drivers: net: davinci_mdio: prevent spurious timeout

A well timed kernel preemption in the time_after() loop
in wait_for_idle() can result in a spurious timeout
error to be returned.

Fix it by using readl_poll_timeout() which takes care of
this issue.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c
index 3c33f4504d8e23f45e6b7668f20b1c399d5806f6..98a1c97fb95e8a4964c188db7aa53dba77cf37a3 100644 (file)
--- a/drivers/net/ethernet/ti/davinci_mdio.c
+++ b/drivers/net/ethernet/ti/davinci_mdio.c
@@ -34,6 +34,7 @@
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/pm_runtime.h>
 #include <linux/davinci_emac.h>
 #include <linux/of.h>
@@ -227,14 +228,14 @@ static inline int wait_for_user_access(struct davinci_mdio_data *data)
 static inline int wait_for_idle(struct davinci_mdio_data *data)
 {
        struct davinci_mdio_regs __iomem *regs = data->regs;
-       unsigned long timeout = jiffies + msecs_to_jiffies(MDIO_TIMEOUT);
+       u32 val, ret;
 
-       while (time_after(timeout, jiffies)) {
-               if (__raw_readl(&regs->control) & CONTROL_IDLE)
-                       return 0;
-       }
-       dev_err(data->dev, "timed out waiting for idle\n");
-       return -ETIMEDOUT;
+       ret = readl_poll_timeout(&regs->control, val, val & CONTROL_IDLE,
+                                0, MDIO_TIMEOUT * 1000);
+       if (ret)
+               dev_err(data->dev, "timed out waiting for idle\n");
+
+       return ret;
 }
 
 static int davinci_mdio_read(struct mii_bus *bus, int phy_id, int phy_reg)