netdev - Re: [RFC PATCH v1] net: ethernet: nb8800: Reset HW block in ndo

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Message-ID: <yw1x379fla7r.fsf@mansr.com>
Date:   Sat, 29 Jul 2017 13:05:28 +0100
From:   Måns Rullgård <mans@...sr.com>
To:     Mason <slash.tmp@...e.fr>
Cc:     Marc Gonzalez <marc_gonzalez@...madesigns.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v1] net: ethernet: nb8800: Reset HW block in ndo_open

Mason <slash.tmp@...e.fr> writes:

> On 29/07/2017 13:24, Måns Rullgård wrote:
>
>> Until you figure out why it's getting stuck, we can't be sure
>> it isn't caused by something that could trigger at any time.
> Would you take a look at it, if I can reproduce on tango4?
>
> I have identified a 100% reproducible flaw.
> I have proposed a work-around that brings this down to 0
> (tested 1000 cycles of link up / ping / link down).
>
> In my opinion, upstream should consider this work-around
> for inclusion. I'd like to hear David's and Florian's
> opinion on the topic. It's always a pain to maintain
> out-of-tree patches.

I'm not saying it shouldn't be fixed.  I am saying we should make sure
we make the right fix, not just paper over one instance of a wider issue.

>> Yes, but by then you've reset those parameters to the defaults.
>
> Good catch. There is some non HW-related init in
> nb8800_hw_init().
>
> I'll take this opportunity to change flow control to
> off by default (it breaks several 100 Mbps switches).

I was told to have it on by default.  This is what most other drivers do
too.  If you have faulty switches, that's your problem.

-- 
Måns Rullgård