netdev - Re: [PATCH 2/2] at803x: double check SGMII side autoneg

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Date:   Wed, 24 May 2017 15:57:06 -0500
From:   Timur Tabi <timur@....qualcomm.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Matthias May <matthias.may@...atec.com>,
        Zefir Kurtisi <zefir.kurtisi@...atec.com>,
        <netdev@...r.kernel.org>, <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        Manoj Iyer <manoj.iyer@...onical.com>, <jhugo@...eaurora.org>
Subject: Re: [PATCH 2/2] at803x: double check SGMII side autoneg

On 05/24/2017 02:34 PM, Andrew Lunn wrote:
>> Ok, I'm going to debug this some more.  It turns out that the MAC side of
>> the SGMII link can send an interrupt when it thinks that auto-negotiation is
>> done.  I might be able to use this.
>
> You can use this for your board. But it still leaves the phy driver
> broken for everybody else.

Wait, I thought you said the at803x driver was not broken, since it 
returns 0 when the SGMII side of the link hasn't finished auto-negotiating?

>> What function should my MAC driver call when it wants the phy core to call
>> at803x_aneg_done again to see if autonegotiation is done?
>
> You want to trigger the PHY state machine. There is only one exported
> API call to do this, phy_mac_interrupt(). But you are supposed to pass
> the new link state. And your MAC driver has no idea of that, it does
> not know if the copper side of the PHY is up.

My NIC has a feature called autopolling where it takes over the MDIO bus 
and regularly polls the link state.  When it detects that the link state 
has changed, it generates a MAC interrupt.  This is when I call 
phy_mac_interrupt() normally.

I think I can use the SGMII interrupt to also call phy_mac_interrupt(). 
The problem is the from the copper side, the link is already up, so if I 
call phy_mac_interrupt() again and say the link is up, the phy core is 
going to ignore that.

> So it might be better if you export phy_trigger_machine().

I'll test that, but that does seem a bit hackish.

>> Also, is there a way for the MAC driver to know that at803x_aneg_done()
>> previously returned 0, and that it needs to tell the phy core to check again?
>
> Not that i know of. The MAC layer is not supposed to be messing around
> in the PHY layer. However, just triggering the PHY state machine
> should be enough.

Can you tell my how PHY_HAS_INTERRUPT is supposed to work?  How does the 
PHY send an interrupt?

I'm starting to think that my NIC's autopolling feature is not 
compatible with phylib, and that I should use polling mode.