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

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Message-ID: <20101216200425.GO18990@ajones-laptop.nbttech.com>
Date:	Thu, 16 Dec 2010 12:04:26 -0800
From:	Arthur Jones <arthur.jones@...erbed.com>
To:	"Allan, Bruce W" <bruce.w.allan@...el.com>
CC:	Ben Hutchings <bhutchings@...arflare.com>,
	"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

Hi Bruce, ...

On Thu, Dec 16, 2010 at 11:28:18AM -0800, Allan, Bruce W wrote:
> >-----Original Message-----
> >From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On
> >Behalf Of Allan, Bruce W
> >Sent: Thursday, December 16, 2010 11:04 AM
> >To: Ben Hutchings; Arthur Jones
> >Cc: Kirsher, Jeffrey T; 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
> >>
> >>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.
> 
> It's the reset in e1000_set_settings() which ignores that we had previously
> powered off the Phy.  I'll go through the rest of the code and fix up this
> and any other occurrences of similar issues properly.

Thanks for having a look!

We do a read-modify-write there of
the PHY control register.  We take
the rest of the bits as being good,
but, for some reason we don't get the
power down bit (always reads back
zero).  Is this a known 82571 issue?
On 82574, e.g., we seem to get the
power down bit back when we read...

Are you sure you want to spread that
82571 specific logic all over the driver?

Arthur

> 
> Thanks for reporting this issue Arthur.
> 
> Bruce.
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