linux-kernel - RE: [PATCH net 1/2] net: stmmac: fix PHY handle parsing

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Date:   Tue, 14 Mar 2023 08:47:24 +0000
From:   "Sit, Michael Wei Hong" <michael.wei.hong.sit@...el.com>
To:     "Raczynski, Piotr" <piotr.raczynski@...el.com>
CC:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        "Jakub Kicinski" <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "Ong, Boon Leong" <boon.leong.ong@...el.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Looi, Hong Aun" <hong.aun.looi@...el.com>,
        "Voon, Weifeng" <weifeng.voon@...el.com>,
        "Lai, Peter Jun Ann" <peter.jun.ann.lai@...el.com>
Subject: RE: [PATCH net 1/2] net: stmmac: fix PHY handle parsing



> -----Original Message-----
> From: Raczynski, Piotr <piotr.raczynski@...el.com>
> Sent: Tuesday, March 14, 2023 4:39 PM
> To: Sit, Michael Wei Hong <michael.wei.hong.sit@...el.com>
> Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>; Alexandre
> Torgue <alexandre.torgue@...s.st.com>; Jose Abreu
> <joabreu@...opsys.com>; David S . Miller <davem@...emloft.net>;
> Eric Dumazet <edumazet@...gle.com>; Jakub Kicinski
> <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Maxime
> Coquelin <mcoquelin.stm32@...il.com>; Ong, Boon Leong
> <boon.leong.ong@...el.com>; netdev@...r.kernel.org; linux-
> stm32@...md-mailman.stormreply.com; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; Looi,
> Hong Aun <hong.aun.looi@...el.com>; Voon, Weifeng
> <weifeng.voon@...el.com>; Lai, Peter Jun Ann
> <peter.jun.ann.lai@...el.com>
> Subject: Re: [PATCH net 1/2] net: stmmac: fix PHY handle parsing
> 
> On Mon, Mar 13, 2023 at 04:01:34PM +0800, Michael Sit Wei Hong
> wrote:
> > phylink_fwnode_phy_connect returns 0 when set to
> MLO_AN_INBAND.
> > This causes the PHY handle parsing to skip and the PHY will not be
> > attached to the MAC.
> >
> > Add additional check for PHY handle parsing when set to
> MLO_AN_INBAND.
> >
> > Fixes: ab21cf920928 ("net: stmmac: make mdio register skips PHY
> > scanning for fixed-link")
> > Signed-off-by: Michael Sit Wei Hong
> <michael.wei.hong.sit@...el.com>
> > Signed-off-by: Lai Peter Jun Ann <peter.jun.ann.lai@...el.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8
> ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 8f543c3ab5c5..398adcd68ee8 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -1134,6 +1134,7 @@ static void
> stmmac_check_pcs_mode(struct
> > stmmac_priv *priv)  static int stmmac_init_phy(struct net_device
> *dev)
> > {
> >  	struct stmmac_priv *priv = netdev_priv(dev);
> > +	struct fwnode_handle *fixed_node;
> >  	struct fwnode_handle *fwnode;
> >  	int ret;
> >
> > @@ -1141,13 +1142,16 @@ static int stmmac_init_phy(struct
> net_device *dev)
> >  	if (!fwnode)
> >  		fwnode = dev_fwnode(priv->device);
> >
> > -	if (fwnode)
> > +	if (fwnode) {
> > +		fixed_node =
> fwnode_get_named_child_node(fwnode, "fixed-link");
> > +		fwnode_handle_put(fixed_node);
> >  		ret = phylink_fwnode_phy_connect(priv->phylink,
> fwnode, 0);
> > +	}
> >
> 
> On the occasion, why not rewrite above to:
> if (!fwnode)
> ...
> else
> ...
> 
> or:
> if(fwnode)
> ...
> else
> ?
> 
The (!fwnode) serves as a NULL check, and if the fwnode is NULL, we try to populate it using dev_fwnode.
If fwnode is then populated, then the if(fwnode) code will run.

If fwnode is still NULL after dev_fwnode, fwnode_get_named_child_node will generate a kernel panic if no
NULL check is present.
> >  	/* Some DT bindings do not set-up the PHY handle. Let's try
> to
> >  	 * manually parse it
> >  	 */
> > -	if (!fwnode || ret) {
> > +	if (!fwnode || ret || !fixed_node) {
> >  		int addr = priv->plat->phy_addr;
> >  		struct phy_device *phydev;
> >
> > --
> > 2.34.1
> >