netdev - Re: net: phylink: dsa: mv88e6xxx: flaky link detection on switch ports with internal PHYs

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Date:   Fri, 25 Jan 2019 11:30:54 -0500
From:   John David Anglin <dave.anglin@...l.net>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Russell King <linux@....linux.org.uk>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: net: phylink: dsa: mv88e6xxx: flaky link detection on switch
 ports with internal PHYs

On 2019-01-22 7:22 p.m., Andrew Lunn wrote:
> >From my Espressobin
>
> cat /proc/interrupts
> ...
>  44:          0          0  mv88e6xxx-g1   3 Edge      mv88e6xxx-g1-atu-prob
>  46:          0          0  mv88e6xxx-g1   5 Edge      mv88e6xxx-g1-vtu-prob
>  48:         38         24  mv88e6xxx-g1   7 Edge      mv88e6xxx-g2
>  51:          0          1  mv88e6xxx-g2   1 Edge      !soc!internal-regs@...00000!mdio@...04!switch0@...dio:11
>  52:          0          0  mv88e6xxx-g2   2 Edge      !soc!internal-regs@...00000!mdio@...04!switch0@...dio:12
>  53:         38         23  mv88e6xxx-g2   3 Edge      !soc!internal-regs@...00000!mdio@...04!switch0@...dio:13
>
> These are PHY interrupts.
>
Thanks.  That was the clue.  I had tried to enable hardware for support
for switch interrupts.  However,
the espressobin connects the switch interrupt output to a southbridge
pin that only supports edge interrupts.
Link detection works okay once the attached change is removed.  I may
try and see if moving the interrupt
to a northbridge pin works.

I have to wonder about the use of edge interrupts.  Given that a GPIO
interrupt isn't defined for the mv88e6xxx,
then the interrupt must be done by polling the global1 control register.

This also makes me wonder about this SD interrupt:
43:          0          0     GPIO1   3 Edge      d00d0000.sdhci cd
Many poeple have trouble with SD cards on reboot.

Although the driver doesn't handle AVB interrupts, I started down this
path to try get ptp4l working better.  I
have tweaked the polling but there are still circumstances where
timestamps are overwritten (or not written).

Dave

-- 
John David Anglin  dave.anglin@...l.net


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