From: "Russell King (Oracle)" <linux@armlinux•org.uk>
To: Biju Das <biju.das.jz@bp•renesas.com>
Cc: Andrew Lunn <andrew@lunn•ch>,
"biju.das.au" <biju.das.au@gmail•com>,
Heiner Kallweit <hkallweit1@gmail•com>,
"David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Jakub Kicinski <kuba@kernel•org>, Paolo Abeni <pabeni@redhat•com>,
Ovidiu Panait <ovidiu.panait.rb@renesas•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>,
Geert Uytterhoeven <geert+renesas@glider•be>,
Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp•renesas.com>,
"linux-renesas-soc@vger•kernel.org"
<linux-renesas-soc@vger•kernel.org>
Subject: Re: [PATCH net-next] net: phy: call phy_init_hw() in phy resume path
Date: Sat, 11 Apr 2026 00:49:14 +0100 [thread overview]
Message-ID: <admMethCSjOQhu8g@shell.armlinux.org.uk> (raw)
In-Reply-To: <TY3PR01MB11346B6680E5952BD7B7078CA86592@TY3PR01MB11346.jpnprd01.prod.outlook.com>
On Fri, Apr 10, 2026 at 04:41:08PM +0000, Biju Das wrote:
> Hi Andrew,
>
> > -----Original Message-----
> > From: Andrew Lunn <andrew@lunn•ch>
> > Sent: 10 April 2026 16:15
> > Subject: Re: [PATCH net-next] net: phy: call phy_init_hw() in phy resume path
> >
> > > Apart from that, looks fine to me - it seems some paths call
> > > phy_init_hw() can be called with or without phydev->lock held, and
> > > this one will call it with the lock held which seems to be okay.
> >
> > Haven't we had deadlocks in this area before?
> >
> > Please test with CONFIG_PROVE_LOCKING enabled.
>
> I have n't faced any issue with micrel phy. But my collegue
> got the below issue with Microsemi phy. It doesn't finish the boot.
>
> drivers/net/phy/mscc/mscc_main.c
Looking at this driver, I'm wondering why it's taking phydev->lock
in vsc85xx_edge_rate_cntl_set()... phy_modify_paged() is already
a fully locked atomic operation (it takes the bus lock) and taking
phydev->lock gains nothing.
vsc85xx_mac_if_set() is a different matter, and this _should_ be
using phy_modify() to atomically change MSCC_PHY_EXT_PHY_CNTL_1.
phydev->lock doesn't guarantee that e.g. userspace won't access
the register behind this code's back.
vsc8531_pre_init_seq_set() is a repeat of vsc85xx_edge_rate_cntl_set()
except with phy_select_page()..phy_restore_page() which does the
necessary bus locking to ensure the entire sequence is done atomically.
Ditto vsc85xx_eee_init_seq_set().
So, I question whether any of the functions in this driver actually
have a valid reason to take phydev->lock - looks to me like a not
very well written driver.
In cases like this, I don't think we should make things more
difficult in the core just because we have a lockdep splat when that
can be avoided by killing off unnecessary locking.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2026-04-10 23:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-10 14:29 [PATCH net-next] net: phy: call phy_init_hw() in phy resume path Biju
2026-04-10 14:51 ` Russell King (Oracle)
2026-04-10 14:55 ` Russell King (Oracle)
2026-04-10 17:27 ` Biju Das
2026-04-10 23:51 ` Russell King (Oracle)
2026-04-10 15:15 ` Andrew Lunn
2026-04-10 15:22 ` Russell King (Oracle)
2026-04-10 15:38 ` Biju Das
2026-04-10 16:00 ` Andrew Lunn
2026-04-10 16:41 ` Biju Das
2026-04-10 23:49 ` Russell King (Oracle) [this message]
2026-04-11 13:50 ` Andrew Lunn
2026-04-11 14:32 ` Biju Das
2026-04-11 16:46 ` Russell King (Oracle)
2026-04-12 12:05 ` Biju Das
2026-04-12 12:55 ` Russell King (Oracle)
2026-04-10 17:00 ` Florian Fainelli
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