Re: [dpdk-dev] [EXT] Re: [PATCH v3 1/5] net/enetfec: introduce NXP ENETFEC driver

[Apeksha Gupta <apeksha.gupta@nxp.com>]

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Friday, October 1, 2021 8:15 PM
> To: Apeksha Gupta <apeksha.gupta@nxp.com>;
> david.marchand@redhat.com; andrew.rybchenko@oktetlabs.ru
> Cc: dev@dpdk.org; Sachin Saxena <sachin.saxena@nxp.com>; Hemant
> Agrawal <hemant.agrawal@nxp.com>
> Subject: Re: [EXT] Re: [dpdk-dev] [PATCH v3 1/5] net/enetfec: introduce NXP
> ENETFEC driver
> 
> Caution: EXT Email
> 
> On 10/1/2021 11:22 AM, Apeksha Gupta wrote:
> >> -----Original Message-----
> >> From: Ferruh Yigit <ferruh.yigit@intel.com>
> >> Sent: Thursday, September 23, 2021 3:40 PM
> >> To: Apeksha Gupta <apeksha.gupta@nxp.com>;
> >> david.marchand@redhat.com; andrew.rybchenko@oktetlabs.ru;
> >> ferruh.yigit@intel.com
> >> Cc: dev@dpdk.org; Sachin Saxena <sachin.saxena@nxp.com>; Hemant
> >> Agrawal <hemant.agrawal@nxp.com>
> >> Subject: [EXT] Re: [dpdk-dev] [PATCH v3 1/5] net/enetfec: introduce NXP
> >> ENETFEC driver
> >>
> >> Caution: EXT Email
> >>
> >> On 9/9/2021 9:43 PM, Apeksha Gupta wrote:
> >>> ENETFEC (Fast Ethernet Controller) is a network poll mode driver
> >>> for NXP SoC i.MX 8M Mini.
> >>>
> >>
> >> Hi Apeksha,
> >>
> >> Before going into details, I have some high level comments to start with,
> >> please
> >> find comments below.
> >>
> >>> This patch adds skeleton for enetfec driver with probe function.
> >>>
> >>> Signed-off-by: Sachin Saxena <sachin.saxena@nxp.com>
> >>> Signed-off-by: Apeksha Gupta <apeksha.gupta@nxp.com>
> >>
> >> <...>
> >>
> >>> +++ b/doc/guides/nics/enetfec.rst
> >>> @@ -0,0 +1,122 @@
> >>> +.. SPDX-License-Identifier: BSD-3-Clause
> >>> +   Copyright 2021 NXP
> >>> +
> >>> +ENETFEC Poll Mode Driver
> >>> +========================
> >>> +
> >>> +The ENETFEC NIC PMD (**librte_net_enetfec**) provides poll mode
> >> driver
> >>> +support for the inbuilt NIC found in the ** NXP i.MX 8M Mini** SoC.
> >>> +
> >>> +More information can be found at NXP Official Website
> >>>
> >>
> +<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw
> >> ww.nxp.com%2Fproducts%2Fprocessors-and-microcontrollers%2Farm-
> >> processors%2Fi-mx-applications-processors%2Fi-mx-8-processors%2Fi-
> mx-
> >> 8m-mini-arm-cortex-a53-cortex-m4-audio-voice-
> >>
> video%3Ai.MX8MMINI&amp;data=04%7C01%7Capeksha.gupta%40nxp.com
> >> %7C74fdc59c47574d828f7608d97e7a4df3%7C686ea1d3bc2b4c6fa92cd99c5
> c30
> >>
> 1635%7C0%7C1%7C637679886024819097%7CUnknown%7CTWFpbGZsb3d8ey
> >>
> JWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
> >>
> 7C3000&amp;sdata=TjuqIfC8yXwBa3DLCgA7djItfV0UmZ6lA3uLDQ7TFwY%3D
> >> &amp;reserved=0>
> >>> +
> >>> +ENETFEC
> >>> +-------
> >>> +
> >>> +This section provides an overview of the NXP ENETFEC and how it is
> >>> +integrated into the DPDK.
> >>> +
> >>> +Contents summary
> >>> +
> >>> +- ENETFEC overview
> >>> +- ENETFEC features
> >>> +- Supported ENETFEC SoCs
> >>> +- Prerequisites
> >>> +- Driver compilation and testing
> >>> +- Limitations
> >>> +
> >>> +ENETFEC Overview
> >>> +~~~~~~~~~~~~~~~~
> >>> +The i.MX 8M Mini Media Applications Processor is built to achieve both
> >> high
> >>> +performance and low power consumption. ENETFEC is a hardware
> >> programmable
> >>> +packet forwarding engine to provide high performance Ethernet
> interface.
> >>
> >> It has 1Gbps interface, right? It can be good to give more details on the
> >> Ethernet interface.
> > [Apeksha] Okay.
> >>
> >>> +The diagram below shows a system level overview of ENETFEC:
> >>> +
> >>> +
> >>
> ====================================================+=====
> >> ==========
> >>> +   US   +-----------------------------------------+    | Kernel Space
> >>> +     |                                         |    |
> >>> +     |               ENETFEC Driver            |    |
> >>> +     +-----------------------------------------+    |
> >>> +                       ^   |                        |
> >>> +   ENETFEC         RXQ |   | TXQ                    |
> >>> +   PMD                         |   |                        |
> >>> +                       |   v                        |   +----------+
> >>> +                  +-------------+                   |   | fec-uio  |
> >>> +                  | net_enetfec |                   |   +----------+
> >>> +                  +-------------+                   |
> >>> +                       ^   |                        |
> >>> +                   TXQ |   | RXQ                    |
> >>> +                       |   |                        |
> >>> +                       |   v                        |
> >>> +
> >>
> ===================================================+======
> >> =========
> >>> +      +----------------------------------------+
> >>> +      |                                        |       HW
> >>> +      |           i.MX 8M MINI EVK             |
> >>> +      |               +-----+                  |
> >>> +      |               | MAC |                  |
> >>> +      +---------------+-----+------------------+
> >>> +                      | PHY |
> >>> +                      +-----+
> >>> +
> >>> +ENETFEC Ethernet driver is traditional DPDK PMD driver running in the
> >> userspace.
> >>> +The MAC and PHY are the hardware blocks. 'fec-uio' is the UIO driver,
> >> ENETFEC PMD
> >>> +uses UIO interface to interact with kernel for PHY initialisation and for
> >> mapping
> >>> +the allocated memory of register & BD in kernel with DPDK which gives
> >> access to
> >>> +non-cacheable memory for BD.
> >>
> >> Why a specific uio driver, 'fec-uio', is required? I think this is the major
> >> issue to clarify to proceed.
> >>
> >> In DPDK we have full framework to support uio, to do the all memory
> >> mapping,
> >> interrupt configuration etc..., common to all drivers.
> >> But in this case driver is implemented as virtual driver and it handles its
> own
> >> uoi handling itself. Why the driver can't use existing support and
> >> implemented
> >> as physical driver?
> > [Apeksha] Yes you are correct. As per our knowledge, UIO framework is
> there for VM & PCI bus devices and not for vdev bus devices.
> 
> That is part of the comment, why driver implemented as vdev instead of
> physical
> device?
> What is the actual device bus?
[Apeksha] Actual bus is 'platform' bus which is not supported in DPDK.