linux-kernel - Re: Issue with RTL8111 NIC after upgrade to kernel 4.19

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Date:   Wed, 21 Nov 2018 21:32:21 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Norbert Jurkeit <norbert.jurkeit@....de>, nic_swsd@...ltek.com,
        Florian Fainelli <f.fainelli@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        michael.wiktowy@...il.com, jcline@...hat.com,
        marc.c.dionne@...il.com
Subject: Re: Issue with RTL8111 NIC after upgrade to kernel 4.19

On 21.11.2018 21:20, Andrew Lunn wrote:
>> request_module() is supposed to be synchronous, however after some
>> reading this may not be 100% guaranteed. Maybe the module init
>> function on some systems isn't finished yet when request_module()
>> returns. As a result the genphy driver may be used instead of
>> the PHY version-specific driver.
> 
> Hi Heiner
> 
> That would be true for all PHYs i think. We would of noticed this
> problem with other systems using other PHY drivers.
> 
> 	Andrew
> 
It could be a timing issue affecting certain systems only. At least
for now I don't have a good explanation why loading the module via
request_module() and loading it upfront manually makes a difference.

One affected user just reported the PHY to be a RTL8211B. This is
what I expected, because this PHY crashes when writing to the MMD
registers (the MMD registers are used otherwise by this PHY).
See also commit 0231b1a074c6 ("net: phy: realtek: Use the dummy
stubs for MMD register access for rtl8211b").

Let's see whether the other affected systems use the same PHY
version.

Heiner