netdev - Re: [PATCH net-next 4/4] net: dsa: Do not clobber PHY link outside of state machine

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Message-ID: <20170207131440.GF31560@lunn.ch>
Date:   Tue, 7 Feb 2017 14:14:40 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "zefir.kurtisi@...atec.com" <zefir.kurtisi@...atec.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Wingman Kwok <w-kwok2@...com>,
        Murali Karicheri <m-karicheri2@...com>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Philippe Reynes <tremyfr@...il.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Jisheng Zhang <jszhang@...vell.com>,
        Jarod Wilson <jarod@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 4/4] net: dsa: Do not clobber PHY link outside
 of state machine

> Related is that polling the phy status every second can be bad news for
> system latency.
> Typically it involves bit-bashing an interface with spin-delays to
> meet the slow timings (with extra delays to allow for posted writes).
> An alternative would be to do a very slow bit-bang on each timer tick,
> this would need to be sped up and finished before any other actions.

Or just use PHY interrupts. That completely stops the MDIO polling.

   Andrew