netdev - Re: [drivers/net/phy/sfp] intermittent failure in state machine checks

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Date:   Fri, 10 Jan 2020 17:08:36 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     ѽ҉ᶬḳ℠ <vtol@....net>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: [drivers/net/phy/sfp] intermittent failure in state machine
 checks

On Fri, Jan 10, 2020 at 04:53:06PM +0000, ѽ҉ᶬḳ℠ wrote:
> Seems that the debug avenue has been exhausted, short of running SFP.C in
> debug mode.

You're saying you never see TX_FAULT asserted other than when the
interface is down?

> There is still no explanation why the module passes the 300 ms deassert
> TX_FAULT test most of the time but fails intermittently at other times,
> being kind of incoherent. Maybe it is just wishful thinking but it seems a
> bit far-fetched that the module is really causing this, least the readings
> from GPIO do not provide any such indicator.
> 
> Could there be something choking / blocking the communication channel
> between the module and the kernel, some kernel code getting stuck / leaked
> in memory?

There is no "communication channel" involved here.  It is just those
GPIOs.

> Could the ipupdown routine, which has its own implementation in OpenWrt, be
> an interfering agent, e.g. the way it constructs or tears down the iif,
> though I do not see how?

Very unlikely.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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