netdev - Re: [PATCH] net: phy: marvell: avoid pause mode on SGMII-to-Copper for 88e151x

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Message-Id: <20171218.150456.625421280463615366.davem@davemloft.net>
Date:   Mon, 18 Dec 2017 15:04:56 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     rmk+kernel@...linux.org.uk
Cc:     andrew@...n.ch, f.fainelli@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: phy: marvell: avoid pause mode on SGMII-to-Copper
 for 88e151x

From: Russell King <rmk+kernel@...linux.org.uk>
Date: Fri, 15 Dec 2017 16:10:20 +0000

> Observed on the 88e1512 in SGMII-to-Copper mode, negotiating pause
> is unreliable.  While the pause bits can be set in the advertisment
> register, they clear shortly after negotiation with a link partner
> commences irrespective of the cause of the negotiation.
> 
> While these bits may be correctly conveyed to the link partner on the
> first negotiation, a subsequent negotiation (eg, due to negotiation
> restart by the link partner, or reconnection of the cable) will result
> in the link partner seeing these bits as zero, while the kernel
> believes that it has advertised pause modes.
> 
> This leads to the local kernel evaluating (eg) symmetric pause mode,
> while the remote end evaluates that we have no pause mode capability.
> 
> Since we can't guarantee the advertisment, disable pause mode support
> with this PHY when used in SGMII-to-Copper mode.
> 
> The 88e1510 in RGMII-to-Copper mode appears to behave correctly.
> 
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>

Applied.