[PATCH 1/2] of_mdio: add new DT property 'link' for fixed-link

[Stas Sergeev <stsp@list.ru>]

Currently for fixed-link the link state is always set to UP.
This patch introduces the new property 'link' that accepts the
following string arguments: "up", "down" and "auto".
"down" may be needed if the link is physically unconnected.
"auto" is needed to enable the link paramaters auto-negotiation,
that is built into some MII protocols, namely SGMII.
The appropriate documentation is added and explicitly states that
"auto" is very specific (protocol, HW and driver-specific), and
is therefore should be used with care.

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
---
 .../devicetree/bindings/net/fixed-link.txt         |  8 +++-
 drivers/of/of_mdio.c                               | 48 ++++++++++++++++++++--
 include/linux/of_mdio.h                            |  5 +++
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/fixed-link.txt b/Documentation/devicetree/bindings/net/fixed-link.txt
index 82bf7e0..070f554 100644
--- a/Documentation/devicetree/bindings/net/fixed-link.txt
+++ b/Documentation/devicetree/bindings/net/fixed-link.txt
@@ -9,8 +9,14 @@ Such a fixed link situation is described by creating a 'fixed-link'
 sub-node of the Ethernet MAC device node, with the following
 properties:

+* 'link' (string, optional), to indicate the link state. Accepted
+  values are "up", "down" and "auto". "auto" means auto-negotiation of
+  link parameters. Auto-negotiation is MII protocol, HW and driver-specific
+  and is not supported in many cases, so use it only when you know what
+  you do.
 * 'speed' (integer, mandatory), to indicate the link speed. Accepted
-  values are 10, 100 and 1000
+  values are 10, 100 and 1000. If the 'link' property is set to 'auto',
+  'speed' may not be set. It will then be auto-negotiated, if possible.
 * 'full-duplex' (boolean, optional), to indicate that full duplex is
   used. When absent, half duplex is assumed.
 * 'pause' (boolean, optional), to indicate that pause should be
diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index 1bd4305..2152cf8 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -280,6 +280,26 @@ bool of_phy_is_fixed_link(struct device_node *np)
 }
 EXPORT_SYMBOL(of_phy_is_fixed_link);

+bool of_phy_is_autoneg_link(struct device_node *np)
+{
+	struct device_node *dn;
+	const char *link_str;
+	int rc;
+	bool ret = false;
+
+	dn = of_get_child_by_name(np, "fixed-link");
+	if (!dn)
+		return false;
+
+	rc = of_property_read_string(dn, "link", &link_str);
+	if (rc == 0 && strcmp(link_str, "auto") == 0)
+		ret = true;
+
+	of_node_put(dn);
+	return ret;
+}
+EXPORT_SYMBOL(of_phy_is_autoneg_link);
+
 int of_phy_register_fixed_link(struct device_node *np)
 {
 	struct fixed_phy_status status = {};
@@ -291,11 +311,33 @@ int of_phy_register_fixed_link(struct device_node *np)
 	/* New binding */
 	fixed_link_node = of_get_child_by_name(np, "fixed-link");
 	if (fixed_link_node) {
-		status.link = 1;
+		const char *link_str;
+		int ret;
+		bool link_auto = false;
+
+		ret = of_property_read_string(fixed_link_node, "link",
+					      &link_str);
+		if (ret == 0) {
+			if (strcmp(link_str, "up") == 0)
+				status.link = 1;
+			else
+				status.link = 0;
+			if (strcmp(link_str, "auto") == 0)
+				link_auto = true;
+		} else {
+			status.link = 1;
+		}
 		status.duplex = of_property_read_bool(fixed_link_node,
 						      "full-duplex");
-		if (of_property_read_u32(fixed_link_node, "speed", &status.speed))
-			return -EINVAL;
+		if (of_property_read_u32(fixed_link_node, "speed",
+					 &status.speed) != 0) {
+			/* in auto mode just set to some sane value:
+			 * it will be changed by MAC later */
+			if (link_auto)
+				status.speed = 1000;
+			else
+				return -EINVAL;
+		}
 		status.pause = of_property_read_bool(fixed_link_node, "pause");
 		status.asym_pause = of_property_read_bool(fixed_link_node,
 							  "asym-pause");
diff --git a/include/linux/of_mdio.h b/include/linux/of_mdio.h
index d449018..647f348 100644
--- a/include/linux/of_mdio.h
+++ b/include/linux/of_mdio.h
@@ -65,6 +65,7 @@ static inline struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np)
 #if defined(CONFIG_OF) && defined(CONFIG_FIXED_PHY)
 extern int of_phy_register_fixed_link(struct device_node *np);
 extern bool of_phy_is_fixed_link(struct device_node *np);
+extern bool of_phy_is_autoneg_link(struct device_node *np);
 #else
 static inline int of_phy_register_fixed_link(struct device_node *np)
 {
@@ -74,6 +75,10 @@ static inline bool of_phy_is_fixed_link(struct device_node *np)
 {
 	return false;
 }
+static inline bool of_phy_is_autoneg_link(struct device_node *np)
+{
+	return false;
+}
 #endif


-- 
1.9.1