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

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Message-ID: <20161101164337.GA19654@broadcom.com>
Date:   Tue, 1 Nov 2016 12:43:39 -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 Tue, Nov 01, 2016 at 05:26:48PM +0100, Andrew Lunn wrote:
> > > > +	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).
> 
> I would keep the parsing of the property in the driver. But if we
> think other PHYs could also support this feature, it would be good to
> avoid having "brcm,enet-phy-lane-swap", "marvell,enet-phy-lane-swap",
> "davicom,enet-phy-lane-swap", etc. It would be better to have one well
> defined property documented in phy.txt which any PHY is free to
> implement.

Okay, I understand what you are saying now.  I will assume that if
nothing exists today aside from this Broadcom errata, something in the
future will happen.  So, I agree that making it generic is a good idea.

I'll make the generic string be "enet-phy-lane-swap" (without the
previous "brcm"), and add the flag to phy.txt to document it.

Thanks,
Jon

> 
> 	Andrew