[PATCH net-next v2] net: mvpp2: tai: warn once if we fail to update our timestamp

[Russell King <rmk+kernel@armlinux.org.uk>]

The hardware timestamps for packets contain a truncated seconds field,
only containing two bits of seconds. In order to provide the full
number of seconds, we need to keep track of the full hardware clock by
reading it every two seconds.

However, if we fail to read the clock, we silently ignore the error.
Print a warning indicating that the PP2 TAI clock timestamps have
become unreliable.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
--
v2: correct dev_warn_once() indentation
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
index 95862aff49f1..6b60beb1f3ed 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
@@ -54,6 +54,7 @@
 #define TCSR_CAPTURE_0_VALID		BIT(0)
 
 struct mvpp2_tai {
+	struct device *dev;
 	struct ptp_clock_info caps;
 	struct ptp_clock *ptp_clock;
 	void __iomem *base;
@@ -303,7 +304,8 @@ static long mvpp22_tai_aux_work(struct ptp_clock_info *ptp)
 {
 	struct mvpp2_tai *tai = ptp_to_tai(ptp);
 
-	mvpp22_tai_gettimex64(ptp, &tai->stamp, NULL);
+	if (mvpp22_tai_gettimex64(ptp, &tai->stamp, NULL) < 0)
+		dev_warn_once(tai->dev, "PTP timestamps are unreliable");
 
 	return msecs_to_jiffies(2000);
 }
@@ -401,6 +403,7 @@ int mvpp22_tai_probe(struct device *dev, struct mvpp2 *priv)
 
 	spin_lock_init(&tai->lock);
 
+	tai->dev = dev;
 	tai->base = priv->iface_base;
 
 	/* The step size consists of three registers - a 16-bit nanosecond step
-- 
2.30.2