[PATCH net-next 2/2] net: axienet: Add support for AXI 2.5G MAC

[Gupta, Suraj]

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Russell King <linux at armlinux.org.uk>
> Sent: Thursday, February 20, 2025 5:14 PM
> To: Gupta, Suraj <Suraj.Gupta2 at amd.com>
> Cc: Sean Anderson <sean.anderson at linux.dev>; Andrew Lunn <andrew at lunn.ch>;
> andrew+netdev at lunn.ch; davem at davemloft.net; edumazet at google.com;
> kuba at kernel.org; pabeni at redhat.com; Simek, Michal <michal.simek at amd.com>;
> Pandey, Radhey Shyam <radhey.shyam.pandey at amd.com>; horms at kernel.org;
> netdev at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; git (AMD-Xilinx) <git at amd.com>; Katakam, Harini
> <harini.katakam at amd.com>
> Subject: Re: [PATCH net-next 2/2] net: axienet: Add support for AXI 2.5G MAC
>
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>
> On Thu, Feb 20, 2025 at 11:30:52AM +0000, Gupta, Suraj wrote:
> > Sorry for picking up this thread after long time, we checked
> > internally with AMD IP and hardware experts and it is true that you
> > can use this MAC and PCS to operate at 1G and 2.5G both. It is also
> > possible to switch between these two speeds dynamically using external
> > GT and/or if an external RTL logic is implemented in the FPGA. That
> > will include some GPIO or register based selections to change the
> > clock and configurations to switch between the speeds.
> > Our current solution does not support this and is meant for a static
> > speed selection only.
>
> Thanks for getting back on this.
>
> Okay, so it's a synthesis option, where that may be one of:
>
> 1. SGMII/1000base-X only
> 2. 2500base-X only
> 3. dynamically switching between (1) and (2).
>
> > We'll use MAC ability register to detect if MAC is configured for
> > 2.5G. Will it be fine to advertise both 1G and 2.5G in that case?
>
> Please document in a comment that the above are synthesis options, and that
> dynamically changing between them is possible but not implemented by the driver.
> Note that should anyone use axienet for SFP modules, then (1) is essentially the
> base functionality, (2) is very limiting, and (3) would be best.
>
> Not only will one want to limit the MAC capabilities, but also the supported interface
> modes. As it's been so long since the patch was posted, I don't remember whether it
> did that or not.
>

Sure, will document in the comment and limit both mac capabilities and supported interfaces accordingly.
Thank you for your quick response and guidance. I really appreciate your support!

> Thanks.
>
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