Re: [PATCH] net: phy: microchip_t1: LAN887X: Fix device init issues.

[Josef Raschen <josef@raschen.org>]

Hello Andrew,

Thanks for your feedback.

On 9/26/25 00:00, Andrew Lunn wrote:
> On Thu, Sep 25, 2025 at 10:52:22PM +0200, Josef Raschen wrote:
>> Currently, for a LAN8870 phy, before link up, a call to ethtool to set
>> master-slave fails with 'operation not supported'. Reason: speed, duplex
>> and master/slave are not properly initialized.
>>
>> This change sets proper initial states for speed and duplex and publishes
>> master-slave states. A default link up for speed 1000, full duplex and
>> slave mode then works without having to call ethtool.
> 
> Hi Josef
> 
> What you are missing from the commit message is an explanation why the
> LAN8870 is special, it needs to do something no other PHY does. Is
> there something broken with this PHY? Some register not following
> 802.3?
> 
>      Andrew
> 
> ---
> pw-bot: cr
> 

Special about the LAN8870 might be that it is a dual speed T1 phy.
As most other T1 pyhs have only one possible configuration the unknown
speed configuration was not a problem so far. But here, when
calling link up without manually setting the speed before, it seems to
pick speed 100 in phy_sanitize_settings(). I assume that this is not the
desired behavior?

The second problem is that ethtool initially does not allow to set
master-slave at all. You first have to call ethtool without the
master-slave argument, then again with it. This is fixed by reading
the master slave configuration from the device which seems to be missing
in the .config_init and .config_aneg functions. I took this solution 
from net/phy/dp83tg720.c.

Regards,
Josef