netdev - Re: [PATCH v2 net-next 1/3] net: phy: check that PHY is stopped when entering phy

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Date:   Thu, 17 Jan 2019 07:19:44 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net-next 1/3] net: phy: check that PHY is stopped when
 entering phy_disconnect

On 16.01.2019 22:48, Andrew Lunn wrote:
> On Wed, Jan 16, 2019 at 09:25:15PM +0100, Heiner Kallweit wrote:
>> Every driver should have called phy_stop() before calling
>> phy_disconnect(). Let's check for this and ensure PHY is stopped
>> when starting with the actual work in phy_disconnect().
> 
> Hi Heiner
> 
> Looking at the patch, i think why must the MAC driver call phy_stop()
> before phy_disconnect()? It keeps is symmetrical, you need
> phy_connect() and then phy_start(). But if the core can detect that
> phy_stop() has not been called, and can call phy_stop() when needed,
> we can probably simplify the MAC drivers by removing many of the
> phy_stop() calls.
> 
> I think it might come down to where the phy_connect()/phy_disconnect()
> is performed. Sometimes it is in probe()/remove(), sometimes it is in
> open()/close(). If phy_disconnect() is in remove(), phy_stop() is
> needed in close(). But if phy_disconnect() is called in close() the
> phy_stop() could be skipped?
> 
Right, there may be cases where this is possible. However typically I
see the following in network drivers in close():
- first different things are stopped / cleaned up, where order is
  critical (stopping PHY, tx queues, ..)
- then resources are released (free interrupt, ..)
Therefore I assume that in most cases the split to phy_stop() and
phy_disconnect() is needed.

> Before we start adding warning, we probably should first document the
> expectations. Documentation/networking/phy.txt seems like a good
> place.
> 
Indeed, that's something we should do.

> 	Andrew
> 
Heiner