linux-kernel - RE: [BUG] net: phy: genphy_loopback: add link speed configuration

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Date:   Wed, 15 Dec 2021 15:03:52 +0000
From:   "Ismail, Mohammad Athari" <mohammad.athari.ismail@...el.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Oleksij Rempel <o.rempel@...gutronix.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Voon, Weifeng" <weifeng.voon@...el.com>,
        "Wong, Vee Khee" <vee.khee.wong@...el.com>
Subject: RE: [BUG] net: phy: genphy_loopback: add link speed configuration



> -----Original Message-----
> From: Andrew Lunn <andrew@...n.ch>
> Sent: Wednesday, December 15, 2021 5:55 PM
> To: Ismail, Mohammad Athari <mohammad.athari.ismail@...el.com>
> Cc: Oleksij Rempel <o.rempel@...gutronix.de>; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org; Voon, Weifeng <weifeng.voon@...el.com>;
> Wong, Vee Khee <vee.khee.wong@...el.com>
> Subject: Re: [BUG] net: phy: genphy_loopback: add link speed configuration
> 
> > > -----Original Message-----
> > > From: Andrew Lunn <andrew@...n.ch>
> > > Sent: Wednesday, December 15, 2021 5:23 PM
> > > To: Ismail, Mohammad Athari <mohammad.athari.ismail@...el.com>
> > > Cc: Oleksij Rempel <o.rempel@...gutronix.de>;
> > > netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Voon, Weifeng
> > > <weifeng.voon@...el.com>; Wong, Vee Khee
> <vee.khee.wong@...el.com>
> > > Subject: Re: [BUG] net: phy: genphy_loopback: add link speed
> > > configuration
> > >
> > > > Thanks for the suggestion. The proposed solution also doesn't
> > > > work. Still
> > > get -110 error.
> > >
> > > Please can you trace where this -110 comes from. Am i looking at the
> > > wrong poll call?
> >
> > I did read the ret value from genphy_soft_reset() and
> phy_read_poll_timeout().
> > The -110 came from phy_read_poll_timeout().
> 
> O.K.
> 
> Does the PHY actually do loopback, despite the -110?

As Intel Elkhart Lake is using stmmac driver, in stmmac_selftest, return value of phy_loopback() is checked as well. If it return -110, the selftest that using PHY loopback will be recorded as -110 (fail).

> 
> I'm wondering if we should ignore the return value from
> phy_read_poll_timeout().

Removing/ignoring the return value from phy_read_poll_timeout() can work. But, the -110 error message will be displayed in dmesg. It is because there is phydev_err() as part of phy_read_poll_timeout() definition.

-Athari-

> 
> 	Andrew