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Date:   Sun, 19 May 2019 19:59:36 +0200
From:   Benedikt Spranger <b.spranger@...utronix.de>
To:     netdev@...r.kernel.org
Cc:     Kurt Kanzenbach <kurt@...utronix.de>
Subject: [[PATCH net-next] 1/2] net: axienet: use readx_poll_timeout() in mdio wait function

From: Kurt Kanzenbach <kurt@...utronix.de>

On loaded systems with a preemptible kernel the mdio_wait() function may
report an error while everything is working fine:

axienet_mdio_wait_until_ready():
  axienet_ior() -> chip not ready
  --> interrupt here (other work for some time / chip become ready)
  if (time_before_eq(end, jiffies))
    --> false positive error report

Replace the current code with readx_poll_timeout() which take care
of the situation.

Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
Signed-off-by: Benedikt Spranger <b.spranger@...utronix.de>
---
 drivers/net/ethernet/xilinx/xilinx_axienet.h     |  5 +++++
 .../net/ethernet/xilinx/xilinx_axienet_mdio.c    | 16 ++++++----------
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
index c337400485da..011adae32b89 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
@@ -484,6 +484,11 @@ static inline u32 axienet_ior(struct axienet_local *lp, off_t offset)
 	return in_be32(lp->regs + offset);
 }
 
+static inline u32 axinet_ior_read_mcr(struct axienet_local *lp)
+{
+	return axienet_ior(lp, XAE_MDIO_MCR_OFFSET);
+}
+
 /**
  * axienet_iow - Memory mapped Axi Ethernet register write
  * @lp:         Pointer to axienet local structure
diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
index 757a3b37ae8a..704babdbc8a2 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
@@ -11,6 +11,7 @@
 #include <linux/of_address.h>
 #include <linux/of_mdio.h>
 #include <linux/jiffies.h>
+#include <linux/iopoll.h>
 
 #include "xilinx_axienet.h"
 
@@ -20,16 +21,11 @@
 /* Wait till MDIO interface is ready to accept a new transaction.*/
 int axienet_mdio_wait_until_ready(struct axienet_local *lp)
 {
-	unsigned long end = jiffies + 2;
-	while (!(axienet_ior(lp, XAE_MDIO_MCR_OFFSET) &
-		 XAE_MDIO_MCR_READY_MASK)) {
-		if (time_before_eq(end, jiffies)) {
-			WARN_ON(1);
-			return -ETIMEDOUT;
-		}
-		udelay(1);
-	}
-	return 0;
+	u32 val;
+
+	return readx_poll_timeout(axinet_ior_read_mcr, lp,
+				  val, val & XAE_MDIO_MCR_READY_MASK,
+				  1, 20000);
 }
 
 /**
-- 
2.20.1

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