linux-kernel - [PATCH 1/3] net: phy: Add nested variants of mdiobus read/write

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Message-ID: <5628A05D.3020104@baylibre.com>
Date:	Thu, 22 Oct 2015 10:37:49 +0200
From:	Neil Armstrong <narmstrong@...libre.com>
To:	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	vivien.didelot@...oirfairelinux.com, Andrew Lunn <andrew@...n.ch>,
	Fabian Frederick <fabf@...net.be>,
	Pavel Nakonechny <pavel.nakonechny@...tlab.ru>,
	Joe Perches <joe@...ches.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, nbd@...nwrt.org,
	sergei.shtylyov@...entembedded.com
Subject: [PATCH 1/3] net: phy: Add nested variants of mdiobus read/write

Since nested variants of mdiobus_read/write are used in multiple
drivers, add nested variants in the mdiobus core.

Suggested-by: Andrew Lunn <andrew@...n.ch>
Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
---
 drivers/net/phy/mdio_bus.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/phy.h        |  2 ++
 2 files changed, 57 insertions(+)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 12f44c5..88cb459 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -372,6 +372,33 @@ struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr)
 EXPORT_SYMBOL(mdiobus_scan);

 /**
+ * mdiobus_read_nested - Nested version of the mdiobus_read function
+ * @bus: the mii_bus struct
+ * @addr: the phy address
+ * @regnum: register number to read
+ *
+ * In case of nested MDIO bus access avoid lockdep false positives by
+ * using mutex_lock_nested().
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int mdiobus_read_nested(struct mii_bus *bus, int addr, u32 regnum)
+{
+	int retval;
+
+	BUG_ON(in_interrupt());
+
+	mutex_lock_nested(&bus->mdio_lock, SINGLE_DEPTH_NESTING);
+	retval = bus->read(bus, addr, regnum);
+	mutex_unlock(&bus->mdio_lock);
+
+	return retval;
+}
+EXPORT_SYMBOL(mdiobus_read_nested);
+
+/**
  * mdiobus_read - Convenience function for reading a given MII mgmt register
  * @bus: the mii_bus struct
  * @addr: the phy address
@@ -396,6 +423,34 @@ int mdiobus_read(struct mii_bus *bus, int addr, u32 regnum)
 EXPORT_SYMBOL(mdiobus_read);

 /**
+ * mdiobus_write_nested - Nested version of the mdiobus_write function
+ * @bus: the mii_bus struct
+ * @addr: the phy address
+ * @regnum: register number to write
+ * @val: value to write to @regnum
+ *
+ * In case of nested MDIO bus access avoid lockdep false positives by
+ * using mutex_lock_nested().
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int mdiobus_write_nested(struct mii_bus *bus, int addr, u32 regnum, u16 val)
+{
+	int err;
+
+	BUG_ON(in_interrupt());
+
+	mutex_lock_nested(&bus->mdio_lock, SINGLE_DEPTH_NESTING);
+	err = bus->write(bus, addr, regnum, val);
+	mutex_unlock(&bus->mdio_lock);
+
+	return err;
+}
+EXPORT_SYMBOL(mdiobus_write_nested);
+
+/**
  * mdiobus_write - Convenience function for writing a given MII mgmt register
  * @bus: the mii_bus struct
  * @addr: the phy address
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 4c477e6..05fde31 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -213,7 +213,9 @@ static inline struct mii_bus *devm_mdiobus_alloc(struct device *dev)
 void devm_mdiobus_free(struct device *dev, struct mii_bus *bus);
 struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr);
 int mdiobus_read(struct mii_bus *bus, int addr, u32 regnum);
+int mdiobus_read_nested(struct mii_bus *bus, int addr, u32 regnum);
 int mdiobus_write(struct mii_bus *bus, int addr, u32 regnum, u16 val);
+int mdiobus_write_nested(struct mii_bus *bus, int addr, u32 regnum, u16 val);


 #define PHY_INTERRUPT_DISABLED	0x0
-- 
1.9.1
--
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