linux-kernel - RE: [EXT] Re: [PATCH 0/4] soc: Add support for Marvell OcteonTX2 SDP block

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Date:   Tue, 22 Feb 2022 19:52:13 +0000
From:   Radha Chintakuntla <radhac@...vell.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Satananda Burla <sburla@...vell.com>
Subject: RE: [EXT] Re: [PATCH 0/4] soc: Add support for Marvell OcteonTX2 SDP
 block

> -----Original Message-----
> From: Radha Chintakuntla
> Sent: Thursday, February 10, 2022 2:55 PM
> To: Arnd Bergmann <arnd@...db.de>
> Cc: Linux ARM <linux-arm-kernel@...ts.infradead.org>; Linus Walleij
> <linus.walleij@...aro.org>; Linux Kernel Mailing List <linux-
> kernel@...r.kernel.org>; Satananda Burla <sburla@...vell.com>
> Subject: RE: [EXT] Re: [PATCH 0/4] soc: Add support for Marvell OcteonTX2
> SDP block
> 
> 
> 
> > -----Original Message-----
> > From: Arnd Bergmann <arnd@...db.de>
> > Sent: Thursday, February 10, 2022 8:30 AM
> > To: Radha Chintakuntla <radhac@...vell.com>
> > Cc: Linux ARM <linux-arm-kernel@...ts.infradead.org>; Arnd Bergmann
> > <arnd@...db.de>; Linus Walleij <linus.walleij@...aro.org>; Linux
> > Kernel Mailing List <linux-kernel@...r.kernel.org>; Satananda Burla
> > <sburla@...vell.com>
> > Subject: [EXT] Re: [PATCH 0/4] soc: Add support for Marvell OcteonTX2
> > SDP block
> >
> > External Email
> >
> > ----------------------------------------------------------------------
> > On Wed, Feb 9, 2022 at 11:42 PM Radha Mohan Chintakuntla
> > <radhac@...vell.com> wrote:
> > >
> > > The Marvell OcteonTX2's SDP block is a interface for sending and
> > > receiving ethernet packets over the PCIe interface when OcteonTX2 is
> > > in PCIe endpoint mode. It interfaces with the OcteonTX2's NIX block
> > queues.
> >
> > Hi Radha,
> >
> > I'm not sure drivers/soc/ is the right place for it. I have not done
> > an actual review so far, but I have some high-level questions to clarify how
> this fits in:
> >
> > When you say it is meant for passing ethernet packets, why is it not
> > an ethernet driver?
> 
> The SDP block sits in between the PCI Endpoint controller and the Network
> block (NIX). It does an implicit DMA from a remote host to Octeon and has
> queues to direct to the NIX queues. The host side will have a netdev driver
> which sends/receives packets on the SDP queues so they make it to the NIX.
> SDP driver doesn't do any packet transmit or receive by itself so that's why it
> is not a netdev driver.
> 
> >
> > If this drives the PCIe endpoint mode, how does it interface with the
> > pci endpoint framework? It looks like a normal PCI driver.
> The block does not drive the endpoint mode as such. The driver is just
> settings up the connection between SDP and NIX. It doesn't touch any of the
> endpoint registers or setup the endpoint connection. Most of that is done by
> firmware which detects the mode and sets up the EP controller.
> >
> > What hardware does this run on? Is this only usable when both the host
> > side and the endpoint side are Octexon TX2 machines with their packet
> > engines, or can one of the two be a different machine that has PCIe
> > host or endpoint device support?
> It runs on Marvell OcteonTX2 when is in PCIe Endpoint. But the host can be
> anything - we have tested on x86 and arm64 hosts so far.
> The host side will have a netdev driver that will go into the drivers/net area.
> >
Hi Arnd,
Any more information you need on this ?

Regards,
Radha