[PATCH 2/3] of_mdio: add new DT property 'managed' to specify the PHY management type

[Stas Sergeev <stsp@list.ru>]

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
"mdio" - use MDIO
"in-band-status" - use in-band status
"none" - use fixed-link description

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
---
 Documentation/devicetree/bindings/net/ethernet.txt |  5 ++++
 drivers/of/of_mdio.c                               | 28 ++++++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/ethernet.txt b/Documentation/devicetree/bindings/net/ethernet.txt
index 3fc3605..23743e9 100644
--- a/Documentation/devicetree/bindings/net/ethernet.txt
+++ b/Documentation/devicetree/bindings/net/ethernet.txt
@@ -19,7 +19,12 @@ The following properties are common to the Ethernet controllers:
 - phy: the same as "phy-handle" property, not recommended for new bindings.
 - phy-device: the same as "phy-handle" property, not recommended for new
   bindings.
+- managed: string, specifies the PHY management type. Supported values are:
+  "auto", "mdio", "in-band-status", "none". "auto" is the default, and it
+  sets the management type to either "mdio" or "none", depending on the
+  presence of the "fixed-link" child node.

 Child nodes of the Ethernet controller are typically the individual PHY devices
 connected via the MDIO bus (sometimes the MDIO bus controller is separate).
 They are described in the phy.txt file in this same directory.
+For non-MDIO PHY management see fixed-link.txt.
diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 1bd4305..a460812 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -262,7 +262,16 @@ EXPORT_SYMBOL(of_phy_attach);
 bool of_phy_is_fixed_link(struct device_node *np)
 {
 	struct device_node *dn;
-	int len;
+	int len, m_err;
+	const char *managed;
+
+	m_err = of_property_read_string(np, "managed", &managed);
+	if (m_err == 0) {
+		if (strcmp(managed, "none") == 0)
+			return true;
+		if (strcmp(managed, "mdio") == 0)
+			return false;
+	}

 	/* New binding */
 	dn = of_get_child_by_name(np, "fixed-link");
@@ -271,6 +280,9 @@ bool of_phy_is_fixed_link(struct device_node *np)
 		return true;
 	}

+	if (m_err == 0 && strcmp(managed, "auto") != 0)
+		return true;
+
 	/* Old binding */
 	if (of_get_property(np, "fixed-link", &len) &&
 	    len == (5 * sizeof(__be32)))
@@ -285,8 +297,20 @@ 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, "mdio") == 0)
+			return -EINVAL;
+		if (strcmp(managed, "in-band-status") == 0) {
+			status.link = 0;
+			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");
-- 
1.9.1