net: enetc: remove ERR050089 workaround for i.MX95

The ERR050089 workaround causes performance degradation and potential
functional issues (e.g., RCU stalls) under certain workloads. Since
new SoCs like i.MX95 do not require this workaround, use a static key
to compile out enetc_lock_mdio() and enetc_unlock_mdio() at runtime,
improving performance and avoiding unnecessary logic.

Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: Wei Fang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: vladimiroltean

drivers/net/ethernet/freescale/enetc/enetc_hw.h

@@ -396,18 +396,22 @@ struct enetc_hw {
  */
 extern rwlock_t enetc_mdio_lock;
 
+DECLARE_STATIC_KEY_FALSE(enetc_has_err050089);
+
 /* use this locking primitive only on the fast datapath to
  * group together multiple non-MDIO register accesses to
  * minimize the overhead of the lock
  */
 static inline void enetc_lock_mdio(void)
 {
-	read_lock(&enetc_mdio_lock);
+	if (static_branch_unlikely(&enetc_has_err050089))
+		read_lock(&enetc_mdio_lock);
 }
 
 static inline void enetc_unlock_mdio(void)
 {
-	read_unlock(&enetc_mdio_lock);
+	if (static_branch_unlikely(&enetc_has_err050089))
+		read_unlock(&enetc_mdio_lock);
 }
 
 /* use these accessors only on the fast datapath under
@@ -416,14 +420,16 @@ static inline void enetc_unlock_mdio(void)
  */
 static inline u32 enetc_rd_reg_hot(void __iomem *reg)
 {
-	lockdep_assert_held(&enetc_mdio_lock);
+	if (static_branch_unlikely(&enetc_has_err050089))
+		lockdep_assert_held(&enetc_mdio_lock);
 
 	return ioread32(reg);
 }
 
 static inline void enetc_wr_reg_hot(void __iomem *reg, u32 val)
 {
-	lockdep_assert_held(&enetc_mdio_lock);
+	if (static_branch_unlikely(&enetc_has_err050089))
+		lockdep_assert_held(&enetc_mdio_lock);
 
 	iowrite32(val, reg);
 }
@@ -452,9 +458,13 @@ static inline u32 _enetc_rd_mdio_reg_wa(void __iomem *reg)
 	unsigned long flags;
 	u32 val;
 
-	write_lock_irqsave(&enetc_mdio_lock, flags);
-	val = ioread32(reg);
-	write_unlock_irqrestore(&enetc_mdio_lock, flags);
+	if (static_branch_unlikely(&enetc_has_err050089)) {
+		write_lock_irqsave(&enetc_mdio_lock, flags);
+		val = ioread32(reg);
+		write_unlock_irqrestore(&enetc_mdio_lock, flags);
+	} else {
+		val = ioread32(reg);
+	}
 
 	return val;
 }
@@ -463,9 +473,13 @@ static inline void _enetc_wr_mdio_reg_wa(void __iomem *reg, u32 val)
 {
 	unsigned long flags;
 
-	write_lock_irqsave(&enetc_mdio_lock, flags);
-	iowrite32(val, reg);
-	write_unlock_irqrestore(&enetc_mdio_lock, flags);
+	if (static_branch_unlikely(&enetc_has_err050089)) {
+		write_lock_irqsave(&enetc_mdio_lock, flags);
+		iowrite32(val, reg);
+		write_unlock_irqrestore(&enetc_mdio_lock, flags);
+	} else {
+		iowrite32(val, reg);
+	}
 }
 
 #ifdef ioread64

drivers/net/ethernet/freescale/enetc/enetc_pci_mdio.c

@@ -9,6 +9,28 @@
 #define ENETC_MDIO_BUS_NAME	ENETC_MDIO_DEV_NAME " Bus"
 #define ENETC_MDIO_DRV_NAME	ENETC_MDIO_DEV_NAME " driver"
 
+DEFINE_STATIC_KEY_FALSE(enetc_has_err050089);
+EXPORT_SYMBOL_GPL(enetc_has_err050089);
+
+static void enetc_emdio_enable_err050089(struct pci_dev *pdev)
+{
+	if (pdev->vendor == PCI_VENDOR_ID_FREESCALE &&
+	    pdev->device == ENETC_MDIO_DEV_ID) {
+		static_branch_inc(&enetc_has_err050089);
+		dev_info(&pdev->dev, "Enabled ERR050089 workaround\n");
+	}
+}
+
+static void enetc_emdio_disable_err050089(struct pci_dev *pdev)
+{
+	if (pdev->vendor == PCI_VENDOR_ID_FREESCALE &&
+	    pdev->device == ENETC_MDIO_DEV_ID) {
+		static_branch_dec(&enetc_has_err050089);
+		if (!static_key_enabled(&enetc_has_err050089.key))
+			dev_info(&pdev->dev, "Disabled ERR050089 workaround\n");
+	}
+}
+
 static int enetc_pci_mdio_probe(struct pci_dev *pdev,
 				const struct pci_device_id *ent)
 {
@@ -62,6 +84,8 @@ static int enetc_pci_mdio_probe(struct pci_dev *pdev,
 		goto err_pci_mem_reg;
 	}
 
+	enetc_emdio_enable_err050089(pdev);
+
 	err = of_mdiobus_register(bus, dev->of_node);
 	if (err)
 		goto err_mdiobus_reg;
@@ -71,6 +95,7 @@ static int enetc_pci_mdio_probe(struct pci_dev *pdev,
 	return 0;
 
 err_mdiobus_reg:
+	enetc_emdio_disable_err050089(pdev);
 	pci_release_region(pdev, 0);
 err_pci_mem_reg:
 	pci_disable_device(pdev);
@@ -88,6 +113,9 @@ static void enetc_pci_mdio_remove(struct pci_dev *pdev)
 	struct enetc_mdio_priv *mdio_priv;
 
 	mdiobus_unregister(bus);
+
+	enetc_emdio_disable_err050089(pdev);
+
 	mdio_priv = bus->priv;
 	iounmap(mdio_priv->hw->port);
 	pci_release_region(pdev, 0);