netdev - Re: SFP+ support for 8168fp/8117

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Date:   Thu, 2 Jan 2020 22:24:03 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Andrew Lunn <andrew@...n.ch>, Chun-Hao Lin <hau@...ltek.com>
Cc:     Linux Netdev List <netdev@...r.kernel.org>,
        Kernel development list <linux-kernel@...r.kernel.org>,
        Anthony Wong <anthony.wong@...onical.com>,
        Jason Yen <jason.yen@...onical.com>
Subject: Re: SFP+ support for 8168fp/8117

On 02.01.2020 17:46, Kai-Heng Feng wrote:
> Hi Andrew,
> 
>> On Jan 2, 2020, at 23:21, Andrew Lunn <andrew@...n.ch> wrote:
>>
>> On Thu, Jan 02, 2020 at 02:59:42PM +0800, Kai Heng Feng wrote:
>>> Hi Heiner,
>>>
>>> There's an 8168fp/8117 chip has SFP+ port instead of RJ45, the phy device ID matches "Generic FE-GE Realtek PHY" nevertheless.
>>> The problems is that, since it uses SFP+, both BMCR and BMSR read are always zero, so Realtek phylib never knows if the link is up.
>>>
>>> However, the old method to read through MMIO correctly shows the link is up:
>>> static unsigned int rtl8169_xmii_link_ok(struct rtl8169_private *tp)
>>> {
>>>       return RTL_R8(tp, PHYstatus) & LinkStatus;
>>> }
>>>
>>> Few ideas here:
>>> - Add a link state callback for phylib like phylink's phylink_fixed_state_cb(). However there's no guarantee that other parts of this chip works.
>>> - Add SFP+ support for this chip. However the phy device matches to "Generic FE-GE Realtek PHY" which may complicate things.
>>>
>>> Any advice will be welcome.
>>
>> Hi Kai
>>
>> Is the i2c bus accessible?
> 
> I don't think so. It seems to be a regular Realtek 8168 device with generic PCI ID [10ec:8168].
> 
>> Is there any documentation or example code?
> 
> Unfortunately no.
> 
>>
>> In order to correctly support SFP+ cages, we need access to the i2c
>> bus to determine what sort of module has been inserted. It would also
>> be good to have access to LOS, transmitter disable, etc, from the SFP
>> cage.
> 
> Seems like we need Realtek to provide more information to support this chip with SFP+.
> 
Indeed it would be good to have some more details how this chip handles SFP+,
therefore I add Hau to the discussion.

As I see it the PHY registers are simply dummies on this chip. Or does this chip
support both, PHY and SFP+? Hopefully SFP presence can be autodetected, we could
skip the complete PHY handling in this case. Interesting would be which parts of
the SFP interface are exposed how via (proprietary) registers.
Recently the STMMAC driver was converted from phylib to phylink, maybe we have
to do the same with r8169 one fine day. But w/o more details this is just
speculation, much appreciated would be documentation from Realtek about the
SFP+ interface.

Kai, which hardware/board are we talking about?

> Kai-Heng
> 
>>
>>   Andrew
> 
Heiner