[PATCH] net: phy: Add sysfs attribute to prevent PHY suspend

[Sebastian Hesselbarth]

commit 1211ce53077164e0d34641d0ca5fb4d4a7574498
  ("net: phy: resume/suspend PHYs on attach/detach")
introduced a feature to suspend PHYs when entering halted state.

Unfortunately, not all bootloaders properly power-up PHYs on reset
and fail to access ethernet because the PHY is still powered down.

Therefore, this adds code and documentation for a sysfs attribute to
allow/deny PHYs to be suspended on a per-PHY basis. Disabling that
attribute prevents PHYs from being suspended when entering halted state.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth at gmail.com>
Reported-by: Andrew Lunn <andrew at lunn.ch>
---
David,

I know I am late, but I still consider this as a fix for v3.14, therefore
this is based on v3.14-rc1. If you are already done with taking fixes for
v3.14, I can, of course, rebase this upon net-next.

Cc: David Miller <davem at davemloft.net>
Cc: Rob Landley <rob at landley.net>
Cc: Andrew Lunn <andrew at lunn.ch>
Cc: Florian Fainelli <f.fainelli at gmail.com>
Cc: netdev at vger.kernel.org
Cc: linux-doc at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
---
 Documentation/ABI/testing/sysfs-bus-mdio | 10 ++++++++++
 drivers/net/phy/mdio_bus.c               | 26 ++++++++++++++++++++++++++
 drivers/net/phy/phy_device.c             |  5 +++++
 include/linux/phy.h                      |  2 ++
 4 files changed, 43 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-mdio b/Documentation/ABI/testing/sysfs-bus-mdio
index 6349749ebc29..e85a3d350cb1 100644
--- a/Documentation/ABI/testing/sysfs-bus-mdio
+++ b/Documentation/ABI/testing/sysfs-bus-mdio
@@ -7,3 +7,13 @@ Description:
 		by the device during bus enumeration, encoded in hexadecimal.
 		This ID is used to match the device with the appropriate
 		driver.
+
+What:		/sys/bus/mdio_bus/devices/.../phy_allow_suspend
+Date:		March 2014
+KernelVersion:	3.14
+Contact:	netdev at vger.kernel.org
+Description:
+		This attribute contains a boolean parameter to allow (1) or
+		deny (0) MDIO bus attached PHYs to be suspended. Some
+		bootloaders fail to properly resume a suspended PHY, so this
+		can be used to prevent the PHY from being suspended.
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 71e49000fbf3..811d35185596 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -432,8 +432,34 @@ phy_id_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(phy_id);
 
+static ssize_t phy_allow_suspend_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct phy_device *phydev = to_phy_device(dev);
+
+	return sprintf(buf, "%d\n", phydev->allow_suspend);
+}
+
+static ssize_t phy_allow_suspend_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct phy_device *phydev = to_phy_device(dev);
+	bool val;
+	int ret;
+
+	ret = strtobool(buf, &val);
+	if (ret < 0)
+		return ret;
+
+	phydev->allow_suspend = val;
+
+	return count;
+}
+static DEVICE_ATTR_RW(phy_allow_suspend);
+
 static struct attribute *mdio_dev_attrs[] = {
 	&dev_attr_phy_id.attr,
+	&dev_attr_phy_allow_suspend.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(mdio_dev);
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 4b03e63639b7..1c83d34d848b 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -173,6 +173,7 @@ struct phy_device *phy_device_create(struct mii_bus *bus, int addr, int phy_id,
 	dev->phy_id = phy_id;
 	if (c45_ids)
 		dev->c45_ids = *c45_ids;
+	dev->allow_suspend = true;
 	dev->bus = bus;
 	dev->dev.parent = bus->parent;
 	dev->dev.bus = &mdio_bus_type;
@@ -685,6 +686,10 @@ int phy_suspend(struct phy_device *phydev)
 	struct phy_driver *phydrv = to_phy_driver(phydev->dev.driver);
 	struct ethtool_wolinfo wol;
 
+	/* Do not suspend PHYs, if user disabled it */
+	if (!phydev->allow_suspend)
+		return -ENOSYS;
+
 	/* If the device has WOL enabled, we cannot suspend the PHY */
 	wol.cmd = ETHTOOL_GWOL;
 	phy_ethtool_get_wol(phydev, &wol);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 565188ca328f..c472e750c023 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -272,6 +272,7 @@ struct phy_c45_device_ids {
  * c45_ids: 802.3-c45 Device Identifers if is_c45.
  * is_c45:  Set to true if this phy uses clause 45 addressing.
  * is_internal: Set to true if this phy is internal to a MAC.
+ * allow_suspend: Set to false to prevent PHY suspend.
  * state: state of the PHY for management purposes
  * dev_flags: Device-specific flags used by the PHY driver.
  * addr: Bus address of PHY
@@ -308,6 +309,7 @@ struct phy_device {
 	struct phy_c45_device_ids c45_ids;
 	bool is_c45;
 	bool is_internal;
+	bool allow_suspend;
 
 	enum phy_state state;
 
-- 
1.8.5.3