ixgbe: Document how to enable NBASE-T support

Commit a296d665ea ("ixgbe: Add ethtool support to enable 2.5 and 5.0
Gbps support") introduced suppression of the advertisement of NBASE-T
speeds by default, according to Todd Fujinaka to accommodate customers
with network switches which could not cope with advertised NBASE-T
speeds, as posted in the E1000-devel mailing list:

https://sourceforge.net/p/e1000/mailman/message/37106269/

However, the suppression was not documented at all, nor was how to
enable NBASE-T support.

Properly document the NBASE-T suppression and how to enable NBASE-T
support.

Fixes: a296d665ea ("ixgbe: Add ethtool support to enable 2.5 and 5.0 Gbps support")
Reported-by: Robert Schlabbach <robert_s@gmx.net>
Signed-off-by: Robert Schlabbach <robert_s@gmx.net>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
This commit is contained in:
Robert Schlabbach 2021-10-26 02:24:48 +02:00 committed by Tony Nguyen
parent 0182d1f3fa
commit 271225fd57
2 changed files with 20 additions and 0 deletions

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@ -440,6 +440,22 @@ NOTE: For 82599-based network connections, if you are enabling jumbo frames in
a virtual function (VF), jumbo frames must first be enabled in the physical
function (PF). The VF MTU setting cannot be larger than the PF MTU.
NBASE-T Support
---------------
The ixgbe driver supports NBASE-T on some devices. However, the advertisement
of NBASE-T speeds is suppressed by default, to accommodate broken network
switches which cannot cope with advertised NBASE-T speeds. Use the ethtool
command to enable advertising NBASE-T speeds on devices which support it::
ethtool -s eth? advertise 0x1800000001028
On Linux systems with INTERFACES(5), this can be specified as a pre-up command
in /etc/network/interfaces so that the interface is always brought up with
NBASE-T support, e.g.::
iface eth? inet dhcp
pre-up ethtool -s eth? advertise 0x1800000001028 || true
Generic Receive Offload, aka GRO
--------------------------------
The driver supports the in-kernel software implementation of GRO. GRO has

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@ -5531,6 +5531,10 @@ static int ixgbe_non_sfp_link_config(struct ixgbe_hw *hw)
if (!speed && hw->mac.ops.get_link_capabilities) {
ret = hw->mac.ops.get_link_capabilities(hw, &speed,
&autoneg);
/* remove NBASE-T speeds from default autonegotiation
* to accommodate broken network switches in the field
* which cannot cope with advertised NBASE-T speeds
*/
speed &= ~(IXGBE_LINK_SPEED_5GB_FULL |
IXGBE_LINK_SPEED_2_5GB_FULL);
}