net: macb: Check MDIO state before read/write and use timeouts

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: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb.h

@@ -715,6 +715,8 @@
 		__v; \
 	})
 
+#define MACB_READ_NSR(bp)	macb_readl(bp, NSR)
+
 /* struct macb_dma_desc - Hardware DMA descriptor
  * @addr: DMA address of data buffer
  * @ctrl: Control and status bits

drivers/net/ethernet/cadence/macb_main.c

@@ -36,6 +36,7 @@
 #include <linux/ip.h>
 #include <linux/udp.h>
 #include <linux/tcp.h>
+#include <linux/iopoll.h>
 #include "macb.h"
 
 #define MACB_RX_BUFFER_SIZE	128
@@ -79,6 +80,8 @@
  */
 #define MACB_HALT_TIMEOUT	1230
 
+#define MACB_MDIO_TIMEOUT	1000000 /* in usecs */
+
 /* DMA buffer descriptor might be different size
  * depends on hardware configuration:
  *
@@ -318,10 +321,23 @@ static void macb_get_hwaddr(struct macb *bp)
 	eth_hw_addr_random(bp->dev);
 }
 
+static int macb_mdio_wait_for_idle(struct macb *bp)
+{
+	u32 val;
+
+	return readx_poll_timeout(MACB_READ_NSR, bp, val, val & MACB_BIT(IDLE),
+				  1, MACB_MDIO_TIMEOUT);
+}
+
 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 +345,9 @@ 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 +358,11 @@ 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 +371,9 @@ 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;
 }