net/fsl_pq_mdio: use spin_event_timeout() to poll the indicator register

Macro spin_event_timeout() was designed for simple polling of hardware
registers with a timeout, so use it when we poll the MIIMIND register.
This allows us to return an error code instead of polling indefinitely.

Note that PHY_INIT_TIMEOUT is a count of loop iterations, so we can't use
it for spin_event_timeout(), which asks for microseconds.
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fsl_pq_mdio.c

@@ -47,6 +47,9 @@
 #include "gianfar.h"
 #include "fsl_pq_mdio.h"
 
+/* Number of microseconds to wait for an MII register to respond */
+#define MII_TIMEOUT	1000
+
 struct fsl_pq_mdio_priv {
 	void __iomem *map;
 	struct fsl_pq_mdio __iomem *regs;
@@ -64,6 +67,8 @@ struct fsl_pq_mdio_priv {
 int fsl_pq_local_mdio_write(struct fsl_pq_mdio __iomem *regs, int mii_id,
 		int regnum, u16 value)
 {
+	u32 status;
+
 	/* Set the PHY address and the register address we want to write */
 	out_be32(&regs->miimadd, (mii_id << 8) | regnum);
 
@@ -71,10 +76,10 @@ int fsl_pq_local_mdio_write(struct fsl_pq_mdio __iomem *regs, int mii_id,
 	out_be32(&regs->miimcon, value);
 
 	/* Wait for the transaction to finish */
-	while (in_be32(&regs->miimind) & MIIMIND_BUSY)
-		cpu_relax();
+	status = spin_event_timeout(!(in_be32(&regs->miimind) &	MIIMIND_BUSY),
+				    MII_TIMEOUT, 0);
 
-	return 0;
+	return status ? 0 : -ETIMEDOUT;
 }
 
 /*
@@ -91,6 +96,7 @@ int fsl_pq_local_mdio_read(struct fsl_pq_mdio __iomem *regs,
 		int mii_id, int regnum)
 {
 	u16 value;
+	u32 status;
 
 	/* Set the PHY address and the register address we want to read */
 	out_be32(&regs->miimadd, (mii_id << 8) | regnum);
@@ -99,9 +105,12 @@ int fsl_pq_local_mdio_read(struct fsl_pq_mdio __iomem *regs,
 	out_be32(&regs->miimcom, 0);
 	out_be32(&regs->miimcom, MII_READ_COMMAND);
 
-	/* Wait for the transaction to finish */
-	while (in_be32(&regs->miimind) & (MIIMIND_NOTVALID | MIIMIND_BUSY))
-		cpu_relax();
+	/* Wait for the transaction to finish, normally less than 100us */
+	status = spin_event_timeout(!(in_be32(&regs->miimind) &
+				    (MIIMIND_NOTVALID | MIIMIND_BUSY)),
+				    MII_TIMEOUT, 0);
+	if (!status)
+		return -ETIMEDOUT;
 
 	/* Grab the value of the register from miimstat */
 	value = in_be32(&regs->miimstat);
@@ -144,7 +153,7 @@ int fsl_pq_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 static int fsl_pq_mdio_reset(struct mii_bus *bus)
 {
 	struct fsl_pq_mdio __iomem *regs = fsl_pq_mdio_get_regs(bus);
-	int timeout = PHY_INIT_TIMEOUT;
+	u32 status;
 
 	mutex_lock(&bus->mdio_lock);
 
@@ -155,12 +164,12 @@ static int fsl_pq_mdio_reset(struct mii_bus *bus)
 	out_be32(&regs->miimcfg, MIIMCFG_INIT_VALUE);
 
 	/* Wait until the bus is free */
-	while ((in_be32(&regs->miimind) & MIIMIND_BUSY) && timeout--)
-		cpu_relax();
+	status = spin_event_timeout(!(in_be32(&regs->miimind) &	MIIMIND_BUSY),
+				    MII_TIMEOUT, 0);
 
 	mutex_unlock(&bus->mdio_lock);
 
-	if (timeout < 0) {
+	if (!status) {
 		printk(KERN_ERR "%s: The MII Bus is stuck!\n",
 				bus->name);
 		return -EBUSY;