netdev - Re: [PATCH] net phy: Check for aneg completion before setting state to PHY

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Date:	Fri, 25 Apr 2014 11:23:03 +0530
From:	Balakumaran Kannan <kumaran.4353@...il.com>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net phy: Check for aneg completion before setting state
 to PHY_RUNNING

On Fri, Apr 25, 2014 at 12:23 AM, Florian Fainelli <f.fainelli@...il.com> wrote:
> 2014-04-23 19:52 GMT-07:00 Balakumaran Kannan <kumaran.4353@...il.com>:
>> phy_state_machine should check whether auto-negotiatin is completed
>> before changing phydev->state from PHY_NOLINK to PHY_RUNNING. If
>> auto-negotiation is not completed phydev->state should be set to
>> PHY_AN.
>
> I need some time to review this. Just out of curiosity, is this fixing
> a bug you have encountered or was this found by state machine
> inspection?

Actually I encountered a problem that Linux-3.4 sends Neighbor Solicitation (NS)
before hardware completes auto-negotiation. The driver being used for
my hardware
is smsc911x.

While investigation on this, I came to know that state of phydev
follows this sequence
PHY_READY --> PHY_UP (in phy_start)
PHY_UP --> PHY_AN (in phy_start_aneg called by phy_state_machine)
PHY_AN --> PHY_NOLINK (in phy_state_machine. Link is down)
PHY_NOLINK --> PHY_RUNNING (in phy_state_machine. Link becomes ready)

So I felt that the sequence of PHY_AN --> PHY_RUNNING while link is up and
PHY_NOLINK --> PHY_RUNNING are different. In the earlier case aneg completion
is taken into account but not in later.

But this patch doesn't fix my problem. I made the smsc driver's open function to
poll on phy_aneg_done until auto-negotiation completes.

Here I have a doubt.
 * Linux network initialization and phy_state_machine runs in separate threads.
 * And driver doesn't bother about state of phydev.
Is it correct?
Doesn't driver need to confirm phydev is ready(PHY_RUNNING) before
returning to kernel?

Regards,
K.Balakumaran
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