Re: [PATCH net-next] net: renesas: rswitch: cleanup max_speed setting

On Mon, Feb 03, 2025 at 06:09:41PM +0100, Nikita Yushchenko wrote:

It was observed on spider board that with upstream kernel, PHY
auto-negotiation takes almost 1 second longer than with renesas BSP
kernel. This was tracked down to upstream kernel allowing more PHY modes
than renesas BSP kernel.

To avoid that effect when possible, always set max_speed to not more
than phy_interface allows.

Please could you provide more information about the hardware. Is the
PHY more capable than the MAC?

When you have multi Gigi PHYs, the phy-mode is often taken to be the
starting point. But when the PHY has negotiated a link, it will tell
the MAC what PHY mode it needs to swap to, e.g from SGMII to
2500BaseX, etc.

You should only need max-speed when you have a PHY which can do more
than the MAC.

Also, phylink handles this a lot better than phylib. So you might want
to change rswitch to phylink, especially if you have link speeds > 1G.

	Andrew