[RFC PATCH 1/5] net: macb: Check MDIO state before read/write and use timeouts

[<harinikatakamlinux@gmail.com>]

From: Harini Katakam <harinik@xilinx.com>

Replace the while loop in MDIO read/write functions with a timeout.
In addition, add a check for MDIO bus busy before initiating a new
operation as well to make sure there is no ongoing MDIO operation.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Harini Katakam <harinik@xilinx.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 54 ++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index d09bd43..f4030c1 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -321,6 +321,21 @@ static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 {
 	struct macb *bp = bus->priv;
 	int value;
+	ulong timeout;
+
+	timeout = jiffies + msecs_to_jiffies(1000);
+	/* wait for end of transfer */
+	do {
+		if (MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+			break;
+
+		cpu_relax();
+	} while (!time_after_eq(jiffies, timeout));
+
+	if (time_after_eq(jiffies, timeout)) {
+		netdev_err(bp->dev, "wait for end of transfer timed out\n");
+		return -ETIMEDOUT;
+	}
 
 	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
 			      | MACB_BF(RW, MACB_MAN_READ)
@@ -328,9 +343,19 @@ static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 			      | MACB_BF(REGA, regnum)
 			      | MACB_BF(CODE, MACB_MAN_CODE)));
 
+	timeout = jiffies + msecs_to_jiffies(1000);
 	/* wait for end of transfer */
-	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+	do {
+		if (MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+			break;
+
 		cpu_relax();
+	} while (!time_after_eq(jiffies, timeout));
+
+	if (time_after_eq(jiffies, timeout)) {
+		netdev_err(bp->dev, "wait for end of transfer timed out\n");
+		return -ETIMEDOUT;
+	}
 
 	value = MACB_BFEXT(DATA, macb_readl(bp, MAN));
 
@@ -341,6 +366,21 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 			   u16 value)
 {
 	struct macb *bp = bus->priv;
+	ulong timeout;
+
+	timeout = jiffies + msecs_to_jiffies(1000);
+	/* wait for end of transfer */
+	do {
+		if (MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+			break;
+
+		cpu_relax();
+	} while (!time_after_eq(jiffies, timeout));
+
+	if (time_after_eq(jiffies, timeout)) {
+		netdev_err(bp->dev, "wait for end of transfer timed out\n");
+		return -ETIMEDOUT;
+	}
 
 	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
 			      | MACB_BF(RW, MACB_MAN_WRITE)
@@ -349,9 +389,19 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 			      | MACB_BF(CODE, MACB_MAN_CODE)
 			      | MACB_BF(DATA, value)));
 
+	timeout = jiffies + msecs_to_jiffies(1000);
 	/* wait for end of transfer */
-	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+	do {
+		if (MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+			break;
+
 		cpu_relax();
+	} while (!time_after_eq(jiffies, timeout));
+
+	if (time_after_eq(jiffies, timeout)) {
+		netdev_err(bp->dev, "wait for end of transfer timed out\n");
+		return -ETIMEDOUT;
+	}
 
 	return 0;
 }
-- 
2.7.4