[PATCH 1/2] net: axienet: recheck condition after timeout in mdio_wait()

[Kurt Kanzenbach]

The function could report a false positive if it gets preempted between reading
the XAE_MDIO_MCR_OFFSET register and checking for the timeout.  In such a case,
the condition has to be rechecked to avoid false positives.

Therefore, check for expected condition even after the timeout occurred.

Signed-off-by: Kurt Kanzenbach <k...@linutronix.de>
---
 drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c 
b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
index 757a3b37ae8a..4f13125e4942 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_mdio.c
@@ -21,15 +21,26 @@
 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)) {
+       u32 val;
+
+       while (1) {
+               val = axienet_ior(lp, XAE_MDIO_MCR_OFFSET);
+
+               if (val & XAE_MDIO_MCR_READY_MASK)
+                       return 0;
+
                if (time_before_eq(end, jiffies)) {
-                       WARN_ON(1);
-                       return -ETIMEDOUT;
+                       val = axienet_ior(lp, XAE_MDIO_MCR_OFFSET);
+                       break;
                }
+
                udelay(1);
        }
-       return 0;
+       if (val & XAE_MDIO_MCR_READY_MASK)
+               return 0;
+
+       WARN_ON(1);
+       return -ETIMEDOUT;
 }
 
 /**
-- 
2.11.0