linux-kernel - Re: [PATCH net-next 5/9] net: dsa: vsc73xx: use mutex to mdio operations

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Message-ID: <bf450358-1286-453e-9601-17bb2077ee88@lunn.ch>
Date: Tue, 30 Jul 2024 01:07:17 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Pawel Dembicki <paweldembicki@...il.com>
Cc: netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>,
	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>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 5/9] net: dsa: vsc73xx: use mutex to mdio
 operations

On Mon, Jul 29, 2024 at 11:06:11PM +0200, Pawel Dembicki wrote:
> vsc73xx needs mutex during mdio bus access to avoid races. Without it,
> phys are misconfigured and bus operations aren't work as expected.

This is adding much more than a mutex.

The mdio core already has a mutex, so there should not be multiple
parallel operations going on. So i don't think the mutex itself is the
fix. It is more likely to be a change in the timing. Which in itself
is not good. Maybe use your new vsc73xx_mdio_busy_check() with one of
the helpers in include/linux/iopoll.h

    Andrew

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