netdev - Re: [PATCH net 2/2] net: phylink: Force retrigger in case of latched link-fail indicator

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Message-ID: <YZzOwfkkdDVHr+jc@shell.armlinux.org.uk>
Date:   Tue, 23 Nov 2021 11:21:37 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Marek Behún <kabel@...nel.org>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Andrew Lunn <andrew@...n.ch>, davem@...emloft.net
Subject: Re: [PATCH net 2/2] net: phylink: Force retrigger in case of latched
 link-fail indicator

On Tue, Nov 23, 2021 at 12:51:54AM +0100, Marek Behún wrote:
> On mv88e6xxx 1G/2.5G PCS, the SerDes register 4.2001.2 has the following
> description:
>   This register bit indicates when link was lost since the last
>   read. For the current link status, read this register
>   back-to-back.
> 
> Thus to get current link state, we need to read the register twice.
> 
> But doing that in the link change interrupt handler would lead to
> potentially ignoring link down events, which we really want to avoid.
> 
> Thus this needs to be solved in phylink's resolve, by retriggering
> another resolve in the event when PCS reports link down and previous
> link was up.
> 
> The wrong value is read when phylink requests change from sgmii to
> 2500base-x mode, and link won't come up. This fixes the bug.
> 
> Fixes: 9525ae83959b ("phylink: add phylink infrastructure")
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> Signed-off-by: Marek Behún <kabel@...nel.org>

Same issue with this patch wrt authorship vs sign-off.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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