linux-kernel - Re: [PATCH net 2/2] net: phy: Check harder for errors in get_phy

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Message-ID: <20200619133040.GO1551@shell.armlinux.org.uk>
Date:   Fri, 19 Jun 2020 14:30:40 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Dajun Jin <adajunjin@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH net 2/2] net: phy: Check harder for errors in get_phy_id()

On Fri, Jun 19, 2020 at 03:26:59PM +0200, Andrew Lunn wrote:
> On Thu, Jun 18, 2020 at 09:47:59PM -0700, Florian Fainelli wrote:
> > Commit 02a6efcab675 ("net: phy: allow scanning busses with missing
> > phys") added a special condition to return -ENODEV in case -ENODEV or
> > -EIO was returned from the first read of the MII_PHYSID1 register.
> > 
> > In case the MDIO bus data line pull-up is not strong enough, the MDIO
> > bus controller will not flag this as a read error. This can happen when
> > a pluggable daughter card is not connected and weak internal pull-ups
> > are used (since that is the only option, otherwise the pins are
> > floating).
> > 
> > The second read of MII_PHYSID2 will be correctly flagged an error
> > though, but now we will return -EIO which will be treated as a hard
> > error, thus preventing MDIO bus scanning loops to continue succesfully.
> > 
> > Apply the same logic to both register reads, thus allowing the scanning
> > logic to proceed.
> 
> Hi Florian
> 
> Maybe extend the kerneldoc for this function to document the return
> values and there special meanings?

You mean like the patch I sent yesterday?

> BTW: Did you look at get_phy_c45_ids()? Is it using the correct return
> value? Given the current work being done to extend scanning to C45,
> maybe it needs reviewing for issues like this.

And the updates I sent for this yesterday? ;)

-- 
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