igb: question regarding auto-negotiation

Hi

This question refers to igb codebase.
I have a question regarding the setting of hw->mac.autoneg.

Is it correct to say for igb driver:
"if speed=1000 and duplex=FULL and media_type=COPPER then only
auto-negotiate enable is supported"

i.e.
with these settings (speed/duplex/media_type) then auto-negotiate
can _not_ be disabled. Correct ?

I say this for two reasons:
1) The code in igb_set_spd_dplx() seems to indicate it:

       case SPEED_1000 + DUPLEX_FULL:
                mac->autoneg = 1;
                adapter->hw.phy.autoneg_advertised = ADVERTISE_1000_FULL;
                break;

2) Instrumenting the driver, I always see the autoneg code in e1000_check_for_copper_link_generic() get called after an igb_reset().

Have i understood correctly ?

thanks in advance
dom

If you are using copper then you are likely referring to 1000Base-T correct? If so then autonegotation is a requirement.

Here is the wikipedia URL that refers to this:
https://en.wikipedia.org/wiki/Gigabit_Ethernet#1000BASE-T

Hope this helps to clear it up.

Thanks.

- Alex

Thanks for reply. I read the wiki link and a bunch of other links besides.

So I have a follow-up question:

You're right I am using copper and 1000Base-T, and as you say auto-neg is then requirement.

So why is it possible with the igb driver to set auto-neg to OFF ?

e.g.

# ethtool -a eth6
Pause parameters for eth6:
Autonegotiate:  on
RX:             on
TX:             on

Now turn it OFF:

# ethtool -A eth6 autoneg off

# ethtool -a eth6
Pause parameters for eth6:
Autonegotiate:  off
RX:             on
TX:             on

But added debug to the driver I _know_ that it is still auto-negotiating, and printing current settings indicates 'Auto-negotiatiate' is on...

# ethtool  eth6
Settings for eth6:
         Supported ports: [ TP ]
         Supported link modes:   10baseT/Half 10baseT/Full
                                 100baseT/Half 100baseT/Full
                                 1000baseT/Full
         Supported pause frame use: No
         Supports auto-negotiation: Yes
         Advertised link modes:  10baseT/Half 10baseT/Full
                                 100baseT/Half 100baseT/Full
                                 1000baseT/Full
         Advertised pause frame use: No
         Advertised auto-negotiation: Yes
         Speed: 1000Mb/s
         Duplex: Full
         Port: Twisted Pair
         PHYAD: 1
         Transceiver: internal
         Auto-negotiation: on <<<<
         MDI-X: on
         Supports Wake-on: pumbg
         Wake-on: d
         Current message level: 0x00000007 (7)
                                drv probe link
         Link detected: yes

So I dont understand the difference between these two values ?? Can anyone help please ?

Thanks
dom

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-----Original Message-----
From: Dominic Curran [mailto:[email protected]]
Sent: Thursday, August 04, 2016 4:02 PM
To: Alexander Duyck <[email protected]>; [email protected]
Cc: Netdev <[email protected]>
Subject: Re: [E1000-devel] igb: question regarding auto-negotiation

Thanks for reply. I read the wiki link and a bunch of other links besides.

So I have a follow-up question:

You're right I am using copper and 1000Base-T, and as you say auto-neg is then requirement.

So why is it possible with the igb driver to set auto-neg to OFF ?

e.g.

# ethtool -a eth6
Pause parameters for eth6:
Autonegotiate:  on
RX:             on
TX:             on

Now turn it OFF:

# ethtool -A eth6 autoneg off

# ethtool -a eth6
Pause parameters for eth6:
Autonegotiate:  off
RX:             on
TX:             on

But added debug to the driver I _know_ that it is still auto-negotiating, and printing current settings indicates 'Auto-negotiatiate' is on...

# ethtool  eth6
Settings for eth6:
         Supported ports: [ TP ]
         Supported link modes:   10baseT/Half 10baseT/Full
                                 100baseT/Half 100baseT/Full
                                 1000baseT/Full
         Supported pause frame use: No
         Supports auto-negotiation: Yes
         Advertised link modes:  10baseT/Half 10baseT/Full
                                 100baseT/Half 100baseT/Full
                                 1000baseT/Full
         Advertised pause frame use: No
         Advertised auto-negotiation: Yes
         Speed: 1000Mb/s
         Duplex: Full
         Port: Twisted Pair
         PHYAD: 1
         Transceiver: internal
         Auto-negotiation: on <<<<
         MDI-X: on
         Supports Wake-on: pumbg
         Wake-on: d
         Current message level: 0x00000007 (7)
                                drv probe link
         Link detected: yes

So I dont understand the difference between these two values ?? Can anyone help please ?

Thanks
dom

Dom,

ethtool -A is used to set flow-control parameters, not speed/duplex/autoneg. Speed/duplex parameters are set with ethtool -s. man ethtool should help explain the difference.

I hope this helps,
Jeff
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