Re: [PATCH 1/1] net: phy: marvell: avoid bringing down fibre link when autoneg is bypassed

[Andrew Lunn]

On Thu, Oct 03, 2024 at 12:25:12PM +1000, Qingtao Cao wrote:
> On 88E151x the SGMII autoneg bypass mode defaults to be enabled. When it is
> activated, the device assumes a link-up status with existing configuration
> in BMCR, avoid bringing down the fibre link in this case
> 
> Test case:
> 1. Two 88E151x connected with SFP, both enable autoneg, link is up with speed
>    1000M
> 2. Disable autoneg on one device and explicitly set its speed to 1000M
> 3. The fibre link can still up with this change, otherwise not.

What is actually wrong here?

If both ends are performing auto-neg, i would expect a link at the
highest speeds both link peers support.

If one peer is doing autoneg, the other not, i expect link down, this
is not a valid configuration, since one peer is going to fail to
auto-neg.

If both peers are using forced 1000M, i would expect a link.

   Andrew