net: ll_temac: Prepare indirect register access for multicast support

With .ndo_set_rx_mode/temac_set_multicast_list() being called in atomic
context (holding addr_list_lock), and temac_set_multicast_list() needing
to access temac indirect registers, the mutex used to synchronize indirect
register is a no-no.

Replace it with a spinlock, and avoid sleeping in
temac_indirect_busywait().

To avoid excessive holding of the lock, which is now a spinlock, the
temac_device_reset() function is changed to only hold the lock for short
periods.  With timeouts, it could be holding the spinlock for more than
2 seconds.
Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/xilinx/ll_temac.h

@@ -361,7 +361,7 @@ struct temac_local {
 	/* For synchronization of indirect register access.  Must be
 	 * shared mutex between interfaces in same TEMAC block.
 	 */
-	struct mutex *indirect_mutex;
+	spinlock_t *indirect_lock;
 	u32 options;			/* Current options word */
 	int last_link;
 	unsigned int temac_features;
@@ -388,8 +388,9 @@ struct temac_local {
 /* xilinx_temac.c */
 int temac_indirect_busywait(struct temac_local *lp);
 u32 temac_indirect_in32(struct temac_local *lp, int reg);
+u32 temac_indirect_in32_locked(struct temac_local *lp, int reg);
 void temac_indirect_out32(struct temac_local *lp, int reg, u32 value);
-
+void temac_indirect_out32_locked(struct temac_local *lp, int reg, u32 value);
 
 /* xilinx_temac_mdio.c */
 int temac_mdio_setup(struct temac_local *lp, struct platform_device *pdev);

drivers/net/ethernet/xilinx/ll_temac_mdio.c

@@ -25,14 +25,15 @@ static int temac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 {
 	struct temac_local *lp = bus->priv;
 	u32 rc;
+	unsigned long flags;
 
 	/* Write the PHY address to the MIIM Access Initiator register.
 	 * When the transfer completes, the PHY register value will appear
 	 * in the LSW0 register */
-	mutex_lock(lp->indirect_mutex);
+	spin_lock_irqsave(lp->indirect_lock, flags);
 	temac_iow(lp, XTE_LSW0_OFFSET, (phy_id << 5) | reg);
-	rc = temac_indirect_in32(lp, XTE_MIIMAI_OFFSET);
-	mutex_unlock(lp->indirect_mutex);
+	rc = temac_indirect_in32_locked(lp, XTE_MIIMAI_OFFSET);
+	spin_unlock_irqrestore(lp->indirect_lock, flags);
 
 	dev_dbg(lp->dev, "temac_mdio_read(phy_id=%i, reg=%x) == %x\n",
 		phy_id, reg, rc);
@@ -43,6 +44,7 @@ static int temac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 static int temac_mdio_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
 {
 	struct temac_local *lp = bus->priv;
+	unsigned long flags;
 
 	dev_dbg(lp->dev, "temac_mdio_write(phy_id=%i, reg=%x, val=%x)\n",
 		phy_id, reg, val);
@@ -50,10 +52,10 @@ static int temac_mdio_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
 	/* First write the desired value into the write data register
 	 * and then write the address into the access initiator register
 	 */
-	mutex_lock(lp->indirect_mutex);
-	temac_indirect_out32(lp, XTE_MGTDR_OFFSET, val);
-	temac_indirect_out32(lp, XTE_MIIMAI_OFFSET, (phy_id << 5) | reg);
-	mutex_unlock(lp->indirect_mutex);
+	spin_lock_irqsave(lp->indirect_lock, flags);
+	temac_indirect_out32_locked(lp, XTE_MGTDR_OFFSET, val);
+	temac_indirect_out32_locked(lp, XTE_MIIMAI_OFFSET, (phy_id << 5) | reg);
+	spin_unlock_irqrestore(lp->indirect_lock, flags);
 
 	return 0;
 }
@@ -87,9 +89,7 @@ int temac_mdio_setup(struct temac_local *lp, struct platform_device *pdev)
 
 	/* Enable the MDIO bus by asserting the enable bit and writing
 	 * in the clock config */
-	mutex_lock(lp->indirect_mutex);
 	temac_indirect_out32(lp, XTE_MC_OFFSET, 1 << 6 | clk_div);
-	mutex_unlock(lp->indirect_mutex);
 
 	bus = devm_mdiobus_alloc(&pdev->dev);
 	if (!bus)
@@ -116,10 +116,8 @@ int temac_mdio_setup(struct temac_local *lp, struct platform_device *pdev)
 	if (rc)
 		return rc;
 
-	mutex_lock(lp->indirect_mutex);
 	dev_dbg(lp->dev, "MDIO bus registered;  MC:%x\n",
 		temac_indirect_in32(lp, XTE_MC_OFFSET));
-	mutex_unlock(lp->indirect_mutex);
 	return 0;
 }
 

include/linux/platform_data/xilinx-ll-temac.h

@@ -4,6 +4,7 @@
 
 #include <linux/if_ether.h>
 #include <linux/phy.h>
+#include <linux/spinlock.h>
 
 struct ll_temac_platform_data {
 	bool txcsum;		/* Enable/disable TX checksum */
@@ -21,7 +22,7 @@ struct ll_temac_platform_data {
 	 * TEMAC IP block, the same mutex should be passed here, as
 	 * they share the same DCR bus bridge.
 	 */
-	struct mutex *indirect_mutex;
+	spinlock_t *indirect_lock;
 	/* DMA channel control setup */
 	u8 tx_irq_timeout;	/* TX Interrupt Delay Time-out */
 	u8 tx_irq_count;	/* TX Interrupt Coalescing Threshold Count */