of_mdio: add new DT property 'managed' to specify the PHY management type

[ Upstream commit 4cba5c2103657d43d0886e4cff8004d95a3d0def in net-next tree,
  will be pushed to Linus very soon. ]

Currently the PHY management type is selected by the MAC driver arbitrary.
The decision is based on the presence of the "fixed-link" node and on a
will of the driver's authors.
This caused a regression recently, when mvneta driver suddenly started
to use the in-band status for auto-negotiation on fixed links.
It appears the auto-negotiation may not work when expected by the MAC driver.
Sebastien Rannou explains:
<< Yes, I confirm that my HW does not generate an in-band status. AFAIK, it's
a PHY that aggregates 4xSGMIIs to 1xQSGMII ; the MAC side of the PHY (with
inband status) is connected to the switch through QSGMII, and in this context
we are on the media side of the PHY. >>
https://lkml.org/lkml/2015/7/10/206

This patch introduces the new string property 'managed' that allows
the user to set the management type explicitly.
The supported values are:
"auto" - default. Uses either MDIO or nothing, depending on the presence
of the fixed-link node
"in-band-status" - use in-band status

Signed-off-by: Stas Sergeev <stsp@users.sourceforge.net>

CC: Rob Herring <robh+dt@kernel.org>
CC: Pawel Moll <pawel.moll@arm.com>
CC: Mark Rutland <mark.rutland@arm.com>
CC: Ian Campbell <ijc+devicetree@hellion.org.uk>
CC: Kumar Gala <galak@codeaurora.org>
CC: Florian Fainelli <f.fainelli@gmail.com>
CC: Grant Likely <grant.likely@linaro.org>
CC: devicetree@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 0c064485d1c2..bec8ec2b31f6 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -263,7 +263,8 @@ EXPORT_SYMBOL(of_phy_attach);
 bool of_phy_is_fixed_link(struct device_node *np)
 {
 	struct device_node *dn;
-	int len;
+	int len, err;
+	const char *managed;
 
 	/* New binding */
 	dn = of_get_child_by_name(np, "fixed-link");
@@ -272,6 +273,10 @@ bool of_phy_is_fixed_link(struct device_node *np)
 		return true;
 	}
 
+	err = of_property_read_string(np, "managed", &managed);
+	if (err == 0 && strcmp(managed, "auto") != 0)
+		return true;
+
 	/* Old binding */
 	if (of_get_property(np, "fixed-link", &len) &&
 	    len == (5 * sizeof(__be32)))
@@ -286,8 +291,18 @@ int of_phy_register_fixed_link(struct device_node *np)
 	struct fixed_phy_status status = {};
 	struct device_node *fixed_link_node;
 	const __be32 *fixed_link_prop;
-	int len;
+	int len, err;
 	struct phy_device *phy;
+	const char *managed;
+
+	err = of_property_read_string(np, "managed", &managed);
+	if (err == 0) {
+		if (strcmp(managed, "in-band-status") == 0) {
+			/* status is zeroed, namely its .link member */
+			phy = fixed_phy_register(PHY_POLL, &status, np);
+			return IS_ERR(phy) ? PTR_ERR(phy) : 0;
+		}
+	}
 
 	/* New binding */
 	fixed_link_node = of_get_child_by_name(np, "fixed-link");