RE: [PATCH net-next v2 2/2] net: phy: microchip_t1: Auto-negotiation support for LAN887x

[Tarun.Alle]

Hi Andrew,

Thanks for the review.

> -----Original Message-----
> From: Andrew Lunn <andrew@xxxxxxx>
> Sent: Tuesday, December 17, 2024 5:10 AM
> To: Tarun Alle - I68638 <Tarun.Alle@xxxxxxxxxxxxx>
> Cc: Arun Ramadoss - I17769 <Arun.Ramadoss@xxxxxxxxxxxxx>;
> UNGLinuxDriver <UNGLinuxDriver@xxxxxxxxxxxxx>; hkallweit1@xxxxxxxxx;
> linux@xxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx;
> kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net-next v2 2/2] net: phy: microchip_t1: Auto-negotiation
> support for LAN887x
> 
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> On Mon, Dec 16, 2024 at 09:28:30PM +0530, Tarun Alle wrote:
> > Adds auto-negotiation support for lan887x T1 phy. After this commit,
> > by default auto-negotiation is on and default advertised speed is 1000M.
> 
> So i asked about the implications of this. I would of expected something like:
> 
> This will break any system which expects forced behaviour, without actually
> configuring forced behaviour both on the local system and where the link
> partner is expecting forced configuration, not autoneg.
> 

We confirmed that there are no customers who are directly using the net-next. 
Hence, we are setting this to default auto-neg which is also chip default. But if
any regressions on T1PHYs are dependent,  we will address this default setting.

> I think we also need some more details about the autoneg in the commit
> message. When used against a standards conforming 100M PHY, negotiation
> will fail by default, because this PHY is not conformant with 100M, or 1G
> autoneg.
> 

I should have given the same errata details in the commit message. Will take care.

> I don't like you are going to cause regressions, especially when you have decided
> regressions are worth it for a half broken autoneg.
> 
> I actually think it should default to fixed, as it is today. Maybe with the option to
> enable the broken autoneg. This is different to all PHYs we have today, but we try
> hard to avoid regressions.
> 
> What are the plans for this PHY? Will there be a new revision soon which fixes
> the broken autoneg? Maybe you should forget about autoneg for this revision
> of this PHY, it is too broken, and wait for the next revision which actually
> conforms to the standard?
> 

I understand your point and I agree with you. We can drop this patch for this chip 
revision as we have plans for new revision.

>         Andrew

Thanks,
Tarun Alle.