netdev - Re: [PATCH net] r8169: fix rtl8168h wol fail

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Message-ID: <4014d243-8f8a-f273-fba8-2ae5a3844ea5@gmail.com>
Date:   Fri, 6 Jan 2023 19:40:45 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Hau <hau@...ltek.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>, Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH net] r8169: fix rtl8168h wol fail

On 06.01.2023 07:53, Hau wrote:
>>>> rtl8168h has an application that it will connect to rtl8211fs
>>>> through mdi interface. And rtl8211fs will connect to fiber through serdes
>> interface.
>>>> In this application, rtl8168h revision id will be set to 0x2a.
>>>>
>>>> Because rtl8211fs's firmware will set link capability to 100M and
>>>> GIGA when link is from off to on. So when system suspend and wol is
>>>> enabled, rtl8168h will speed down to 100M (because rtl8211fs
>>>> advertise 100M and GIGA to rtl8168h). If the link speed between
>> rtl81211fs and fiber is GIGA.
>>>> The link speed between rtl8168h and fiber will mismatch. That will
>>>> cause wol fail.
>>>>
>>>> In this patch, if rtl8168h is in this kind of application, driver
>>>> will not speed down phy when wol is enabled.
>>>>
>>> I think the patch title is inappropriate because WoL works normally on
>>> RTL8168h in the standard setup.
>>> What you add isn't a fix but a workaround for a firmware bug in RTL8211FS.
>>> As mentioned in a previous review comment: if speed on fibre side is
>>> 1Gbps then RTL8211FS shouldn't advertise 100Mbps on MDI/UTP side.
>>> Last but not least the user can still use e.g. ethtool to change the
>>> speed to 100Mbps thus breaking the link.
>>
>> I agree with Heiner here. I assume you cannot fix the firmware?
>>
>> So can we detect the broken firmware and correctly set
>> phydev->advertising? That will fix WoL and should prevent the user
>> from using ethtool to select a slower speed.
>>
> It is a rtl8211fs's firmware bug. Because in this application it will support both 100M and GIGA
> fiber module, so it cannot just set phydev->advertising to 100M or GIGA. We  may need to 
> use bit-bang MDIO to detect fiber link speed and set phydev->advertising properly. But it will
> let this patch become more complicated.
> 
I think there's also a userspace workaround for your problem.
You can use "ethtool -s <if> advertise .." to adjust what the internal PHY advertises.
phy_speed_down() considers only modes that are currently advertised.

In your case with a 1Gbps fibre module you could set the advertisement to 1Gbps/full only.
Then phy_speed_down() wouldn't change the speed.