netdev - RE: [for-next 4/6] net/mlx5: FPGA, Add basic support for Innova

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Date:   Mon, 29 May 2017 15:58:33 +0000
From:   Ilan Tayari <ilant@...lanox.com>
To:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>
CC:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Saeed Mahameed <saeedm@....mellanox.co.il>,
        "David S. Miller" <davem@...emloft.net>,
        "Doug Ledford" <dledford@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "jsorensen@...com" <jsorensen@...com>,
        "Andy Shevchenko" <andy.shevchenko@...il.com>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        Alan Tull <atull@...nsource.altera.com>,
        "yi1.li@...ux.intel.com" <yi1.li@...ux.intel.com>,
        Boris Pismenny <borisp@...lanox.com>
Subject: RE: [for-next 4/6] net/mlx5: FPGA, Add basic support for Innova

> -----Original Message-----
> From: Jason Gunthorpe [mailto:jgunthorpe@...idianresearch.com]
> Subject: Re: [for-next 4/6] net/mlx5: FPGA, Add basic support for Innova
> 
> On Sun, May 28, 2017 at 07:22:27AM +0000, Ilan Tayari wrote:
> 
> > This is neither PCI-bar mapped, nor mailbox command.
> > The FPGA is indeed a bump-on-the-wire.
> > (It has I2C to the CX4 chip, but that is for debug purposes, and too
> slow
> > to perform real programming)
> 
> Wait.. So if it truely has nothing to do with the existing mellanox
> driver, then nothing more than the fpga loader should be in the mlx5
> directory?

True, except in specific cases when the FPGA may mangle the packets in
a way that the netdevice configures, and the driver needs to adapt the
data path.

Such is the case of IPSec and TLS offloads.
Those are tied to the mlx5 Ethernet driver (isolated with a kconfig).

> 
> > One flavor of the product, the Innova Flex, allows customer logic in the
> > FPGA. But even then it is "wrapped" by Mellanox shell logic.
> > We plan to have an in-kernel API for writing client drivers for Innova
> > Flex.
> 
> The FPGA subsystem already has APIs for partial reconfiguration use
> cases, you probably should not re-invent that under the mlx5 driver.

When the time comes to introduce the API for that, we will investigate all
Options available. Currently this is not in the plans for Linux.

(We do have an out-of-tree 'hack' driver for this, but it's planned to be
replaced with something more appropriate later on)

> 
> Jason