netdev - Re: [PATCH v2 2/6] net: phy: broadcom: Add BCM54810 PHY entry

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Date:   Tue, 1 Nov 2016 11:59:53 -0400
From:   Jon Mason <jon.mason@...adcom.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com, rafal@...ecki.pl,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/6] net: phy: broadcom: Add BCM54810 PHY entry

On Sat, Oct 29, 2016 at 10:18:39AM +0200, Andrew Lunn wrote:
> On Fri, Oct 28, 2016 at 04:56:55PM -0400, Jon Mason wrote:
> > The BCM54810 PHY requires some semi-unique configuration, which results
> > in some additional configuration in addition to the standard config.
> > Also, some users of the BCM54810 require the PHY lanes to be swapped.
> > Since there is no way to detect this, add a device tree query to see if
> > it is applicable.
> > 
> > Inspired-by: Vikas Soni <vsoni@...adcom.com>
> > Signed-off-by: Jon Mason <jon.mason@...adcom.com>
> > ---
> >  drivers/net/phy/Kconfig    |  2 +-
> >  drivers/net/phy/broadcom.c | 58 +++++++++++++++++++++++++++++++++++++++++++++-
> >  include/linux/brcmphy.h    | 10 ++++++++
> 
> Hi Jon
> 
> The binding documentation is missing.
> 
> > +	if (of_property_read_bool(np, "brcm,enet-phy-lane-swap")) {
> > +		/* Lane Swap - Undocumented register...magic! */
> > +		ret = bcm_phy_write_exp(phydev, MII_BCM54XX_EXP_SEL_ER + 0x9,
> > +					0x11B);
> > +		if (ret < 0)
> > +			return ret;
> > +	}
> > +
> 
> I wounder if this property could be made generic? What exactly are you
> swapping? Rx and Tx lanes? Maybe we should add it to phy.txt?

Are you envisioning adding a DT check (similar to the
of_property_read_bool above, only with a more generic string) in
phy_device_create(), which will then set a PHY device flag?  This flag
would then be checked for in the PHY driver and the appropriate action
taken (in this case the bcm_phy_write_exp above).

If so, I cam completely fine doing this.  I think the only caveat
would be that this would be creating a generic interface for only 1
user.  If you envision this being used by others, then disregard my
concern.

Thanks,
Jon

> 
> 	  Andrew