linux-kernel - Re: [PATCH net] net: dsa: mxl-gsw1xx: manually clear RANEG bit

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Message-ID: <aTL886vReHP74XPn@makrotopia.org>
Date: Fri, 5 Dec 2025 15:40:35 +0000
From: Daniel Golle <daniel@...rotopia.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Andrew Lunn <andrew@...n.ch>, Hauke Mehrtens <hauke@...ke-m.de>,
	Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Rasmus Villemoes <ravi@...vas.dk>,
	"Benny (Ying-Tsan) Weng" <yweng@...linear.com>,
	John Crispin <john@...ozen.org>
Subject: Re: [PATCH net] net: dsa: mxl-gsw1xx: manually clear RANEG bit

On Fri, Dec 05, 2025 at 03:17:37PM +0000, Russell King (Oracle) wrote:
> On Fri, Dec 05, 2025 at 01:56:39PM +0000, Daniel Golle wrote:
> > On Fri, Dec 05, 2025 at 02:45:35PM +0100, Andrew Lunn wrote:
> > > On Fri, Dec 05, 2025 at 01:32:20AM +0000, Daniel Golle wrote:
> > > > Despite being documented as self-clearing, the RANEG bit sometimes
> > > > remains set, preventing auto-negotiation from happening.
> > > > 
> > > > Manually clear the RANEG bit after 10ms as advised by MaxLinear, using
> > > > delayed_work emulating the asynchronous self-clearing behavior.
> > > 
> > > Maybe add some text why the complexity of delayed work is used, rather
> > > than just a msleep(10)?
> > > 
> > > Calling regmap_read_poll_timeout() to see if it clears itself could
> > > optimise this, and still be simpler.
> > 
> > Is the restart_an() operation allowed to sleep? Looking at other
> > drivers I only ever see that it sets a self-clearing AN RESTART bit,
> > never waiting for that bit to clear. Hence I wanted to immitate
> > that behavior by clearing the bit asynchronously. If that's not needed
> > and msleep(10) or usleep_range(10000, 20000) can be used instead that'd
> > be much easier, of course.
> 
> Sleeping is permitted in this code path, but bear in mind that it
> will be called from ethtool ops, and thus the RTNL will be held,
> please keep sleep durations to a minimum.

In that sense 10ms (on top of the MDIO operation) is not that little.
Maybe it is worth to use delayed_work to clear the bit after all...