[PATCH net-next 1/3] net: phy: add register modifying helpers returning 1 on change

[Heiner Kallweit <hkallweit1@gmail.com>]

When modifying registers there are scenarios where we need to know
whether the register content actually changed. This patch adds
new helpers to not break users of the current ones, phy_modify() etc.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/net/phy/phy-core.c | 127 ++++++++++++++++++++++++++++++++++---
 include/linux/phy.h        |  12 +++-
 2 files changed, 128 insertions(+), 11 deletions(-)

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 7d6aad287..cdea028d1 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -531,7 +531,7 @@ int phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val)
 EXPORT_SYMBOL(phy_write_mmd);
 
 /**
- * __phy_modify() - Convenience function for modifying a PHY register
+ * __phy_modify_changed() - Convenience function for modifying a PHY register
  * @phydev: a pointer to a &struct phy_device
  * @regnum: register number
  * @mask: bit mask of bits to clear
@@ -539,16 +539,69 @@ EXPORT_SYMBOL(phy_write_mmd);
  *
  * Unlocked helper function which allows a PHY register to be modified as
  * new register value = (old register value & ~mask) | set
+ *
+ * Returns negative errno, 0 if there was no change, and 1 in case of change
  */
-int __phy_modify(struct phy_device *phydev, u32 regnum, u16 mask, u16 set)
+int __phy_modify_changed(struct phy_device *phydev, u32 regnum, u16 mask,
+			 u16 set)
 {
-	int ret;
+	int new, ret;
 
 	ret = __phy_read(phydev, regnum);
 	if (ret < 0)
 		return ret;
 
-	ret = __phy_write(phydev, regnum, (ret & ~mask) | set);
+	new = (ret & ~mask) | set;
+	if (new == ret)
+		return 0;
+
+	ret = __phy_write(phydev, regnum, new);
+
+	return ret < 0 ? ret : 1;
+}
+EXPORT_SYMBOL_GPL(__phy_modify_changed);
+
+/**
+ * phy_modify_changed - Function for modifying a PHY register
+ * @phydev: the phy_device struct
+ * @regnum: register number to modify
+ * @mask: bit mask of bits to clear
+ * @set: new value of bits set in mask to write to @regnum
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ *
+ * Returns negative errno, 0 if there was no change, and 1 in case of change
+ */
+int phy_modify_changed(struct phy_device *phydev, u32 regnum, u16 mask, u16 set)
+{
+	int ret;
+
+	mutex_lock(&phydev->mdio.bus->mdio_lock);
+	ret = __phy_modify_changed(phydev, regnum, mask, set);
+	mutex_unlock(&phydev->mdio.bus->mdio_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(phy_modify_changed);
+
+/**
+ * __phy_modify - Convenience function for modifying a PHY register
+ * @phydev: the phy_device struct
+ * @regnum: register number to modify
+ * @mask: bit mask of bits to clear
+ * @set: new value of bits set in mask to write to @regnum
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int __phy_modify(struct phy_device *phydev, u32 regnum, u16 mask, u16 set)
+{
+	int ret;
+
+	ret = __phy_modify_changed(phydev, regnum, mask, set);
 
 	return ret < 0 ? ret : 0;
 }
@@ -578,7 +631,7 @@ int phy_modify(struct phy_device *phydev, u32 regnum, u16 mask, u16 set)
 EXPORT_SYMBOL_GPL(phy_modify);
 
 /**
- * __phy_modify_mmd - Convenience function for modifying a register on MMD
+ * __phy_modify_mmd_changed - Function for modifying a register on MMD
  * @phydev: the phy_device struct
  * @devad: the MMD containing register to modify
  * @regnum: register number to modify
@@ -587,17 +640,73 @@ EXPORT_SYMBOL_GPL(phy_modify);
  *
  * Unlocked helper function which allows a MMD register to be modified as
  * new register value = (old register value & ~mask) | set
+ *
+ * Returns negative errno, 0 if there was no change, and 1 in case of change
  */
-int __phy_modify_mmd(struct phy_device *phydev, int devad, u32 regnum,
-		     u16 mask, u16 set)
+int __phy_modify_mmd_changed(struct phy_device *phydev, int devad, u32 regnum,
+			     u16 mask, u16 set)
 {
-	int ret;
+	int new, ret;
 
 	ret = __phy_read_mmd(phydev, devad, regnum);
 	if (ret < 0)
 		return ret;
 
-	ret = __phy_write_mmd(phydev, devad, regnum, (ret & ~mask) | set);
+	new = (ret & ~mask) | set;
+	if (new == ret)
+		return 0;
+
+	ret = __phy_write_mmd(phydev, devad, regnum, new);
+
+	return ret < 0 ? ret : 1;
+}
+EXPORT_SYMBOL_GPL(__phy_modify_mmd_changed);
+
+/**
+ * phy_modify_mmd_changed - Function for modifying a register on MMD
+ * @phydev: the phy_device struct
+ * @devad: the MMD containing register to modify
+ * @regnum: register number to modify
+ * @mask: bit mask of bits to clear
+ * @set: new value of bits set in mask to write to @regnum
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ *
+ * Returns negative errno, 0 if there was no change, and 1 in case of change
+ */
+int phy_modify_mmd_changed(struct phy_device *phydev, int devad, u32 regnum,
+			   u16 mask, u16 set)
+{
+	int ret;
+
+	mutex_lock(&phydev->mdio.bus->mdio_lock);
+	ret = __phy_modify_mmd_changed(phydev, devad, regnum, mask, set);
+	mutex_unlock(&phydev->mdio.bus->mdio_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(phy_modify_mmd_changed);
+
+/**
+ * __phy_modify_mmd - Convenience function for modifying a register on MMD
+ * @phydev: the phy_device struct
+ * @devad: the MMD containing register to modify
+ * @regnum: register number to modify
+ * @mask: bit mask of bits to clear
+ * @set: new value of bits set in mask to write to @regnum
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int __phy_modify_mmd(struct phy_device *phydev, int devad, u32 regnum,
+		     u16 mask, u16 set)
+{
+	int ret;
+
+	ret = __phy_modify_mmd_changed(phydev, devad, regnum, mask, set);
 
 	return ret < 0 ? ret : 0;
 }
diff --git a/include/linux/phy.h b/include/linux/phy.h
index d2ffae992..378da9a61 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -799,13 +799,21 @@ int phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val);
  */
 int __phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val);
 
+int __phy_modify_changed(struct phy_device *phydev, u32 regnum, u16 mask,
+			 u16 set);
+int phy_modify_changed(struct phy_device *phydev, u32 regnum, u16 mask,
+		       u16 set);
 int __phy_modify(struct phy_device *phydev, u32 regnum, u16 mask, u16 set);
 int phy_modify(struct phy_device *phydev, u32 regnum, u16 mask, u16 set);
 
+int __phy_modify_mmd_changed(struct phy_device *phydev, int devad, u32 regnum,
+			     u16 mask, u16 set);
+int phy_modify_mmd_changed(struct phy_device *phydev, int devad, u32 regnum,
+			   u16 mask, u16 set);
 int __phy_modify_mmd(struct phy_device *phydev, int devad, u32 regnum,
-		u16 mask, u16 set);
+		     u16 mask, u16 set);
 int phy_modify_mmd(struct phy_device *phydev, int devad, u32 regnum,
-		u16 mask, u16 set);
+		   u16 mask, u16 set);
 
 /**
  * __phy_set_bits - Convenience function for setting bits in a PHY register
-- 
2.20.1