linux-kernel - Re: [PATCH net-next v3 2/2] net: ethernet: Add driver for Sunplus SP7021

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Message-ID: <YakYlHzvlAI+1at+@lunn.ch>
Date:   Thu, 2 Dec 2021 20:03:48 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Wells Lu 呂芳騰 <wells.lu@...plus.com>
Cc:     Wells Lu <wellslutw@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Vincent Shih 施錕鴻 
        <vincent.shih@...plus.com>
Subject: Re: [PATCH net-next v3 2/2] net: ethernet: Add driver for Sunplus
 SP7021

On Thu, Dec 02, 2021 at 06:46:40PM +0000, Wells Lu 呂芳騰 wrote:
> Hi Andrew,
> 
> Thank you for explanation.
> 
> I'll add phy_support_asym_pause() after PHY connected next patch.
> 
> I found some drivers call phy_set_max_speed() to set PHY speed to
> 100M after PHY connected. Is that necessary?

> From 'supported', PHY supports 10M/100M already.

You need phy_set_max_speed() when it is possible to connect a 10/100
MAC to a 1G PHY.  You sometime do this because a 1G PHY is cheaper
than a 100M PHY. Unless limited, the PHY will advertise and could
negotiate a 1G link, but the MAC could then not support it. If it is
not physically possible to connect a 1G PHY to your MAC, you don't
need to worry.

> I also found some drivers call phy_start_aneg() after PHY started.

It is not needed.

   Andrew