netdev - Re: [PATCH net-next v2 1/1] net: phy: dp83867: retrigger SGMII AN when link change

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Date:   Thu, 26 May 2022 14:32:14 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Tan Tee Min <tee.min.tan@...ux.intel.com>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Dan Murphy <dmurphy@...com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Voon Wei Feng <weifeng.voon@...el.com>,
        Sit Michael Wei Hong <michael.wei.hong.sit@...el.com>,
        Ling Pei Lee <pei.lee.ling@...el.com>,
        Looi Hong Aun <hong.aun.looi@...el.com>,
        Wong Vee Khee <vee.khee.wong@...el.com>,
        Tan Tee Min <tee.min.tan@...el.com>
Subject: Re: [PATCH net-next v2 1/1] net: phy: dp83867: retrigger SGMII AN
 when link change

On Thu, May 26, 2022 at 05:03:47PM +0800, Tan Tee Min wrote:
> There is a limitation in TI DP83867 PHY device where SGMII AN is only
> triggered once after the device is booted up. Even after the PHY TPI is
> down and up again, SGMII AN is not triggered and hence no new in-band
> message from PHY to MAC side SGMII.
> 
> This could cause an issue during power up, when PHY is up prior to MAC.
> At this condition, once MAC side SGMII is up, MAC side SGMII wouldn`t
> receive new in-band message from TI PHY with correct link status, speed
> and duplex info.
> 
> As suggested by TI, implemented a SW solution here to retrigger SGMII
> Auto-Neg whenever there is a link change.

Is there a bit in the PHY which reports host side link? There is no
point triggering an AN if there is already link.

      Andrew