dpbp)| | (dpni) |
+ |(DPMCP,DPBP)| | (DPNI) |
+-.----------+ +---+---+----+
. . ^ |
. . <data avail, | |<enqueue,
. . tx confirm> | | dequeue>
+-------------+ . | |
| DPRC driver | . +---+---V----+ +---------+
- | (dprc) | . . . . . .| DPIO driver| | MAC |
- +----------+--+ | (dpio) | | (dpmac) |
+ | (DPRC) | . . . . . .| DPIO driver| | MAC |
+ +----------+--+ | (DPIO) | | (DPMAC) |
| +------+-----+ +-----+---+
|<dev add/remove> | |
| | |
+----+--------------+ | +--+---+
- | mc-bus driver | | | PHY |
+ | MC-bus driver | | | PHY |
| | | |driver|
- | /fsl-mc@80c000000 | | +--+---+
+ | /soc/fsl-mc | | +--+---+
+-------------------+ | |
| |
================================ HARDWARE =========|=================|======
@@ -298,25 +308,27 @@ of each driver follows.

A brief description of each driver is provided below.

- mc-bus driver
+ 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.
+ 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)
- -implemeting APIs for DPAA2 driver registration and for device
+ -implementing 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
+ -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

DPRC driver
-----------
- The dprc-driver is bound DPRC objects and does runtime management
+ 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.
+ and handles interrupts for container events such as hot plug by
+ re-scanning the DPRC.

Allocator
----------
@@ -334,14 +346,20 @@ A brief description of each driver is provided below.
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.
+ 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 each CPU to simultaneously enqueue
+ performance, allowing different CPUs to simultaneously enqueue
and dequeue data.

The DPIO driver operates on behalf of all DPAA2 drivers
@@ -362,3 +380,7 @@ A brief description of each driver is provided below.
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.
--
1.7.9.5