netdev - RE: [PATCH] e1000e: workaround missing power down mii control bit on 82571

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Message-ID: <8DD2590731AB5D4C9DBF71A877482A9001773F7655@orsmsx509.amr.corp.intel.com>
Date:	Thu, 16 Dec 2010 11:04:15 -0800
From:	"Allan, Bruce W" <bruce.w.allan@...el.com>
To:	Ben Hutchings <bhutchings@...arflare.com>,
	Arthur Jones <ajones@...erbed.com>
CC:	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] e1000e: workaround missing power down mii control bit
 on 82571

>-----Original Message-----
>From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On
>Behalf Of Ben Hutchings
>Sent: Thursday, December 16, 2010 10:57 AM
>To: Arthur Jones
>Cc: Kirsher, Jeffrey T; netdev@...r.kernel.org
>Subject: Re: [PATCH] e1000e: workaround missing power down mii control bit on
>82571
>
>On Thu, 2010-12-16 at 10:28 -0800, Arthur Jones wrote:
>> Hi Jeff,  Re-sending w/ proper netdev email
>> address.  Sorry about that...
>>
>> Arthur
>>
>> ---
>>
>> On 82571 only, AFAICT, the PHY does not seem to
>> store the MII control register 0 bit 11 (power
>> down PHY). So that when we power down the PHY
>> on dev_close() and then run ethtool on the closed
>> dev, we end up turning the PHY back on even though
>> the interface is down.  This pretty easy to repro:
>>
>> $ ethtool -s eth0 wol d
>> $ ifconfig eth0 up
>> $ mii-tool eth0
>> eth0: negotiated 100baseTx-FD, link ok
>> $ ifconfig eth0 down
>> $ mii-tool eth0
>> eth0: no link
>> $ ethtool -s eth0 autoneg on  (doesn't really matter what we do here)
>> $ mii-tool eth0
>> eth0: negotiated 100baseTx-FD, link ok (this should be: eth0: no link)
>>
>> We fix this by tracking the power down bit that we
>> write to the PHY control register and re-inserting
>> it when we read it.
>[...]
>
>Adding this special case into MDIO access seems like a really nasty
>hack.  Surely the callers that set the control register should take care
>of this.
>
>Ben.

Agreed.  I am setting up to repro now to see if it is an actual hardware
issue or just a software bug; either way, this patch is not the correct
approach and I'll follow up shortly.

Bruce.