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

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Date:   Fri, 13 Jan 2023 23:28:14 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Hau <hau@...ltek.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>
Subject: Re: [PATCH net] r8169: fix rtl8168h wol fail

On 13.01.2023 17:36, Andrew Lunn wrote:
> On Fri, Jan 13, 2023 at 04:23:45PM +0000, Hau wrote:
>>>>>>> In this application(rtl8168h + rtl8211fs) it also supports 100Mbps
>>>>>>> fiber
>>>>>> module.
>>>>>>
>>>>>> Does RTL8211FS advertise 100Mbps and 1Gbps on the UTP/MDI side in
>>>>>> case of a 100Mbps fiber module?
>>>>> Yes.
>>>>>
>>>> I think in this case internal PHY and RTL8211FS would negotiate 1Gbps,
>>>> not matching the speed of the 100Mbps fiber module.
>>>> How does this work?
>>
>> My mistake. With 100Mbps fiber module RTL8211FS will only advertise 100Mbps
>> on the UTP/MDI side. With 1Gbps fiber module it will advertise both 100Mbps and
>> 1Gbps. So issue will only happen with 1Gbps fiber module.
>>
>>> Fibre line side has no autoneg. Both ends need to be using the same speed,
>>> or the SERDES does not synchronise and does not establish link.
>>>
>>> You can ask the SFP module what baud rate it supports, and then use
>>> anything up to that baud rate. I've got systems where the SFP is fast enough
>>> to support a 2.5Gbps link, so the MAC indicates both 2.5G and 1G, defaults to
>>> 2.5G, and fails to connect to a 1G link peer. You need to use ethtool to force
>>> it to the lower speed before the link works.
>>>
>>> But from what i understand, you cannot use a 1000Base-X SFP, set the MAC
>>> to 100Mbps, and expect it to connect to a 100Base-FX SFP. So for me, the
>>> RTL8211FS should not be advertise 100Mbps and 1Gbps, it needs to talk to
>>> the SFP figure out exactly what it is, and only advertise the one mode which
>>> is supported.
>>
>> It is the RTL8211FS firmware bug. This patch is for workaround this issue.
> 
> So if it is advertising both 100Mbps and 1Gbps, we know the SFP is
> actually 1G, and we can remove the 100Mbps advertisement? That should
> then solve all the problems?
> 
Right, that's what I proposed too, removing 1Gbps advertisement of the
RTL8168H-internal PHY via userspace tool, e.g. ethtool. For me this is
the cleanest solution. Adding a workaround for a firmware bug of a
specific external PHY to the r8169 MAC driver would be somewhat hacky.




>      Andrew