On Thu, Nov 30, 2017 at 06:15:20PM +0000, Russell King - ARM Linux wrote:
> On Thu, Nov 30, 2017 at 06:41:27PM +0100, Andrew Lunn wrote:
> > SGMII supports passing auto-negotiation results from the PHY to the
> > MAC. 1000BASE-X does not.
> >
> > SGMII supports the PHY running at 10, 100, and 1000 Mbps. But to
> > support this, the MAC needs to replicate the bits 100, or 10 times
> > when the PHY is running in 10 or 100Mbps mode.
> >
> > So with your 2.5G SGMII, you need to replicate the bits 250, 25, or
> > 2.5 times if they PHY is running at lower speeds. This last one is
> > interesting.
>
> That's not what I've read so far - but I don't know about the PHY
> in this exact case because the docs are only available under NDA
> (which makes it incredibly difficult to have this discussion.)
>
> However, from what I can ascertain from a Xilinx document, 2.5G is
> 1G SGMII clocked 2.5x faster. When in 2.5G mode, the other modes
> are unavailable.
Hi Russell
Thanks for looking into the details.
So you need the PHY driver to see what it has negotiated, and when it
calls the adjust_link callback, the MAC needs look at the
phydev->interface and set the MAC to 2.5G SGMII or SGMII.
Same as the Marvell 10G PHY driver flips between
PHY_INTERFACE_MODE_10GKR and PHY_INTERFACE_MODE_SGMII depending on
what it has negotiated.
Andrew
