linux-kernel - Re: [PATCH net-next v2 3/7] net: ethernet: fs_enet: drop the .adjust_link custom fs

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Message-ID: <58cf7db3-4321-4bd9-a422-3642ce59f21f@lunn.ch>
Date: Wed, 4 Sep 2024 14:36:58 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, Pantelis Antoniou <pantelis.antoniou@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Russell King <linux@...linux.org.uk>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Florian Fainelli <f.fainelli@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
	Herve Codina <herve.codina@...tlin.com>,
	Simon Horman <horms@...nel.org>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH net-next v2 3/7] net: ethernet: fs_enet: drop the
 .adjust_link custom fs_ops

On Wed, Sep 04, 2024 at 10:27:11AM +0200, Maxime Chevallier wrote:
> Hi Andrew,
> 
> On Fri, 30 Aug 2024 23:06:08 +0200
> Andrew Lunn <andrew@...n.ch> wrote:
> 
> > > --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
> > > +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
> > > @@ -649,12 +649,7 @@ static void fs_adjust_link(struct net_device *dev)
> > >  	unsigned long flags;
> > >  
> > >  	spin_lock_irqsave(&fep->lock, flags);
> > > -
> > > -	if (fep->ops->adjust_link)
> > > -		fep->ops->adjust_link(dev);
> > > -	else
> > > -		generic_adjust_link(dev);
> > > -
> > > +	generic_adjust_link(dev);
> > >  	spin_unlock_irqrestore(&fep->lock, flags);  
> > 
> > Holding a spinlock is pretty unusual. We are in thread context, and
> > the phydev mutex is held. Looking at generic_adjust_link, do any of
> > the fep->foo variables actually need protecting, particularly from
> > changes in interrupts context?
> 
> Yes there are, the interrupt mask/event registers are being accessed
> from the interrupt handler and the ->restart() hook. I can try to
> rework this a bit for a cleaner interrupt handling, but I don't have
> means to test this on all mac flavors (fec/fcc/scc) :(

As far as i can see, none of the fep->old* members are accessed
outside of fs_enet-main.c. There values are not important for the
restart call. So the spinlock has nothing to do with adjust_link as
such, but restart. So maybe narrow down the lock to just the restart
call? But it is not a big issues, just unusual.

	Andrew