[PATCH 1/4] net: macb: Check MDIO state before read/write and use timeouts

[Harini Katakam]

From: Harini Katakam <harinik@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@xxxxxxxxxx>
Signed-off-by: Harini Katakam <harinik@xxxxxxxxxx>
---
Changes form RFC:
Cleaned up timeout implementation and moved it to a helper.

 drivers/net/ethernet/cadence/macb_main.c | 44 +++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 0acaef3..b4e26c1 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -318,10 +318,36 @@ static void macb_get_hwaddr(struct macb *bp)
 	eth_hw_addr_random(bp->dev);
 }
 
+static int macb_mdio_wait_for_idle(struct macb *bp)
+{
+	ulong timeout;
+
+	timeout = jiffies + msecs_to_jiffies(1000);
+	/* wait for end of transfer */
+	while (1) {
+		if (MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
+			break;
+
+		if (time_after_eq(jiffies, timeout)) {
+			netdev_err(bp->dev, "wait for end of transfer timed out\n");
+			return -ETIMEDOUT;
+		}
+
+		cpu_relax();
+	}
+
+	return 0;
+}
+
 static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 {
 	struct macb *bp = bus->priv;
 	int value;
+	int err;
+
+	err = macb_mdio_wait_for_idle(bp);
+	if (err < 0)
+		return err;
 
 	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
 			      | MACB_BF(RW, MACB_MAN_READ)
@@ -329,9 +355,9 @@ static int macb_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
 			      | MACB_BF(REGA, regnum)
 			      | MACB_BF(CODE, MACB_MAN_CODE)));
 
-	/* wait for end of transfer */
-	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
-		cpu_relax();
+	err = macb_mdio_wait_for_idle(bp);
+	if (err < 0)
+		return err;
 
 	value = MACB_BFEXT(DATA, macb_readl(bp, MAN));
 
@@ -342,6 +368,12 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 			   u16 value)
 {
 	struct macb *bp = bus->priv;
+	int err;
+
+
+	err = macb_mdio_wait_for_idle(bp);
+	if (err < 0)
+		return err;
 
 	macb_writel(bp, MAN, (MACB_BF(SOF, MACB_MAN_SOF)
 			      | MACB_BF(RW, MACB_MAN_WRITE)
@@ -350,9 +382,9 @@ static int macb_mdio_write(struct mii_bus *bus, int mii_id, int regnum,
 			      | MACB_BF(CODE, MACB_MAN_CODE)
 			      | MACB_BF(DATA, value)));
 
-	/* wait for end of transfer */
-	while (!MACB_BFEXT(IDLE, macb_readl(bp, NSR)))
-		cpu_relax();
+	err = macb_mdio_wait_for_idle(bp);
+	if (err < 0)
+		return err;
 
 	return 0;
 }
-- 
2.7.4