linux-kernel - Re: [PATCH 5.10 64/98] net: mdio-mux: Handle -EPROBE

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Date:   Tue, 24 Aug 2021 21:00:09 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Saravana Kannan <saravanak@...gle.com>,
        Andrew Lunn <andrew@...n.ch>, Marc Zyngier <maz@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 5.10 64/98] net: mdio-mux: Handle -EPROBE_DEFER correctly

Hi1

> When registering mdiobus children, if we get an -EPROBE_DEFER, we shouldn't
> ignore it and continue registering the rest of the mdiobus children. This
> would permanently prevent the deferring child mdiobus from working instead
> of reattempting it in the future. So, if a child mdiobus needs to be
> reattempted in the future, defer the entire mdio-mux initialization.
> 
> This fixes the issue where PHYs sitting under the mdio-mux aren't
> initialized correctly if the PHY's interrupt controller is not yet ready
> when the mdio-mux is being probed. Additional context in the link
> below.

I don't believe this is quite right. AFAICT it leaks memory in the
EPROBE_DEFER case. Could someone double-check? Suggested fix is below.

> +++ b/drivers/net/mdio/mdio-mux.c
> @@ -175,11 +175,15 @@ int mdio_mux_init(struct device *dev,
>  		cb->mii_bus->write = mdio_mux_write;
>  		r = of_mdiobus_register(cb->mii_bus, child_bus_node);
>  		if (r) {
> +			mdiobus_free(cb->mii_bus);
> +			if (r == -EPROBE_DEFER) {
> +				ret_val = r;
> +				goto err_loop;
> +			}
> +			devm_kfree(dev, cb);
>  			dev_err(dev,
>  				"Error: Failed to register MDIO bus for child %pOF\n",
>  				child_bus_node);
> -			mdiobus_free(cb->mii_bus);
> -			devm_kfree(dev, cb);
>  		} else {
>  			cb->next = pb->children;
>  			pb->children = cb;


Signed-off-by: Pavel Machek (CIP) <pavel@...x.de>

diff --git a/drivers/net/mdio/mdio-mux.c b/drivers/net/mdio/mdio-mux.c
index ccb3ee704eb1..6d0e505343c5 100644
--- a/drivers/net/mdio/mdio-mux.c
+++ b/drivers/net/mdio/mdio-mux.c
@@ -163,6 +163,7 @@ int mdio_mux_init(struct device *dev,
 		cb->mii_bus = mdiobus_alloc();
 		if (!cb->mii_bus) {
 			ret_val = -ENOMEM;
+			devm_kfree(dev, cb);
 			goto err_loop;
 		}
 		cb->mii_bus->priv = cb;
@@ -176,11 +177,11 @@ int mdio_mux_init(struct device *dev,
 		r = of_mdiobus_register(cb->mii_bus, child_bus_node);
 		if (r) {
 			mdiobus_free(cb->mii_bus);
+			devm_kfree(dev, cb);
 			if (r == -EPROBE_DEFER) {
 				ret_val = r;
 				goto err_loop;
 			}
-			devm_kfree(dev, cb);
 			dev_err(dev,
 				"Error: Failed to register MDIO bus for child %pOF\n",
 				child_bus_node);


-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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