netdev - RE: [PATCH net v2 1/2] net: stmmac: fix PHY handle parsing

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Date:   Tue, 21 Mar 2023 08:34:49 +0000
From:   "Sit, Michael Wei Hong" <michael.wei.hong.sit@...el.com>
To:     Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>
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 v2 1/2] net: stmmac: fix PHY handle parsing



> -----Original Message-----
> From: Russell King <linux@...linux.org.uk>
> Sent: Saturday, March 18, 2023 4:58 AM
> To: Andrew Lunn <andrew@...n.ch>
> Cc: Sit, Michael Wei Hong <michael.wei.hong.sit@...el.com>;
> 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 v2 1/2] net: stmmac: fix PHY handle
> parsing
> 
> On Fri, Mar 17, 2023 at 08:56:19PM +0100, Andrew Lunn wrote:
> > On Tue, Mar 14, 2023 at 03:02:07PM +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.
> >
> > Please could you expand the commit message because i'm
> having trouble
> > following this.
> >
> > phylink_fwnode_phy_connect() says:
> >
> > 	/* Fixed links and 802.3z are handled without needing a
> PHY */
> > 	if (pl->cfg_link_an_mode == MLO_AN_FIXED ||
> > 	    (pl->cfg_link_an_mode == MLO_AN_INBAND &&
> > 	     phy_interface_mode_is_8023z(pl->link_interface)))
> > 		return 0;
> >
> > So your first statement is not true. It should be
> MLO_AN_INBAND and
> > phy_interface_mode_is_8023z.
> >
> > > Add additional check for PHY handle parsing when set to
> MLO_AN_INBAND.
> >
> > Looking at the patch, there is no reference to
> MLO_AN_INBAND, or
> > managed = "in-band-status";
> 
> That's the pesky "xpcs_an_inband" which ends up as phylink's
> "ovr_an_inband"... I'm sure these are random renames of stuff
> to make sure that people struggle to follow the code.
> 
It is as mentioned above, the "xpcs_an_inband" will end up as
"ovr_an_inband" which will then
set pl->cfg_link_an_mode = MLO_AN_INBAND in the
phylink_parse_mode() in phylink.c

The phylink_fwnode_phy_connect() checks if both
MLO_AN_INBAND && phy_interface_mode_is_8023z() true
before returning 0.

But in our case, we only have MLO_AN_INBAND is true, which
then goes to the next part of the code.

	phy_fwnode = fwnode_get_phy_node(fwnode);
	if (IS_ERR(phy_fwnode)) {
		if (pl->cfg_link_an_mode == MLO_AN_PHY)
			return -ENODEV;
		return 0;
	}

Where here the IS_ERR(phy_fwnode) returns true, then it
Checks for MLO_AN_PHY, which in our case is not, so it returns
a 0.

When returned 0, our driver will then skip the manual phy parsing
due to if (!fwnode || ret)
> --
> RMK's Patch system:
> https://www.armlinux.org.uk/developer/patches/
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