[PATCH net-next] net: sfp: Add quirk for Dell M14MK module

Greetings,

This adds an quirk for the Dell M14MK (S28-10G-25G-SR-85C) SFP28 module.
These are short range fiber modules, and should advertise 10000baseSR/Full.
Incorrectly these advertise as being a copper module: 10000baseCR/Full. 
The link fails to come up, and the kernel logs "unsupported SFP module: 
no common interface modes."
With the quirk added, the 10Gbit/s link comes up.

Tested on a Linksys LGS328PC with OpenWRT SNAPSHOT version:
OpenWrt SNAPSHOT r35298-2a73f02e56 / LuCI Master 26.190.71895~a18dc50.
Ethtool advertises now "10000baseSR/Full" and the link works on 10Gbit/s.

Thank you for your time.

Kind regards,

Xander Wilmink

Co-authored-by: Jonas Jelonek <[email protected]>
Signed-off-by: Xander Wilmink <[email protected]>

---
 drivers/net/phy/sfp.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 6c25b73c668a..64b4ec08f28a 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -477,6 +477,13 @@ static void sfp_quirk_2500basex(const struct sfp_eeprom_id *id,
 	__set_bit(PHY_INTERFACE_MODE_2500BASEX, caps->interfaces);
 }
 
+static void sfp_quirk_25g_10g_dual(const struct sfp_eeprom_id *id,
+				   struct sfp_module_caps *caps)
+{
+	linkmode_set_bit(ETHTOOL_LINK_MODE_10000baseSR_Full_BIT,
+			 caps->link_modes);
+	__set_bit(PHY_INTERFACE_MODE_10GBASER, caps->interfaces);
+
 static void sfp_quirk_disable_autoneg(const struct sfp_eeprom_id *id,
 				      struct sfp_module_caps *caps)
 {
@@ -523,6 +530,10 @@ static const struct sfp_quirk sfp_quirks[] = {
 	SFP_QUIRK("ALCATELLUCENT", "G010SP", sfp_quirk_2500basex,
 		  sfp_fixup_ignore_tx_fault),
 
+	// Dell M14MK, 10/25 GBit SFP28 module. Labeled as Dell S28-10G-25G-SR-85C.
+	// Runs at 10 Gbit/s in a SFP+ port, but does not advertise this properly.
+	SFP_QUIRK_S("DELL", "M14MK", sfp_quirk_25g_10g_dual),
+
 	// Alcatel Lucent G-010S-A can operate at 2500base-X, but report 3.2GBd
 	// NRZ in their EEPROM
 	SFP_QUIRK("ALCATELLUCENT", "3FE46541AA", sfp_quirk_2500basex,
-- 
2.52.0