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Documentation: net: phy: Add a paragraph about pause frames/flow control

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Describe that the Ethernet MAC controller is ultimately responsible for
dealing with proper pause frames/flow control advertisement and
enabling, and that it is therefore allowed to have it change
phydev->supported/advertising with SUPPORTED_Pause and
SUPPORTED_AsymPause.

Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Fainelli 2016-11-27 18:45:13 -08:00 committed by David S. Miller
parent 527fd70e26
commit 2fa3e25b45
1 changed files with 16 additions and 2 deletions
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18
Documentation/networking/phy.txt
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@ -127,8 +127,9 @@ Letting the PHY Abstraction Layer do Everything
values pruned from them which don't make sense for your controller (a 10/100
controller may be connected to a gigabit capable PHY, so you would need to
mask off SUPPORTED_1000baseT*). See include/linux/ethtool.h for definitions
for these bitfields. Note that you should not SET any bits, or the PHY may
get put into an unsupported state.
for these bitfields. Note that you should not SET any bits, except the
SUPPORTED_Pause and SUPPORTED_AsymPause bits (see below), or the PHY may get
put into an unsupported state.
Lastly, once the controller is ready to handle network traffic, you call
phy_start(phydev). This tells the PAL that you are ready, and configures the
@ -139,6 +140,19 @@ Letting the PHY Abstraction Layer do Everything
When you want to disconnect from the network (even if just briefly), you call
phy_stop(phydev).
Pause frames / flow control
The PHY does not participate directly in flow control/pause frames except by
making sure that the SUPPORTED_Pause and SUPPORTED_AsymPause bits are set in
MII_ADVERTISE to indicate towards the link partner that the Ethernet MAC
controller supports such a thing. Since flow control/pause frames generation
involves the Ethernet MAC driver, it is recommended that this driver takes care
of properly indicating advertisement and support for such features by setting
the SUPPORTED_Pause and SUPPORTED_AsymPause bits accordingly. This can be done
either before or after phy_connect() and/or as a result of implementing the
ethtool::set_pauseparam feature.
Keeping Close Tabs on the PAL
It is possible that the PAL's built-in state machine needs a little help to