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

[Kurt Kanzenbach]

The function could report a false positive if it gets preempted between reading
the XEL_MDIOCTRL_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_emaclite.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c 
b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
index 639e3e99af46..957d03085bd0 100644
--- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
+++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
@@ -714,19 +714,29 @@ static irqreturn_t xemaclite_interrupt(int irq, void 
*dev_id)
 static int xemaclite_mdio_wait(struct net_local *lp)
 {
        unsigned long end = jiffies + 2;
+       u32 val;
 
        /* wait for the MDIO interface to not be busy or timeout
         * after some time.
         */
-       while (xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET) &
-                       XEL_MDIOCTRL_MDIOSTS_MASK) {
+       while (1) {
+               val = xemaclite_readl(lp->base_addr + XEL_MDIOCTRL_OFFSET);
+
+               if (!(val & XEL_MDIOCTRL_MDIOSTS_MASK))
+                       return 0;
+
                if (time_before_eq(end, jiffies)) {
-                       WARN_ON(1);
-                       return -ETIMEDOUT;
+                       val = xemaclite_readl(lp->base_addr + 
XEL_MDIOCTRL_OFFSET);
+                       break;
                }
+
                msleep(1);
        }
-       return 0;
+       if (!(val & XEL_MDIOCTRL_MDIOSTS_MASK))
+               return 0;
+
+       WARN_ON(1);
+       return -ETIMEDOUT;
 }
 
 /**
-- 
2.11.0