[PATCH net-next V2 2/2] net: axienet: Add support for 2500base-X only configuration.

[Gupta, Suraj]

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Andrew Lunn <andrew at lunn.ch>
> Sent: Wednesday, March 12, 2025 9:03 PM
> To: Gupta, Suraj <Suraj.Gupta2 at amd.com>
> Cc: Russell King <linux at armlinux.org.uk>; Pandey, Radhey Shyam
> <radhey.shyam.pandey at amd.com>; andrew+netdev at lunn.ch;
> davem at davemloft.net; edumazet at google.com; kuba at kernel.org;
> pabeni at redhat.com; robh at kernel.org; krzk+dt at kernel.org; conor+dt at kernel.org;
> Simek, Michal <michal.simek at amd.com>; netdev at vger.kernel.org;
> devicetree at vger.kernel.org; linux-kernel at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org; git (AMD-Xilinx) <git at amd.com>; Katakam, Harini
> <harini.katakam at amd.com>
> Subject: Re: [PATCH net-next V2 2/2] net: axienet: Add support for 2500base-X only
> configuration.
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> On Wed, Mar 12, 2025 at 03:06:32PM +0000, Gupta, Suraj wrote:
> > [AMD Official Use Only - AMD Internal Distribution Only]
> >
> > > -----Original Message-----
> > > From: Andrew Lunn <andrew at lunn.ch>
> > > Sent: Wednesday, March 12, 2025 8:29 PM
> > > To: Gupta, Suraj <Suraj.Gupta2 at amd.com>
> > > Cc: Russell King <linux at armlinux.org.uk>; Pandey, Radhey Shyam
> > > <radhey.shyam.pandey at amd.com>; andrew+netdev at lunn.ch;
> > > davem at davemloft.net; edumazet at google.com; kuba at kernel.org;
> > > pabeni at redhat.com; robh at kernel.org; krzk+dt at kernel.org;
> > > conor+dt at kernel.org; Simek, Michal <michal.simek at amd.com>;
> > > netdev at vger.kernel.org; devicetree at vger.kernel.org;
> > > linux-kernel at vger.kernel.org; linux-arm- kernel at lists.infradead.org;
> > > git (AMD-Xilinx) <git at amd.com>; Katakam, Harini
> > > <harini.katakam at amd.com>
> > > Subject: Re: [PATCH net-next V2 2/2] net: axienet: Add support for
> > > 2500base-X only configuration.
> > >
> > > Caution: This message originated from an External Source. Use proper
> > > caution when opening attachments, clicking links, or responding.
> > >
> > >
> > > > > On Wed, Mar 12, 2025 at 02:25:27PM +0100, Andrew Lunn wrote:
> > > > > > > +   /* AXI 1G/2.5G ethernet IP has following synthesis options:
> > > > > > > +    * 1) SGMII/1000base-X only.
> > > > > > > +    * 2) 2500base-X only.
> > > > > > > +    * 3) Dynamically switching between (1) and (2), and is not
> > > > > > > +    * implemented in driver.
> > > > > > > +    */
> > >
> > > > - Keeping previous discussion short, identification of (3) depends
> > > > on how user implements switching logic in FPGA (external GT or RTL
> > > > logic). AXI 1G/2.5G IP provides only static speed selections and
> > > > there is no standard register to communicate that to software.
> > >
> > > So if anybody has synthesised it as 3) this change will break their system?
> > >
> > >         Andrew
> >
> > It will just restrict their system to (2)
>
> Where as before, it was doing SGMII/1000base-X only. So such systems break?
>
>         Andrew

If the user wants (3), they need to add their custom FPGA logic which anyway will require additional driver changes. (3) was not completely supported by existing driver.