diff mbox series

[v18,5/8] doc: add DMA device library guide

Message ID 1630580057-29295-6-git-send-email-fengchengwen@huawei.com (mailing list archive)
State Superseded, archived
Headers show
Series support dmadev | expand

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Context Check Description
ci/checkpatch success coding style OK

Commit Message

Fengchengwen Sept. 2, 2021, 10:54 a.m. UTC
This patch adds dmadev library guide.

Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Acked-by: Conor Walsh <conor.walsh@intel.com>
---
 doc/guides/prog_guide/dmadev.rst     | 125 ++++++++++++++++
 doc/guides/prog_guide/img/dmadev.svg | 283 +++++++++++++++++++++++++++++++++++
 doc/guides/prog_guide/index.rst      |   1 +
 3 files changed, 409 insertions(+)
 create mode 100644 doc/guides/prog_guide/dmadev.rst
 create mode 100644 doc/guides/prog_guide/img/dmadev.svg
diff mbox series

Patch

diff --git a/doc/guides/prog_guide/dmadev.rst b/doc/guides/prog_guide/dmadev.rst
new file mode 100644
index 0000000..e47a164
--- /dev/null
+++ b/doc/guides/prog_guide/dmadev.rst
@@ -0,0 +1,125 @@ 
+.. SPDX-License-Identifier: BSD-3-Clause
+   Copyright 2021 HiSilicon Limited
+
+DMA Device Library
+====================
+
+The DMA library provides a DMA device framework for management and provisioning
+of hardware and software DMA poll mode drivers, defining generic APIs which
+support a number of different DMA operations.
+
+
+Design Principles
+-----------------
+
+The DMA library follows the same basic principles as those used in DPDK's
+Ethernet Device framework and the RegEx framework. The DMA framework provides
+a generic DMA device framework which supports both physical (hardware)
+and virtual (software) DMA devices as well as a generic DMA API which allows
+DMA devices to be managed and configured and supports DMA operations to be
+provisioned on DMA poll mode driver.
+
+.. _figure_dmadev:
+
+.. figure:: img/dmadev.*
+
+The above figure shows the model on which the DMA framework is built on:
+
+ * The DMA controller could have multiple hardware DMA channels (aka. hardware
+   DMA queues), each hardware DMA channel should be represented by a dmadev.
+ * The dmadev could create multiple virtual DMA channels, each virtual DMA
+   channel represents a different transfer context. The DMA operation request
+   must be submitted to the virtual DMA channel. e.g. Application could create
+   virtual DMA channel 0 for memory-to-memory transfer scenario, and create
+   virtual DMA channel 1 for memory-to-device transfer scenario.
+
+
+Device Management
+-----------------
+
+Device Creation
+~~~~~~~~~~~~~~~
+
+Physical DMA controllers are discovered during the PCI probe/enumeration of the
+EAL function which is executed at DPDK initialization, this is based on their
+PCI BDF (bus/bridge, device, function). Specific physical DMA controllers, like
+other physical devices in DPDK can be listed using the EAL command line options.
+
+The dmadevs are dynamically allocated by using the API
+``rte_dmadev_pmd_allocate`` based on the number of hardware DMA channels.
+
+
+Device Identification
+~~~~~~~~~~~~~~~~~~~~~
+
+Each DMA device, whether physical or virtual is uniquely designated by two
+identifiers:
+
+- A unique device index used to designate the DMA device in all functions
+  exported by the DMA API.
+
+- A device name used to designate the DMA device in console messages, for
+  administration or debugging purposes.
+
+
+Device Configuration
+~~~~~~~~~~~~~~~~~~~~
+
+The rte_dmadev_configure API is used to configure a DMA device.
+
+.. code-block:: c
+
+   int rte_dmadev_configure(uint16_t dev_id,
+                            const struct rte_dmadev_conf *dev_conf);
+
+The ``rte_dmadev_conf`` structure is used to pass the configuration parameters
+for the DMA device for example the number of virtual DMA channels to set up,
+indication of whether to enable silent mode.
+
+
+Configuration of Virtual DMA Channels
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The rte_dmadev_vchan_setup API is used to configure a virtual DMA channel.
+
+.. code-block:: c
+
+   int rte_dmadev_vchan_setup(uint16_t dev_id, uint16_t vchan,
+                              const struct rte_dmadev_vchan_conf *conf);
+
+The ``rte_dmadev_vchan_conf`` structure is used to pass the configuration
+parameters for the virtual DMA channel for example transfer direction, number of
+descriptor for the virtual DMA channel, source device access port parameter,
+destination device access port parameter.
+
+
+Device Features and Capabilities
+--------------------------------
+
+DMA devices may support different feature sets. The ``rte_dmadev_info_get`` API
+can be used to get the device info and supported features.
+
+Silent mode is a special device capability which does not require the
+application to invoke dequeue APIs.
+
+
+Enqueue / Dequeue APIs
+~~~~~~~~~~~~~~~~~~~~~~
+
+Enqueue APIs such as ``rte_dmadev_copy`` and ``rte_dmadev_fill`` can be used to
+enqueue operations to hardware. If an enqueue is successful, a ``ring_idx`` is
+returned. This ``ring_idx`` can be used by applications to track per operation
+metadata in an application-defined circular ring.
+
+The ``rte_dmadev_submit`` API is used to issue doorbell to hardware.
+Alternatively the ``RTE_DMA_OP_FLAG_SUBMIT`` flag can be passed to the enqueue
+APIs to also issue the doorbell to hardware.
+
+There are two dequeue APIs ``rte_dmadev_completed`` and
+``rte_dmadev_completed_status``, these are used to obtain the results of
+the enqueue requests. ``rte_dmadev_completed`` will return the number of
+successfully completed operations. ``rte_dmadev_completed_status`` will return
+the number of completed operations along with the status of each operation
+(filled into the ``status`` array passed by user). These two APIs can also
+return the last completed operation's ``ring_idx`` which could help user track
+operations within their own application-defined rings.
diff --git a/doc/guides/prog_guide/img/dmadev.svg b/doc/guides/prog_guide/img/dmadev.svg
new file mode 100644
index 0000000..157d7eb
--- /dev/null
+++ b/doc/guides/prog_guide/img/dmadev.svg
@@ -0,0 +1,283 @@ 
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diff --git a/doc/guides/prog_guide/index.rst b/doc/guides/prog_guide/index.rst
index 2dce507..0abea06 100644
--- a/doc/guides/prog_guide/index.rst
+++ b/doc/guides/prog_guide/index.rst
@@ -29,6 +29,7 @@  Programmer's Guide
     regexdev
     rte_security
     rawdev
+    dmadev
     link_bonding_poll_mode_drv_lib
     timer_lib
     hash_lib