netdev - Re: [PATCH net-next 2/2] net: sfp: add quirk for 2.5G copper SFP

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Date:   Sat, 25 Mar 2023 19:36:10 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 2/2] net: sfp: add quirk for 2.5G copper SFP

On Sat, Mar 25, 2023 at 03:35:01PM +0000, Daniel Golle wrote:
> On Sat, Mar 25, 2023 at 02:05:51PM +0000, Russell King (Oracle) wrote:
> > On Sat, Mar 25, 2023 at 02:12:16AM +0000, Daniel Golle wrote:
> > > Hi Russell,
> > > 
> > > On Tue, Mar 21, 2023 at 04:58:51PM +0000, Russell King (Oracle) wrote:
> > > > Add a quirk for a copper SFP that identifies itself as "OEM"
> > > > "SFP-2.5G-T". This module's PHY is inaccessible, and can only run
> > > > at 2500base-X with the host without negotiation. Add a quirk to
> > > > enable the 2500base-X interface mode with 2500base-T support, and
> > > > disable autonegotiation.
> > > > 
> > > > Reported-by: Frank Wunderlich <frank-w@...lic-files.de>
> > > > Tested-by: Frank Wunderlich <frank-w@...lic-files.de>
> > > > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> > > 
> > > I've tried the same fix also with my 2500Base-T SFP module:
> > > diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
> > > index 4223c9fa6902..c7a18a72d2c5 100644
> > > --- a/drivers/net/phy/sfp.c
> > > +++ b/drivers/net/phy/sfp.c
> > > @@ -424,6 +424,7 @@ static const struct sfp_quirk sfp_quirks[] = {
> > >         SFP_QUIRK_F("Turris", "RTSFP-10", sfp_fixup_rollball),
> > >         SFP_QUIRK_F("Turris", "RTSFP-10G", sfp_fixup_rollball),
> > >         SFP_QUIRK_F("OEM", "SFP-GE-T", sfp_fixup_ignore_tx_fault),
> > > +       SFP_QUIRK_M("TP-LINK", "TL-SM410U", sfp_quirk_oem_2_5g),
> > >  };
> > > 
> > >  static size_t sfp_strlen(const char *str, size_t maxlen)
> > 
> > Thanks for testing.
> > 
> > > However, the results are a bit of a mixed bag. The link now does come up
> > > without having to manually disable autonegotiation. However, I see this
> > > new warning in the bootlog:
> > > [   17.344155] sfp sfp2: module TP-LINK          TL-SM410U        rev 1.0  sn 12154J6000864    dc 210606  
> > > ...
> > > [   21.653812] mt7530 mdio-bus:1f sfp2: selection of interface failed, advertisement 00,00000000,00000000,00006440
> > 
> > This will be the result of issuing an ethtool command, and phylink
> > doesn't know what to do with the advertising mask - which is saying:
> > 
> >    Autoneg, Fibre, Pause, AsymPause
> > 
> > In other words, there are no capabilities to be advertised, which is
> > invalid, and suggests user error. What ethtool command was being
> > issued?
> 
> This was simply adding the interface to a bridge and bringing it up.
> No ethtool involved afaik.

If its not ethtool, then there is only one other possibility which I
thought had already been ruled out - and that is the PHY is actually
accessible, but either we don't have a driver for it, or when reading
the PHY's "features" we don't know what it is.

Therefore, as the PHY is accessible, we need to identify what it is
and have a driver for it.

Please apply the following patch to print some useful information
about the PHY:

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index aec8e48bdd4f..6b67262d5706 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -2978,9 +2978,37 @@ static int phylink_sfp_config_phy(struct phylink *pl, u8 mode,
 
 	iface = sfp_select_interface(pl->sfp_bus, config.advertising);
 	if (iface == PHY_INTERFACE_MODE_NA) {
+		const int num_ids = ARRAY_SIZE(phy->c45_ids.device_ids);
+		u32 id;
+		int i;
+
+		if (phy->is_c45) {
+			for (i = 0; i < num_ids; i++) {
+				id = phy->c45_ids.device_ids[i];
+				if (id != 0xffffffff)
+					break;
+			}
+		} else {
+			id = phy->phy_id;
+		}
+		phylink_err(pl,
+			    "Clause %s PHY [0x%04x:0x%04x] driver %s found but\n",
+			    phy->is_c45 ? "45" : "22",
+			    id >> 16, id & 0xffff,
+			    phy->drv ? phy->drv->name : "[unbound]");
 		phylink_err(pl,
 			    "selection of interface failed, advertisement %*pb\n",
 			    __ETHTOOL_LINK_MODE_MASK_NBITS, config.advertising);
+
+		if (phy->is_c45) {
+			phylink_err(pl, "Further PHY IDs:\n");
+			for (i = 0; i < num_ids; i++) {
+				id = phy->c45_ids.device_ids[i];
+				if (id != 0xffffffff)
+					phylink_err(pl, "  MMD %d [0x%04x:0x%04x]\n",
+						    i, id >> 16, id & 0xffff);
+			}
+		}
 		return -EINVAL;
 	}
 

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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