linux-kernel - Re: [PATCH 05/12] net: phy: add phy_id

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Date:   Wed, 5 Apr 2023 17:27:06 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Richard Cochran <richardcochran@...il.com>,
        Radu Pirea <radu-nicolae.pirea@....nxp.com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Iyappan Subramanian <iyappan@...amperecomputing.com>,
        Keyur Chudgar <keyur@...amperecomputing.com>,
        Quan Nguyen <quan@...amperecomputing.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        devicetree@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH 05/12] net: phy: add phy_id_broken support

On 23-04-05, Florian Fainelli wrote:
> On 4/5/2023 5:27 AM, Andrew Lunn wrote:
> > On Wed, Apr 05, 2023 at 11:26:56AM +0200, Marco Felsch wrote:
> > > Some phy's don't report the correct phy-id, e.g. the TJA1102 dual-port
> > > report 0 for the 2nd port. To fix this a driver needs to supply the
> > > phyid instead and tell the phy framework to not try to readout the
> > > phyid. The latter case is done via the new 'phy_id_broken' flag which
> > > tells the phy framework to skip phyid readout for the corresponding phy.
> > 
> > In general, we try to avoid work around for broken hardware in the
> > core. Please try to solve this within nxp-tja11xx.c.
> 
> Agreed, and one way to solve working around broken PHY identification
> registers is to provide them through the compatible string via
> "ethernet-phyAAAA.BBBB". This forces the PHY library not to read from those
> registers yet instantiate the PHY device and force it to bind to a certain
> phy_driver.

The nxp-tja11xx.c is a bit special in case of two-port devices since the
2nd port registers a 2nd phy device which is correct but don't have a
dedicated compatible and so on. My 2nd idea here was to check if phy_id
is !0 and in this case just use it. I went this way to make it a bit
more explicit.

Regards,
  Marco


> -- 
> Florian
>