linux-kernel - Re: [PATCH net-next v2 1/2] net: dsa: mv88e6xxx: Save switch rules

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Date:   Fri, 1 Feb 2019 12:01:19 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Vivien Didelot <vivien.didelot@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Nadav Haklai <nadavh@...vell.com>
Subject: Re: [PATCH net-next v2 1/2] net: dsa: mv88e6xxx: Save switch rules

Hi Vivien,

Vivien Didelot <vivien.didelot@...il.com> wrote on Wed, 30 Jan 2019
19:46:08 -0500:

> Hi Miquèl,
> 
> On Wed, 30 Jan 2019 10:46:06 +0100, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> 
> > > > > Today, there is no S2RAM support for switches. First, I proposed to add
> > > > > suspend/resume callbacks to the mv88e6xxx driver - just enough to avoid
> > > > > crashing the kernel.    
> > > > 
> > > > Then i would suggest the mv88e6xxx refuses the suspend. Actually that
> > > > probably is the first correct step. We don't have suspend support, so
> > > > stop the suspend happening, so preventing the kernel crash.    
> 
> Actually can you show me the crash that is happening?

Sure, here it is: http://code.bulix.org/swwb11-569137

Actually it is a silent crash but the platform never resumes. I am
pretty sure this is due to the kthread_queue_delayed_work() loop which
might access registers before it is allowed to do so. In my proposal I
just canceled it at suspend and restarted it at resume.

Next week I will send a patch to refuse the suspend as you both
suggested and if people want to suspend, they will have to remove the
switch support.


Thanks,
Miquèl