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

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Date:   Tue, 1 Nov 2016 17:26:48 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Jon Mason <jon.mason@...adcom.com>
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

> > > +	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.

	Andrew