Re: [dpdk-dev] [PATCH v20 5/7] doc: add DMA device library guide

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sat, Sep 4, 2021 at 3:44 PM Chengwen Feng <fengchengwen@huawei.com> wrote:
>
> This patch adds dmadev library guide.
>
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> Acked-by: Conor Walsh <conor.walsh@intel.com>
> Reviewed-by: Kevin Laatz <kevin.laatz@intel.com>

Acked-by: Jerin Jacob <jerinj@marvell.com>


> ---
>  MAINTAINERS                          |   1 +
>  doc/guides/prog_guide/dmadev.rst     | 125 ++++++++++++
>  doc/guides/prog_guide/img/dmadev.svg | 283 +++++++++++++++++++++++++++
>  doc/guides/prog_guide/index.rst      |   1 +
>  4 files changed, 410 insertions(+)
>  create mode 100644 doc/guides/prog_guide/dmadev.rst
>  create mode 100644 doc/guides/prog_guide/img/dmadev.svg
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9885cc56b7..e237e9406b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -499,6 +499,7 @@ F: doc/guides/prog_guide/rawdev.rst
>  DMA device API - EXPERIMENTAL
>  M: Chengwen Feng <fengchengwen@huawei.com>
>  F: lib/dmadev/
> +F: doc/guides/prog_guide/dmadev.rst
>
>
>  Memory Pool Drivers
> diff --git a/doc/guides/prog_guide/dmadev.rst b/doc/guides/prog_guide/dmadev.rst
> new file mode 100644
> index 0000000000..e47a164850
> --- /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 0000000000..157d7eb7dc
> --- /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 2dce507f46..0abea06b24 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
> --
> 2.33.0
>