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From:   Razvan Stefanescu <razvan.stefanescu@nxp.com>
To:     Andrew Lunn <andrew@lunn.ch>
CC:     Arnd Bergmann <arnd@arndb.de>, gregkh <gregkh@linuxfoundation.org>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Stuart Yoder <stuyoder@gmail.com>,
        Ruxandra Ioana Ciocoi Radulescu <ruxandra.radulescu@nxp.com>,
        Roy Pledge <roy.pledge@nxp.com>,
        Networking <netdev@vger.kernel.org>,
        Ioana Ciornei <ioana.ciornei@nxp.com>
Subject: RE: [PATCH v3 2/4] bus: fsl-mc: add restool userspace support
Thread-Topic: [PATCH v3 2/4] bus: fsl-mc: add restool userspace support
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Date:   Tue, 3 Apr 2018 11:12:52 +0000
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Hello Andrew,

> -----Original Message-----
> From: Andrew Lunn [mailto:andrew@lunn.ch]
> Sent: Monday, April 2, 2018 4:45 PM
> To: Ioana Ciornei <ioana.ciornei@nxp.com>
> Cc: Arnd Bergmann <arnd@arndb.de>; gregkh
> <gregkh@linuxfoundation.org>; Laurentiu Tudor
> <laurentiu.tudor@nxp.com>; Linux Kernel Mailing List <linux-
> kernel@vger.kernel.org>; Stuart Yoder <stuyoder@gmail.com>; Ruxandra
> Ioana Ciocoi Radulescu <ruxandra.radulescu@nxp.com>; Razvan Stefanescu
> <razvan.stefanescu@nxp.com>; Roy Pledge <roy.pledge@nxp.com>;
> Networking <netdev@vger.kernel.org>
> Subject: Re: [PATCH v3 2/4] bus: fsl-mc: add restool userspace support
>=20
> Hi Ioana
>=20
> > The commands listed above are for creating/destroying DPAA2 objects
> > in Management Complex and not for runtime configuration where
> > standard userspace tools are used.
>=20
> Please can you explain why this is not just plumbing inside a
> switchdev driver?
>=20
> The hardware has a number of physical ports. So on probe, i would
> expect it to create a DPMAC, DPNI, and DPIO for each port, and a linux
> netdev. From then on, standard tools are all that are needed. The
> switchdev driver can create a l2 switch object when the user uses the
> ip link add name br0 type bridge. It can then connect the switch
> object to the DPNI when the user adds an interface to the switch, etc.
>=20

I'll chime in as you mentioned switchdev driver.=20

DPAA2 offers several object-based abstractions for modeling network
related devices (interfaces, L2 Ethernet switch) or accelerators
(DPSECI - crypto and DPDCEI - compression), the latter not up-streamed yet.
They are modeled using various low-level resources (e.g. queues,
classification tables, physical ports) and have multiple configuration and
interconnectivity options, managed by the Management Complex.=20
Resources are limited and they are only used when needed by the objects,
to accommodate more configurations and usage scenarios.
=20
Some of the objects have a 1-to-1 correspondence to physical resources
(e.g. DPMACs to physical ports), while others (like DPNIs and DPSW)
can be seen as a collection of the mentioned resources. The types and=20
number of such objects are not predetermined.

When the board boots up, none of them exist yet. Restool allows a user to
define the system topology, by providing a way to dynamically create, destr=
oy
and interconnect these objects.

After an object is created, it will be presented on the fsl-mc bus. A drive=
r
is loaded to implement the required kernel interfaces specific to that obje=
ct
type. Kernel can boot and afterwards the DPAA2 objects are added, as the us=
er
requires.

As you mentioned DPMACs: objects of this type can be connected only to a DP=
NI
(a network interface like object) or to a DPSW (L2 ethernet switch) port.
Likewise, a DPNI can have only one connection (to a DPMAC, a DPSW port or
another DPNI object).

Here's several examples of valid connection types:
  * DPMAC <----> DPNI (standard network i/f corresponding to a physical por=
t)
  * DPMAC <----> DPSW (physical port in a switch)
  * DPNI <----> DPSW (virtual network interface connected to a switch port)
  * DPNI <----> DPNI

In the latter case, the two DPNIs will not be connected to any physical
port, but can be used as a point-to-point connection between two virtual
machines for instance.

So, it is not possible to connect a DPNI to a DPSW after it was connected
to a DPMAC. The DPNI-DPMAC pair would have to be disconnected and
DPMAC will be reconnected to the switch. DPNI interface that is no longer
connected to a DPMAC will be destroyed and any new addition/deletion of
a DPNI/DPMAC interface to the switch port will trigger the entire switch
re-configuration.

Best regards,
Razvan Stefanescu