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

From: Tan Tee Min <tee.min.tan@linux.intel.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Heiner Kallweit <hkallweit1@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Dan Murphy <dmurphy@ti.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, Voon Wei Feng <weifeng.voon@intel.com>,
	Sit Michael Wei Hong <michael.wei.hong.sit@intel.com>,
	Ling Pei Lee <pei.lee.ling@intel.com>,
	Looi Hong Aun <hong.aun.looi@intel.com>,
	Wong Vee Khee <vee.khee.wong@intel.com>,
	Tan Tee Min <tee.min.tan@intel.com>
Subject: Re: [PATCH net-next v2 1/1] net: phy: dp83867: retrigger SGMII AN when link change
Date: Fri, 27 May 2022 09:47:09 +0800	[thread overview]
Message-ID: <20220527014709.GA26992@linux.intel.com> (raw)
In-Reply-To: <Yo9zTmMduwel8XeZ@lunn.ch>

On Thu, May 26, 2022 at 02:32:14PM +0200, Andrew Lunn wrote:
> On Thu, May 26, 2022 at 05:03:47PM +0800, Tan Tee Min wrote:
> > 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

Thanks for your comment.

There is no register bit in TI PHY which reports the SGMII AN link status.
But, there is a bit that only reports the SGMII AN completion status.

In this case, the PHY side SGMII AN has been already completed prior to MAC is up.
So, once MAC side SGMII is up, MAC side SGMII wouldn`t receive any new
in-band message from TI PHY.

Thanks,
Tee Min