linux-kernel - Re: [PATCH 1/3] net: thunderx: Cleanup PHY probing code.

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Message-ID: <56E31E7A.6080905@gmail.com>
Date:	Fri, 11 Mar 2016 11:37:30 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Andrew Lunn <andrew@...n.ch>,
	David Daney <ddaney@...iumnetworks.com>
Cc:	David Daney <ddaney.cavm@...il.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Robert Richter <rric@...nel.org>,
	Sunil Goutham <sgoutham@...ium.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Radha Mohan Chintakuntla <rchintakuntla@...ium.com>,
	linux-kernel@...r.kernel.org, David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 1/3] net: thunderx: Cleanup PHY probing code.

On 11/03/16 11:06, Andrew Lunn wrote:
>>> I don't see why it should wait around forever. I have boards with
>>> Marvell PHYs, yet if i don't build the Marvell driver, the Ethernet
>>> driver still loads, because the generic PHY driver is used instead.
>>> Why does this not work here?
>>
>> As I said before, there is no driver for the device, so
>> of_phy_find_device() will always return NULL.
> 
> I'm not yet convinced this is true. I really do expect that the
> generic PHY driver will bind to it. It might then go horribly wrong,
> because it is not standard compliant, but that is a different issue.

I concur with Andrew here, unless the PHY is guaranteed to return
garbage when get_phy_id() is called, there is a good chance that the
Generic PHY driver will be bound to this PHY device, or this is not
happening for you for some reason?

> 
> The generic driver should probably have a black list for such devices.
> This is a PHY issue, not an MDIO issue, and the problem should be
> solved in the PHY layer, not in one MDIO driver.

I considered the possibility once of disabling the generic PHY driver,
such that systems where the vendor-specific PHY driver is expected to be
used could utilize that. That does not play well with the fixed PHYs
using the generic PHY driver though, anyway, I am digressing.

> 
> We should also consider what happens when somebody actually writes a
> driver for this PHY. Are you not going to use it?
> 
> Before this patchset, you did not special case this compatible
> string. So at the very least, you need to split this into a separate
> patch, so the maintainers can ACK/NACK it, independent of the other
> change it is embedded in.
> 
>        Andrew
> 


-- 
Florian