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Pause autonegotiation happens with the link partner using the same words
as the link negotiation, used for speed and duplex exchanges. However,
pause and link autonegotiation can be separately toggled :
ethtool -s eth0 autoneg on # Enable link negotiation
ethtool -A eth0 autoneg on # Enable Pause negotiation
Pause can't be negotiated if the link autoneg isn't enabled.
Pause autoneg and link autoneg settings must not interfere with one
another when user is configuring them :
- If Pause autoneg is on, it must stay on when link autoneg is disabled
(even though Pause won't actually be negotiated)
- If Pause autoneg is off, it must stay off when link autoneg is
enabled
Introduce a set of tests to verify that pause and link autoneg are
behaving correctly, in particular that the user intent is correctly
cached when toggling link autoneg.
Signed-off-by: Maxime Chevallier (Netdev Foundation) <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20261015134350.629593-4-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Ethernet flow control is a tricky thing to get right, especially when it
comes to correctly handling the negotiation of the parameters with a
link partner.
On one hand, the userspace API talks in terms of the device's ability to
send Pause frames when the device is overwhelmed by ingress traffic (TX
pause) and the ability to stop sending traffic upon receiving Pause
frames (RX pause).
On the other hand, 802.3 explains that devices can exchange their
abilities over link negotiation, but instead of echanging TX and RX
abilities, they exchange Pause and Asymmetric Pause capabilities :
RX unable TX unable => None
RX able TX unable => Pause + Asymmetric
RX unable TX able => Asymmetric
RX able TX able => Pause
The reported Pause and Asym abilities depend both on the MAC, that
eventually sends and processes these frames, and the PHY, that
advertises these to the partner.
Both MAC and PHYs can have their own limitations, and getting the
correct set of supported Pause/Asym parameters is non-trivial, unless
the MAC uses phylink, which deals with the complexity.
Introduce a set of Pause selftests that verify that the local
interface's supported pause parameters reported from ethtool (in terms
of Pause + Asym ) match the accepted parameters from "ethtool -A",
corresponding to ethtool's .set_pauseparams() ops, expressed in TX and
RX abilities.
Signed-off-by: Maxime Chevallier (Netdev Foundation) <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20261015134350.629593-2-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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