linux-kernel - Re: [PATCH net-next v3] net: dsa: mv88e6xxx: Prevent suspend to RAM

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Message-ID: <20190409121454.GB28742@lunn.ch>
Date:   Tue, 9 Apr 2019 14:14:54 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Pavel Machek <pavel@....cz>,
        Vivien Didelot <vivien.didelot@...il.com>,
        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 v3] net: dsa: mv88e6xxx: Prevent suspend to RAM

On Tue, Apr 09, 2019 at 09:06:43AM +0200, Miquel Raynal wrote:
> Hi Pavel,
> 
> Pavel Machek <pavel@....cz> wrote on Mon, 8 Apr 2019 23:55:41 +0200:
> 
> > On Tue 2019-02-05 12:07:28, Miquel Raynal wrote:
> > > On one hand, the mv88e6xxx driver has a work queue called in loop
> > > which will attempt register accesses after MDIO bus suspension, that
> > > entirely freezes the platform during suspend.
> > > 
> > > On the other hand, the DSA core is not ready yet to support suspend to
> > > RAM operation because so far there is no way to recover reliably the
> > > switch configuration.
> > > 
> > > To avoid the kernel to freeze when suspending with a switch driven by
> > > the mv88e6xxx driver, we choose to prevent the driver suspension and
> > > in the same way, the whole platform.
> > > 
> > > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>  
> > 
> > Could we at least do printk() so that user knows what went wrong?
> > 
> > Debugging s2ram is usually not easy :-(.
> 
> I suppose you will be told that suspend was refused by a driver
> (probably without stating which one though). You may send a patch to add
> a trace if you think it is important, as this change as already been
> merged.

Hi Miquel, Pavel

I don't know the s2ram code at all, but this seems like a generic
problem. The core should be reporting which driver returned an error,
not the driver itself.

    Andrew