netdev - Re: [PATCH net-next] net: sfp: add some quirks for FreeTel direct attach modules

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Date:   Fri, 8 May 2020 18:27:06 +0200
From:   Marek Behun <marek.behun@....cz>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: sfp: add some quirks for FreeTel direct
 attach modules

On Fri, 8 May 2020 16:28:44 +0100
Russell King - ARM Linux admin <linux@...linux.org.uk> wrote:

> On Thu, May 07, 2020 at 03:21:35PM +0200, Marek Behún wrote:
> > FreeTel P.C30.2 and P.C30.3 may fail to report anything useful from
> > their EEPROM. They report correct nominal bitrate of 10300 MBd, but do
> > not report sfp_ct_passive nor sfp_ct_active in their ERPROM.
> > 
> > These modules can also operate at 1000baseX and 2500baseX.
> > 
> > Signed-off-by: Marek Behún <marek.behun@....cz>
> > Cc: Russell King <rmk+kernel@...linux.org.uk>
> > ---
> >  drivers/net/phy/sfp-bus.c | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > 
> > diff --git a/drivers/net/phy/sfp-bus.c b/drivers/net/phy/sfp-bus.c
> > index 6900c68260e0..f021709bedcc 100644
> > --- a/drivers/net/phy/sfp-bus.c
> > +++ b/drivers/net/phy/sfp-bus.c
> > @@ -44,6 +44,14 @@ static void sfp_quirk_2500basex(const struct sfp_eeprom_id *id,
> >  	phylink_set(modes, 2500baseX_Full);
> >  }
> >  
> > +static void sfp_quirk_direct_attach_10g(const struct sfp_eeprom_id *id,
> > +					unsigned long *modes)
> > +{
> > +	phylink_set(modes, 10000baseCR_Full);
> > +	phylink_set(modes, 2500baseX_Full);
> > +	phylink_set(modes, 1000baseX_Full);
> > +}
> > +
> >  static const struct sfp_quirk sfp_quirks[] = {
> >  	{
> >  		// Alcatel Lucent G-010S-P can operate at 2500base-X, but
> > @@ -63,6 +71,18 @@ static const struct sfp_quirk sfp_quirks[] = {
> >  		.vendor = "HUAWEI",
> >  		.part = "MA5671A",
> >  		.modes = sfp_quirk_2500basex,
> > +	}, {
> > +		// FreeTel P.C30.2 is a SFP+ direct attach that can operate at
> > +		// at 1000baseX, 2500baseX and 10000baseCR, but may report none
> > +		// of these in their EEPROM
> > +		.vendor = "FreeTel",
> > +		.part = "P.C30.2",
> > +		.modes = sfp_quirk_direct_attach_10g,
> > +	}, {
> > +		// same as previous
> > +		.vendor = "FreeTel",
> > +		.part = "P.C30.3",
> > +		.modes = sfp_quirk_direct_attach_10g,  
> 
> Looking at the EEPROM capabilities, it seems that these modules give
> either:
> 
> Transceiver codes     : 0x01 0x00 0x00 0x00 0x00 0x04 0x80 0x00 0x00
> Transceiver type      : Infiniband: 1X Copper Passive
> Transceiver type      : Passive Cable
> Transceiver type      : FC: Twin Axial Pair (TW)
> Encoding              : 0x06 (64B/66B)
> BR, Nominal           : 10300MBd
> Passive Cu cmplnce.   : 0x01 (SFF-8431 appendix E) [SFF-8472 rev10.4 only]
> BR margin, max        : 0%
> BR margin, min        : 0%
> 
> or:
> 
> Transceiver codes     : 0x00 0x00 0x00 0x00 0x00 0x04 0x80 0x00 0x00
> Transceiver type      : Passive Cable
> Transceiver type      : FC: Twin Axial Pair (TW)
> Encoding              : 0x06 (64B/66B)
> BR, Nominal           : 10300MBd
> Passive Cu cmplnce.   : 0x01 (SFF-8431 appendix E) [SFF-8472 rev10.4 only]
> BR margin, max        : 0%
> BR margin, min        : 0%
> 
> These give ethtool capability mask of 000,00000600,0000e040, which
> is:
> 
> 	2500baseX (bit 15)
> 	1000baseX (bit 41)
> 	10000baseCR (bit 42)
> 
> 10000baseCR, 2500baseX and 1000baseX comes from:
> 
>         if ((id->base.sfp_ct_passive || id->base.sfp_ct_active) && br_nom) {
>                 /* This may look odd, but some manufacturers use 12000MBd */
>                 if (br_min <= 12000 && br_max >= 10300)
>                         phylink_set(modes, 10000baseCR_Full);
>                 if (br_min <= 3200 && br_max >= 3100)
>                         phylink_set(modes, 2500baseX_Full);
>                 if (br_min <= 1300 && br_max >= 1200)
>                         phylink_set(modes, 1000baseX_Full);
> 
> since id->base.sfp_ct_passive is true, and br_nom = br_max = 10300 and
> br_min = 0.
> 
> 10000baseCR will also come from:
> 
>         if (id->base.sfp_ct_passive) {
>                 if (id->base.passive.sff8431_app_e)
>                         phylink_set(modes, 10000baseCR_Full);
>         }
> 
> You claimed in your patch description that sfp_ct_passive is not set,
> but the EEPROM dumps contain:
> 
> 	Transceiver type      : Passive Cable
> 
> which is correctly parsed by the kernel.
> 
> So, I'm rather confused, and I don't see why this patch is needed.
> 

Russell,

something is wrong here, and it is my bad. I hope I didn't mix
the EEPROM images from when I was playing with the contents, but it
seems possible now :( I probably sent you modified images and lost the
original ones.

The thing I know for sure is that it did not work when I got the
cables and also that they had different contents inside - ie at least
one side of one cable did not report ct_passive nor ct_active. And I
think that they reported different things on each side.

I will try to get another such cable and return to this.

Marek