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Date:   Thu, 16 Jun 2022 17:30:57 +0200
From:   Oleksij Rempel <o.rempel@pengutronix.de>
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, kernel@pengutronix.de,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH net-next v1 1/1] net: dsa: ar9331: fix potential dead
 lock on mdio access
Message-ID: <20220616153057.GB28995@pengutronix.de>
References: <20220616112550.877118-1-o.rempel@pengutronix.de>
 <YqsxWv79Ge1AFiQx@lunn.ch>
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On Thu, Jun 16, 2022 at 03:34:18PM +0200, Andrew Lunn wrote:
> >  static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len,
> > @@ -849,6 +849,8 @@ static int ar9331_mdio_read(void *ctx, const void *reg_buf, size_t reg_len,
> >  		return 0;
> >  	}
> >  
> > +	mutex_lock_nested(&sbus->mdio_lock, MDIO_MUTEX_NESTED);
> > +
> 
> Do you know about mdiobus_read_nested() and
> mdiobus_write_nested(). The mv88e6xxx driver uses these.

Yes.

I need at least 2 master MDIO accesses to implement 1 slave mdio access.
So I decided to get lock one time for all needed accesses instead of
taking it multiple times.

Regards,
Oleksij
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