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

From: Kurt Kanzenbach
Date: Tue Oct 30 2018 - 05:31:59 EST


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 <kurt@xxxxxxxxxxxxx>
---
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